Neuropeptide Y expression defines a novel class of GABAergic projection neuron in the inferior colliculus.
Located in the midbrain, the inferior colliculus (IC) integrates information from numerous auditory nuclei and is an important hub for sound processing. Despite its importance, little is known about the molecular identity and functional roles of defined neuron types in the IC. Using a multifaceted approach in mice of both sexes, we found that neuropeptide Y (NPY) expression identifies a major class of inhibitory neurons, accounting for approximately one-third of GABAergic neurons in the IC. Retrograde tracing showed that NPY neurons are principal neurons that can project to the medial geniculate nucleus. In brain slice recordings, many NPY neurons fired spontaneously, suggesting that NPY neurons may drive tonic inhibition onto postsynaptic targets. Morphological reconstructions showed that NPY neurons are stellate cells, and the dendrites of NPY neurons in the tonotopically-organized central nucleus of the IC cross isofrequency laminae. Immunostaining confirmed that NPY neurons express NPY, and we therefore hypothesized that NPY signaling regulates activity in the IC. In crosses between Npy1r(cre) and Ai14 Cre-reporter mice, we found that NPY Y1 receptor (Y1R)-expressing neurons are glutamatergic and were broadly distributed throughout the rostro-caudal extent of the IC. In whole-cell recordings, application of a high affinity Y1R agonist led to hyperpolarization in most
Silveira Marina A; Anair Justin D; Beebe Nichole L; Mirjalili Pooyan; Schofield Brett R; Roberts Michael T
The Journal of neuroscience : the official journal of the Society for Neuroscience
2020
2020-05-06
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
journalArticle
<a href="http://doi.org/10.1523/JNEUROSCI.0420-20.2020" target="_blank" rel="noreferrer noopener">10.1523/JNEUROSCI.0420-20.2020</a>
Perineuronal nets and subtypes of GABAergic cells differentiate auditory and multisensory nuclei in the intercollicular area of the midbrain.
ab_10807945; ab_141607; ab_2278725; ab_2336066; ab_2336132; ab_2336874; ab_2336875; ab_2336881; ab_2534012; ab_2535710; ab_2665454; ab_2735091; ascending projections; descending projections; dorsal column nuclei; efferent connections; external nucleus; extracellular-matrix; Guinea pigs; inferior colliculus; intercollicular tegmentum; lateral lemniscus; medial geniculate-body; nucleus of the brachium of the inferior colliculus; nucleus of the brachium of the inferior colliculus; rostral pole of the inferior colliculus; rrid; RRID: AB_10807945; RRID: AB_141607; RRID: AB_2278725; RRID: AB_2336066; RRID: AB_2336132; RRID: AB_2336874; RRID: AB_2336875; RRID: AB_2336881; RRID: AB_2534012; RRID: AB_2535710; RRID: AB_2665454; RRID: AB_2735091; RRID: SCR_001775; scr_001775; superior colliculus; VGLUT2; VGLUT2
The intercollicular region, which lies between the inferior and superior colliculi in the midbrain, contains neurons that respond to auditory, visual, and somatosensory stimuli. Golgi studies have been used to parse this region into three distinct nuclei: the intercollicular tegmentum (ICt), the rostral pole of the inferior colliculus (ICrp), and the nucleus of the brachium of the IC (NBIC). Few reports have focused on these nuclei, especially the ICt and the ICrp, possibly due to lack of a marker that distinguishes these areas and is compatible with modern methods. Here, we found that staining for GABAergic cells and perineuronal nets differentiates these intercollicular nuclei in guinea pigs. Further, we found that the proportions of four subtypes of GABAergic cells differentiate intercollicular nuclei from each other and from adjacent inferior collicular subdivisions. Our results support earlier studies that suggest distinct morphology and functions for intercollicular nuclei, and provide staining methods that differentiate intercollicular nuclei and are compatible with most modern techniques. We hope that this will help future studies to further characterize the intercollicular region.
Beebe Nichole L; Noftz William A; Schofield Brett R
The Journal of comparative neurology
2020
2020-04-17
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
journalArticle
<a href="http://doi.org/10.1002/cne.24926" target="_blank" rel="noreferrer noopener">10.1002/cne.24926</a>
Generation of a ChAT(Cre) mouse line without the early onset hearing loss typical of the C57BL/6J strain.
Acetylcholine; Age-related hearing loss; Presbycusis; Choline acetyltransferase; Normal hearing; Transgenic mouse
The development of knockin mice with Cre recombinase expressed under the control of the promoter for choline acetyltransferase (ChAT) has allowed experimental manipulation of cholinergic circuits. However, currently available ChAT(Cre) mouse lines are on the C57BL/6J strain background, which shows early onset age-related hearing loss attributed to the Cdh23(753A) mutation (a.k.a., the ahl mutation). To develop ChAT(Cre) mice without accelerated hearing loss, we backcrossed ChAT(IRES-Cre) mice with CBA/CaJ mice that have normal hearing. We used genotyping to obtain mice homozygous for ChAT(IRES-Cre) and the wild-type allele at the Cdh23 locus (ChAT(Cre,Cdh23WT)). In the new line, auditory brainstem response thresholds were approximately 20 dB lower than those in 9 month old ChAT(IRES-Cre) mice at all frequencies tested (4-31.5 kHz). These thresholds were stable throughout the period of testing (3-12 months of age). We then bred ChAT(Cre,Cdh23WT) animals with Ai14 reporter mice to confirm the expression pattern of ChAT(Cre). In these mice, tdTomato-labeled cells were observed in all brainstem regions known to contain cholinergic cells. We then stained the tissue with a neuron-specific marker, NeuN, to determine whether Cre expression was limited to neurons. Across several brainstem nuclei (pontomesencephalic tegmentum, motor trigeminal and facial nuclei), 100% of the tdTomato-labeled cells were double-labeled with anti-NeuN (n = 1896 cells), indicating Cre-recombinase was limited to neurons. Almost all of these cells (1867/1896 = 98.5%) also stained with antibodies against ChAT, indicating that reporter label was expressed almost exclusively in cholinergic neurons. Finally, an average 88.7% of the ChAT+ cells in these nuclei were labeled with tdTomato, indicating that the Cre is expressed in a large proportion of the cholinergic cells in these nuclei. We conclude that the backcrossed ChAT(Cre,Cdh23WT) mouse line has normal hearing and expresses Cre recombinase almost exclusively in cholinergic neurons. This ChAT(Cre,Cdh23WT) mouse line may provide an opportunity to manipulate cholinergic circuits without the confound of accelerated hearing loss associated with the C57BL/6J background. Furthermore, comparison with lines that do show early hearing loss may provide insight into possible cholinergic roles in age-related hearing loss.
Beebe Nichole L; Sowick Colleen S; Kristaponyte Inga; Galazyuk Alexander V; Vetter Douglas E; Cox Brandon C; Schofield Brett R
Hearing research
2020
2020-03
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
Journal Article
<a href="http://doi.org/10.1016/j.heares.2020.107896" target="_blank" rel="noreferrer noopener">10.1016/j.heares.2020.107896</a>
A novel class of inferior colliculus principal neurons labeled in vasoactive intestinal peptide-Cre mice
auditory; Inferior colliculus; mouse; neural circuits; neuron types; neuroscience; optogenetics; VIP
Located in the midbrain, the inferior colliculus (IC) is the hub of the central auditory system. Although the IC plays important roles in speech processing, sound localization, and other auditory computations, the organization of the IC microcircuitry remains largely unknown. Using a multifaceted approach in mice, we have identified vasoactive intestinal peptide (VIP) neurons as a novel class of IC principal neurons. VIP neurons are glutamatergic stellate cells with sustained firing patterns. Their extensive axons project to long-range targets including the auditory thalamus, auditory brainstem, superior colliculus, and periaqueductal gray. Using optogenetic circuit mapping, we found that VIP neurons integrate input from the contralateral IC and the dorsal cochlear nucleus. The dorsal cochlear nucleus also drove feedforward inhibition to VIP neurons, indicating that inhibitory circuits within the IC shape the temporal integration of ascending inputs. Thus, VIP neurons are well-positioned to influence auditory computations in a number of brain regions.
Goyer David; Silveira Marina A; George Alexander P; Beebe Nichole L; Edelbrock Ryan M; Malinski Peter T; Schofield Brett R; Roberts Michael T
eLife
2019
2019-04
<a href="http://doi.org/10.7554/eLife.43770" target="_blank" rel="noreferrer noopener">10.7554/eLife.43770</a>
Subtypes of GABAergic cells in the inferior colliculus
Auditory system; Cell type; GABA; Inhibition; Perineuronal net
The inferior colliculus occupies a central position in ascending and descending auditory pathways. A substantial proportion of its neurons are GABAergic, and these neurons contribute to intracollicular circuits as well as to extrinsic projections to numerous targets. A variety of types of evidence - morphology, physiology, molecular markers - indicate that the GABAergic cells can be divided into at least four subtypes that serve different functions. However, there has yet to emerge a unified scheme for distinguishing these subtypes. The present review discusses these criteria and, where possible, relates the different properties. In contrast to GABAergic cells in cerebral cortex, where subtypes are much more thoroughly characterized, those in the inferior colliculus contribute substantially to numerous long range extrinsic projections. At present, the best characterized subtype is a GABAergic cell with a large soma, dense perisomatic synaptic inputs and a large axon that provides rapid auditory input to the thalamus. This large GABAergic subtype projects to additional targets, and other subtypes also project to the thalamus. The eventual characterization of these subtypes can be expected to reveal multiple functions of these inhibitory cells and the many circuits to which they contribute.
Schofield Brett R; Beebe Nichole L
Hearing Research
2019
2019-05
<a href="http://doi.org/10.1016/j.heares.2018.10.001" target="_blank" rel="noreferrer noopener">10.1016/j.heares.2018.10.001</a>
Bilateral projections to the thalamus from individual neurons in the inferior colliculus.
collateral; GABA; inferior colliculus; medial geniculate body; RRID:AB2278725; RRID:AB260754; synchronization
The medial geniculate body (MG) receives a large input from the ipsilateral inferior colliculus (IC) and a smaller but substantial input from the contralateral IC. Both crossed and uncrossed inputs comprise a large percentage of glutamatergic cells and a smaller percentage of GABAergic cells. We used double labeling with fluorescent retrograde tracers to identify individual IC cells that project bilaterally to the MGs in adult guinea pigs. We also used immunohistochemistry for glutamic acid decarboxylase to distinguish GABAergic from glutamatergic cells that project bilaterally to the MG. We found cells in the IC that contained both retrograde tracers, indicating that they project bilaterally. Across cases, the bilaterally projecting cells constituted up to 37% of the cells that project to the ipsilateral MG and up to 73% of the cells that project to the contralateral MG. GABAergic cells averaged 20% of the bilaterally-projecting population. We conclude that a population of IC cells sends branching axonal projections to innervate the MG bilaterally. Most of the neurons in this population are glutamatergic, with a minority that are GABAergic. A mixed projection, with glutamatergic cells outnumbering GABAergic cells, originates from each of the major IC subdivisions (central nucleus, dorsal cortex, and lateral cortex). The bilaterally projecting cells are likely to serve functions different from the larger unilateral projections, perhaps synchronizing activity on the two sides of the auditory brain.
Mellott Jeffrey G; Beebe Nichole L; Schofield Brett R
The Journal of comparative neurology
2019
2019-04
<a href="http://doi.org/10.1002/cne.24600" target="_blank" rel="noreferrer noopener">10.1002/cne.24600</a>
Descending projections from auditory cortex to excitatory and inhibitory cells in the nucleus of the brachium of the inferior colliculus.
GABA; ascending; corticofugal; medial geniculate nucleus; modulation
Descending projections from the auditory cortex (AC) terminate in subcortical auditory centers from the medial geniculate nucleus (MG) to the cochlear nucleus, allowing the AC to modulate the processing of acoustic information at many levels of the auditory system. The nucleus of the brachium of the inferior colliculus (NBIC) is a large midbrain auditory nucleus that is a target of these descending cortical projections. The NBIC is a source of several auditory projections, including an ascending projection to the MG. This ascending projection appears to originate from both excitatory and inhibitory NBIC cells, but whether the cortical projections contact either of these cell groups is unknown. In this study, we first combined retrograde tracing and immunochemistry for glutamic acid decarboxylase (GAD, a marker of GABAergic cells) to identify GABAergic and non-GABAergic NBIC projections to the MG. Our first result is that
Mellott Jeffrey G; Bickford Martha E; Schofield Brett R
Frontiers in systems neuroscience
2014
1905-07
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.3389/fnsys.2014.00188" target="_blank" rel="noreferrer noopener">10.3389/fnsys.2014.00188</a>
Excitatory and inhibitory projections in parallel pathways from the inferior colliculus to the auditory thalamus.
GABA; auditory system; GAD; lemniscal; medial geniculate; non-lemniscal; tectothalamic
Individual subdivisions of the medial geniculate body (MG) receive a majority of their ascending inputs from 1 or 2 subdivisions of the inferior colliculus (IC). This establishes parallel pathways that provide a model for understanding auditory projections from the IC through the MG and on to auditory cortex. A striking discovery about the tectothalamic circuit was identification of a substantial GABAergic component. Whether GABAergic projections match the parallel pathway organization has not been examined. We asked whether the parallel pathway concept is reflected in guinea pig tectothalamic pathways and to what degree GABAergic cells contribute to each pathway. We deposited retrograde tracers into individual MG subdivisions (ventral, MGv; medial, MGm; dorsal, MGd; suprageniculate, MGsg) to label tectothalamic cells and used immunochemistry to identify GABAergic cells. The MGv receives most of its IC input (\textasciitilde75%) from the IC central nucleus (ICc); MGd and MGsg receive most of their input (\textasciitilde70%) from IC dorsal cortex (ICd); and MGm receives substantial input from both ICc (\textasciitilde40%) and IC lateral cortex (\textasciitilde40%). Each MG subdivision receives additional input (up to 32%) from non-dominant IC subdivisions, suggesting cross-talk between the pathways. The proportion of GABAergic cells in each pathway depended on the MG subdivision. GABAergic cells formed \textasciitilde20% of IC inputs to MGv or MGm, \textasciitilde11% of inputs to MGd, and 4% of inputs to MGsg. Thus, non-GABAergic (i.e., glutamatergic) cells are most numerous in each pathway with GABAergic cells contributing to different extents. Despite smaller numbers of GABAergic cells, their distributions across IC subdivisions mimicked the parallel pathways. Projections outside the dominant pathways suggest opportunities for excitatory and inhibitory crosstalk. The results demonstrate parallel tectothalamic pathways in guinea pigs and suggest numerous opportunities for excitatory and inhibitory interactions within and between pathways.
Mellott Jeffrey G; Foster Nichole L; Ohl Andrew P; Schofield Brett R
Frontiers in neuroanatomy
2014
1905-07
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.3389/fnana.2014.00124" target="_blank" rel="noreferrer noopener">10.3389/fnana.2014.00124</a>
Ultrastructural characterization of GABAergic and excitatory synapses in the inferior colliculus.
auditory; inhibition; circuit; gamma-aminobutyric acid; ultrastructure
In the inferior colliculus (IC) cells integrate inhibitory input from the brainstem and excitatory input from both the brainstem and auditory cortex. In order to understand how these inputs are integrated by IC cells identification of their synaptic arrangements is required. We used electron microscopy to characterize GABAergic synapses in the dorsal cortex, central nucleus, and lateral cortex of the IC (ICd, ICc, and IClc) of guinea pigs. Throughout the IC, GABAergic synapses are characterized by pleomorphic vesicles and symmetric junctions. Comparisons of GABAergic synapses with excitatory synapses revealed differences (in some IC subdivisions) between the distributions of these synapse types onto IC cells. For excitatory cells in the IClc and ICd GABAergic synapses are biased toward the somas and large dendrites, whereas the excitatory boutons are biased toward spines and small dendrites. This arrangement could allow for strong inhibitory gating of excitatory inputs. Such differences in synaptic distributions were not observed in the ICc, where the two classes of bouton have similar distributions along the dendrites of excitatory cells. Interactions between excitatory and GABAergic inputs on the dendrites of excitatory ICc cells may be more restricted (i.e., reflecting local dendritic processing) than in the other IC subdivisions. Comparisons across IC subdivisions revealed evidence for two classes of GABAergic boutons, a small GABAergic (SG) class that is present throughout the IC and a large GABAergic (LG) class that is almost completely restricted to the ICc. In the ICc, LG, and SG boutons differ in their targets. SG boutons contact excitatory dendritic shafts most often, but also contact excitatory spines and somas (excitatory and GABAergic). LG synapses make comparatively fewer contacts on excitatory shafts, and make comparatively more contacts on excitatory spines and on somas (excitatory and GABAergic). LG boutons likely have a lemniscal origin.
Nakamoto Kyle T; Mellott Jeffrey G; Killius Jeanette; Storey-Workley Megan E; Sowick Colleen S; Schofield Brett R
Frontiers in neuroanatomy
2014
1905-07
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.3389/fnana.2014.00108" target="_blank" rel="noreferrer noopener">10.3389/fnana.2014.00108</a>
Subcollicular projections to the auditory thalamus and collateral projections to the inferior colliculus.
superior olive; medial geniculate nucleus; binaural; brain evolution; lateral lemniscus; paralemniscal area; parallel pathways; reticular formation
Experiments in several species have identified direct projections to the medial geniculate nucleus (MG) from cells in subcollicular auditory nuclei. Moreover, many cochlear nucleus cells that project to the MG send collateral projections to the inferior colliculus (IC) (Schofield et al., 2014). We conducted three experiments to characterize projections to the MG from the superior olivary and the lateral lemniscal regions in guinea pigs. For experiment 1, we made large injections of retrograde tracer into the MG. Labeled cells were most numerous in the superior paraolivary nucleus, ventral nucleus of the trapezoid body, lateral superior olivary nucleus, ventral nucleus of the lateral lemniscus, ventrolateral tegmental nucleus, paralemniscal region and sagulum. Additional sources include other periolivary nuclei and the medial superior olivary nucleus. The projections are bilateral with an ipsilateral dominance (66%). For experiment 2, we injected tracer into individual MG subdivisions. The results show that the subcollicular projections terminate primarily in the medial MG, with the dorsal MG a secondary target. The variety of projecting nuclei suggest a range of functions, including monaural and binaural aspects of hearing. These direct projections could provide the thalamus with some of the earliest (i.e., fastest) information regarding acoustic stimuli. For experiment 3, we made large injections of different retrograde tracers into one MG and the homolateral IC to identify cells that project to both targets. Such cells were numerous and distributed across many of the nuclei listed above, mostly ipsilateral to the injections. The prominence of the collateral projections suggests that the same information is delivered to both the IC and the MG, or perhaps that a common signal is being delivered as a preparatory indicator or temporal reference point. The results are discussed from functional and evolutionary perspectives.
Schofield Brett R; Mellott Jeffrey G; Motts Susan D
Frontiers in neuroanatomy
2014
1905-7
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.3389/fnana.2014.00070" target="_blank" rel="noreferrer noopener">10.3389/fnana.2014.00070</a>
Distribution of GABAergic cells in the inferior colliculus that project to the thalamus.
inhibition; auditory system; GAD; medial geniculate; tectothalamic
A GABAergic component has been identified in the projection from the inferior colliculus (IC) to the medial geniculate body (MG) in cats and rats. We sought to determine if this GABAergic pathway exists in guinea pig, a species widely used in auditory research. The guinea pig IC contains GABAergic cells, but their relative abundance in the IC and their relative contributions to tectothalamic projections are unknown. We identified GABAergic cells with immunochemistry for glutamic acid decarboxylase (GAD) and determined that \textasciitilde21% of IC neurons are GABAergic. We then combined retrograde tracing with GAD immunohistochemistry to identify the GABAergic tectothalamic projection. Large injections of Fast Blue, red fluorescent beads or FluoroGold were deposited to include all subdivisions of the MG. The results demonstrate a GABAergic pathway from each IC subdivision to the ipsilateral MG. GABAergic cells constitute \textasciitilde22% of this ipsilateral pathway. In addition, each subdivision of the IC had a GABAergic projection to the contralateral MG. Measured by number of tectothalamic cells, the contralateral projection is about 10% of the size of the ipsilateral projection. GABAergic cells constitute about 20% of the contralateral projection. In summary, the results demonstrate a tectothalamic projection in guinea pigs that originates in part from GABAergic cells that project ipsilaterally or contralaterally to the MG. The results show similarities to both rats and cats, and carry implications for the role of GABAergic tectothalamic projections vis-a-vis the presence (in cats) or near absence (in rats and guinea pigs) of GABAergic interneurons in the MG.
Mellott Jeffrey G; Foster Nichole L; Nakamoto Kyle T; Motts Susan D; Schofield Brett R
Frontiers in neuroanatomy
2014
1905-07
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.3389/fnana.2014.00017" target="_blank" rel="noreferrer noopener">10.3389/fnana.2014.00017</a>
Projections from the dorsal and ventral cochlear nuclei to the medial geniculate body.
thalamus; collateral projections; fear conditioning; lemniscal pathway; magnocellular pathway; multimodal processing; multipolar cells; T-stellate
Direct projections from the cochlear nucleus (CN) to the medial geniculate body (MG) mediate a high-speed transfer of acoustic information to the auditory thalamus. Anderson etal. (2006) used anterograde tracers to label the projection from the dorsal CN (DCN) to the MG in guinea pigs. We examined this pathway with retrograde tracers. The results confirm a pathway from the DCN, originating primarily from the deep layers. Labeled cells included a few giant cells and a larger number of small cells of unknown type. Many more labeled cells were present in the ventral CN (VCN). These cells, identifiable as multipolar (stellate) or small cells, were found throughout much of the VCN. Most of the labeled cells were located contralateral to the injection site. The CN to MG pathway bypasses the inferior colliculus (IC), where most ascending auditory information is processed. Anderson etal. (2006) hypothesized that CN-MG axons are collaterals of axons that reach the IC. We tested this hypothesis by injecting different fluorescent tracers into the MG and IC and examining the CN for double-labeled cells. After injections on the same side of the brain, double-labeled cells were found in the contralateral VCN and DCN. Most double-labeled cells were in the VCN, where they accounted for up to 37% of the cells labeled by the MG injection. We conclude that projections from the CN to the MG originate from the VCN and, less so, from the DCN. A significant proportion of the cells send a collateral projection to the IC. Presumably, the collateral projections send the same information to both the MG and the IC. The results suggest that T-stellate cells of the VCN are a major source of direct projections to the auditory thalamus.
Schofield Brett R; Motts Susan D; Mellott Jeffrey G; Foster Nichole L
Frontiers in neuroanatomy
2014
1905-07
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.3389/fnana.2014.00010" target="_blank" rel="noreferrer noopener">10.3389/fnana.2014.00010</a>
Perineuronal nets and GABAergic cells in the inferior colliculus of guinea pigs.
GABA; auditory; plasticity; extracellular matrix; inhibition; midbrain
Perineuronal nets (PNs) are aggregates of extracellular matrix that have been associated with neuronal plasticity, critical periods, fast-spiking cells and protection from oxidative stress. Although PNs have been reported in the auditory system in several species, there is disagreement about the distribution of PNs within the inferior colliculus (IC), an important auditory hub in the midbrain. Furthermore, PNs in many brain areas are preferentially associated with GABAergic cells, but whether such an association exists in the IC has not been addressed. We used Wisteria floribunda agglutinin staining and immunohistochemistry in guinea pigs to examine PNs within the IC. PNs are present in all IC subdivisions and are densest in the central portions of the IC. Throughout the IC, PNs are preferentially associated with GABAergic cells. Not all GABAergic cells are surrounded by PNs, so the presence of PNs can be used to subdivide IC GABAergic cells into "netted" and "non-netted" categories. Finally, PNs in the IC, like those in other brain areas, display molecular heterogeneity that suggests a multitude of functions.
Foster Nichole L; Mellott Jeffrey G; Schofield Brett R
Frontiers in neuroanatomy
2014
1905-07
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.3389/fnana.2013.00053" target="_blank" rel="noreferrer noopener">10.3389/fnana.2013.00053</a>
Ultrastructural examination of the corticocollicular pathway in the guinea pig: a study using electron microscopy, neural tracers, and GABA immunocytochemistry.
auditory cortex; bouton classification; corticofugal pathways; inferior colliculi; synaptic targets; ultrastructural variations
Projections from auditory cortex (AC) can alter the responses of cells in the inferior colliculus (IC) to sounds. Most IC cells show excitation and inhibition after stimulation of the AC. AC axons release glutamate and excite their targets, so inhibition is presumed to result from cortical activation of GABAergic IC cells that inhibit other IC cells via local projections. However, it is not known whether cortical axons contact GABAergic IC cells directly. We labeled corticocollicular axons by injecting fluorescent dextrans into the AC in guinea pigs. We visualized the tracer with diaminobenzidine and processed the tissue for electron microscopy. We identified presumptive GABAergic profiles with post-embedding anti-GABA immunogold histochemistry on ultrathin sections. We identified dextran-labeled cortical boutons in the IC and identified their postsynaptic targets according to morphology (e.g., spine, dendrite) and
Nakamoto Kyle T; Mellott Jeffrey G; Killius Jeanette; Storey-Workley Megan E; Sowick Colleen S; Schofield Brett R
Frontiers in neuroanatomy
2013
2013
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.3389/fnana.2013.00013" target="_blank" rel="noreferrer noopener">10.3389/fnana.2013.00013</a>
Cholinergic and non-cholinergic projections from the pedunculopontine and laterodorsal tegmental nuclei to the medial geniculate body in Guinea pigs.
GABA; auditory; thalamus; sleep; acetylcholine; arousal; glutamate
The midbrain tegmentum is the source of cholinergic innervation of the thalamus and has been associated with arousal and control of the sleep/wake cycle. In general, the innervation arises bilaterally from the pedunculopontine tegmental nucleus (PPT) and the laterodorsal tegmental nucleus (LDT). While this pattern has been observed for many thalamic nuclei, a projection from the LDT to the medial geniculate body (MG) has been questioned in some species. We combined retrograde tracing with immunohistochemistry for choline acetyltransferase (ChAT) to identify cholinergic projections from the brainstem to the MG in guinea pigs. Double-labeled cells (retrograde and immunoreactive for ChAT) were found in both the PPT (74%) and the LDT (26%). In both nuclei, double-labeled cells were more numerous on the ipsilateral side. About half of the retrogradely labeled cells were immunonegative, suggesting they are non-cholinergic. The distribution of these immunonegative cells was similar to that of the immunopositive ones: more were in the PPT than the LDT and more were on the ipsilateral than the contralateral side. The results indicate that both the PPT and the LDT project to the MG, and suggest that both cholinergic and non-cholinergic cells contribute substantially to these projections.
Motts Susan D; Schofield Brett R
Frontiers in neuroanatomy
2010
2010
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.3389/fnana.2010.00137" target="_blank" rel="noreferrer noopener">10.3389/fnana.2010.00137</a>
Circuitry underlying spectrotemporal integration in the auditory midbrain.
Female; Male; Time Factors; Animals; Acoustic Stimulation/*methods; Chiroptera; Auditory Pathways/*physiology; Mesencephalon/*physiology; Nerve Net/*physiology
Combination sensitivity in central auditory neurons is a form of spectrotemporal integration in which excitatory responses to sounds at one frequency are facilitated by sounds within a distinctly different frequency band. Combination-sensitive neurons respond selectively to acoustic elements of sonar echoes or social vocalizations. In mustached bats, this response property originates in high-frequency representations of the inferior colliculus (IC) and depends on low and high frequency-tuned glycinergic inputs. To identify the source of these inputs, we combined glycine immunohistochemistry with retrograde tract tracing. Tracers were deposited at high-frequency (\textgreater56 kHz), combination-sensitive recording sites in IC. Most glycine-immunopositive, retrogradely labeled cells were in ipsilateral ventral and intermediate nuclei of the lateral lemniscus (VNLL and INLL), with some double labeling in ipsilateral lateral and medial superior olivary nuclei (LSO and MSO). Generally, double-labeled cells were in expected high-frequency tonotopic areas, but some VNLL and INLL labeling appeared to be in low-frequency representations. To test whether these nuclei provide low frequency-tuned input to the high-frequency IC, we combined retrograde tracing from IC combination-sensitive sites with anterograde tracing from low frequency-tuned sites in the anteroventral cochlear nucleus (AVCN). Only VNLL and INLL contained retrogradely labeled cells near (
Yavuzoglu Asuman; Schofield Brett R; Wenstrup Jeffrey J
The Journal of neuroscience : the official journal of the Society for Neuroscience
2011
2011-10
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1523/JNEUROSCI.3529-11.2011" target="_blank" rel="noreferrer noopener">10.1523/JNEUROSCI.3529-11.2011</a>
Extracellular Molecular Markers and Soma Size of Inhibitory Neurons: Evidence for Four Subtypes of GABAergic Cells in the Inferior Colliculus.
Female; GABA; Male; Animals; auditory; Guinea Pigs; plasticity; Auditory Pathways/cytology/*physiology; Biomarkers; Cell Size; Extracellular Space/*physiology; gamma-Aminobutyric Acid/*physiology; Glutamate Decarboxylase/metabolism; Inferior Colliculi/cytology/*physiology; inhibition; Neuronal Plasticity/physiology; Neurons/*physiology/ultrastructure; perineuronal net; Vesicular Glutamate Transport Protein 2/metabolism; VGLUT2
UNLABELLED: Inhibition plays an important role in shaping responses to stimuli throughout the CNS, including in the inferior colliculus (IC), a major hub in both ascending and descending auditory pathways. Subdividing GABAergic cells has furthered the understanding of inhibition in many brain areas, most notably in the cerebral cortex. Here, we seek the same understanding of subcortical inhibitory cell types by combining staining for two types of extracellular markers–perineuronal nets (PNs) and perisomatic rings of terminals expressing vesicular glutamate transporter 2 (VGLUT2)–to subdivide IC GABAergic cells in adult guinea pigs. We found four distinct groups of GABAergic cells in the IC: (1) those with both a PN and a VGLUT2 ring; (2) those with only a PN; (3) those with only a VGLUT2 ring; and (4) those with neither marker. In addition, these four GABAergic subtypes differ in their soma size and distribution among IC subdivisions. Functionally, the presence or absence of VGLUT2 rings indicates differences in inputs, whereas the presence or absence of PNs indicates different potential for plasticity and temporal processing. We conclude that these markers distinguish four GABAergic subtypes that almost certainly serve different roles in the processing of auditory stimuli within the IC. SIGNIFICANCE STATEMENT: GABAergic inhibition plays a critical role throughout the brain. Identification of subclasses of GABAergic cells (up to 15 in the cerebral cortex) has furthered the understanding of GABAergic roles in circuit modulation. Inhibition is also prominent in the inferior colliculus, a subcortical hub in auditory pathways. Here, we use two extracellular markers to identify four distinct groups of GABAergic cells. Perineuronal nets and perisomatic rings of glutamatergic boutons are present in many subcortical areas and often are associated with inhibitory cells, but they have rarely been used to identify inhibitory subtypes. Our results further the understanding of inhibition in the inferior colliculus and suggest that these extracellular molecular markers may provide a key to distinguishing inhibitory subtypes in many subcortical areas.
Beebe Nichole L; Young Jesse W; Mellott Jeffrey G; Schofield Brett R
The Journal of neuroscience : the official journal of the Society for Neuroscience
2016
2016-04
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1523/JNEUROSCI.0217-16.2016" target="_blank" rel="noreferrer noopener">10.1523/JNEUROSCI.0217-16.2016</a>
Subtypes of GABAergic cells in the inferior colliculus.
Auditory system; Cell type; GABA; Inhibition; Perineuronal net
The inferior colliculus occupies a central position in ascending and descending auditory pathways. A substantial proportion of its neurons are GABAergic, and these neurons contribute to intracollicular circuits as well as to extrinsic projections to numerous targets. A variety of types of evidence - morphology, physiology, molecular markers - indicate that the GABAergic cells can be divided into at least four subtypes that serve different functions. However, there has yet to emerge a unified scheme for distinguishing these subtypes. The present review discusses these criteria and, where possible, relates the different properties. In contrast to GABAergic cells in cerebral cortex, where subtypes are much more thoroughly characterized, those in the inferior colliculus contribute substantially to numerous long range extrinsic projections. At present, the best characterized subtype is a GABAergic cell with a large soma, dense perisomatic synaptic inputs and a large axon that provides rapid auditory input to the thalamus. This large GABAergic subtype projects to additional targets, and other subtypes also project to the thalamus. The eventual characterization of these subtypes can be expected to reveal multiple functions of these inhibitory cells and the many circuits to which they contribute.
Schofield Brett R; Beebe Nichole L
Hearing research
2018
2018-10
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1016/j.heares.2018.10.001" target="_blank" rel="noreferrer noopener">10.1016/j.heares.2018.10.001</a>
Auditory cortical axons contact commissural cells throughout the guinea pig inferior colliculus.
AC; Animals; auditory cortex; Auditory Cortex/*physiology; Auditory Pathways/cytology; Axons/metabolism/*pathology; Brain Mapping; cortical layers; Fast Blue; FB; FD; Female; FG; Fluor0Ruby; fluorescein dextran; Fluorescence; FluoroGold; FR; G-; G+; GAD; GAD-immunonegative; GAD-immunopositive; GAD-neg; gamma-Aminobutyric Acid/metabolism; GB; Glutamate Decarboxylase/metabolism; glutamic acid decarboxylase; green RetroBeads; Guinea Pigs; I-VI; IC; IC central nucleus; IC dorsal cortex; IC lateral cortex; IC rostral cortex; ICc; ICd; IClc; ICrc; Inferior Colliculi/pathology/*physiology; inferior colliculus; Male; Mesencephalon/pathology; Microscopy; ps; pseudosylvian sulcus; rhinal sulcus; rs; white matter; wm
Projections from auditory cortex (AC) affect how cells in both inferior colliculi (IC) respond to acoustic stimuli. The large projection from the AC to the ipsilateral IC is usually credited with the effects in the ipsilateral IC. The circuitry underlying effects in the contralateral IC is less clear. The direct projection from the AC to the contralateral IC is relatively small. An unexplored possibility is that the large ipsilateral cortical projection contacts the substantial number of cells in the ipsilateral IC that project through the commissure to the contralateral IC. Apparent contacts between cortical boutons and commissural cells were identified in the left IC after injection of different fluorescent tracers into the left AC and the right IC. Commissural cells were labeled throughout the left IC, and many (23-34%) appeared to be contacted by cortical axons. In the central nucleus, both disc-shaped and stellate cells were contacted. Antibodies to glutamic acid decarboxylase (GAD) were used to identify GABAergic commissural cells. The majority (\textgreater86%) of labeled commissural cells were GAD-immunonegative. Despite low numbers of GAD-immunopositive commissural cells, some of these cells were contacted by cortical boutons. Nonetheless, most cortically contacted commissural cells were GAD-immunonegative (i.e., presumably glutamatergic). We conclude that auditory cortical axons contact primarily excitatory commissural cells in the ipsilateral IC that project to the contralateral IC. These corticocollicular contacts occur in each subdivision of the ipsilateral IC, suggesting involvement of commissural cells throughout the IC. This pathway - from AC to commissural cells in the ipsilateral IC - is a prime candidate for the excitatory effects of activation of the auditory cortex on responses in the contralateral IC. Overall this suggests that the auditory corticofugal pathway is integrated with midbrain commissural connections.
Nakamoto Kyle T; Sowick Colleen S; Schofield Brett R
Hearing research
2013
2013-12
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1016/j.heares.2013.10.003" target="_blank" rel="noreferrer noopener">10.1016/j.heares.2013.10.003</a>
Cholinergic cells of the pontomesencephalic tegmentum: connections with auditory structures from cochlear nucleus to cortex.
Acetylcholine/metabolism; Animals; Auditory Cortex/pathology; Auditory Pathways; Axons/physiology; Cholinergic Agents/*metabolism; Cholinergic Fibers/*metabolism; Cochlear Nucleus/*physiology; Cognition Disorders; Guinea Pigs; Humans; Neurotransmitter Agents/metabolism; Prosencephalon/pathology; Rats; Tegmentum Mesencephali/metabolism/*physiology
Acetylcholine (ACh) is a neuromodulator that is likely to play a role in plasticity as well as other phenomena at many sites in the auditory system. The auditory cortex receives cholinergic innervation from the basal forebrain, whereas the cochlea receives cholinergic innervation from the superior olivary complex. Much of the remainder of the auditory pathways receives innervation from the pedunculopontine and laterodorsal tegmental nuclei, two nuclei referred to collectively as the pontomesencephalic tegmentum (PMT). The PMT provides the major source of ACh to the auditory thalamus and the midbrain, and is a substantial source (in addition to the superior olivary complex) of ACh in the cochlear nucleus. Individual cholinergic cells in the PMT often have axon branches that innervate multiple auditory nuclei, including nuclei on both sides of the brain as well as nuclei at multiple levels of the auditory system. The auditory cortex has direct axonal projections to the PMT cells, including cholinergic cells that project to the inferior colliculus or cochlear nucleus. The divergent projections of PMT cholinergic cells suggest widespread effects on the auditory pathways. These effects are likely to include plasticity as well as novelty detection, sensory gating, reward behavior, arousal and attention. Descending projections from the forebrain, including the auditory cortex, are likely to provide a high level of cognitive input to these cholinergic effects. Dysfunction associated with the cholinergic system may play a role in disorders such as tinnitus and schizophrenia.
Schofield Brett R; Motts Susan D; Mellott Jeffrey G
Hearing research
2011
2011-09
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1016/j.heares.2010.12.019" target="_blank" rel="noreferrer noopener">10.1016/j.heares.2010.12.019</a>
Projections from auditory cortex contact ascending pathways that originate in the superior olive and inferior colliculus.
Animals; Auditory Cortex/*cytology; Auditory Pathways/*cytology; Fluorescence; Guinea Pigs; Inferior Colliculi/*cytology; Microscopy; Olivary Nucleus/*cytology; Staining and Labeling/methods
The superior olivary complex (SOC) and inferior colliculus (IC) are targets of cortical projections as well as sources of major ascending auditory pathways. This study examines whether the cortical projections contact cells in the SOC or IC that project to higher levels. First, we placed an anterograde tracer into the auditory cortex to label cortico-olivary axons and a retrograde tracer into the IC to label olivocollicular cells in guinea pigs. Cortical axons contacted many labeled cells in the ipsilateral SOC and fewer labeled cells in the contralateral SOC. Contacted cells projected to the ipsilateral or contralateral IC. In a second experiment, we labeled corticocollicular axons with an anterograde tracer and injected retrograde tracers into the medial geniculate (MG) to label colliculogeniculate cells. In the IC ipsilateral to the cortical injection, many cortical axons contacted colliculogeniculate cells in the dorsal cortex and external cortex of the IC. The contacted cells projected to the ipsilateral MG or, less often, to the contralateral MG. The results indicate that cortical projections are likely to contact cells in the SOC and IC that project to higher centers. This suggests that auditory cortex can modulate the ascending auditory pathways at multiple levels of the brainstem.
Peterson Diana Coomes; Schofield Brett R
Hearing research
2007
2007-10
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1016/j.heares.2007.06.009" target="_blank" rel="noreferrer noopener">10.1016/j.heares.2007.06.009</a>
Pathways from auditory cortex to the cochlear nucleus in guinea pigs.
Animals; Auditory Cortex/*anatomy & histology/physiology; Auditory Pathways/anatomy & histology/physiology; Axons/physiology/ultrastructure; Cochlear Nucleus/*anatomy & histology/physiology; Efferent Pathways/*anatomy & histology/physiology; Efferent/physiology; Fluorescence; Fluorescent Dyes; Guinea Pigs; Inferior Colliculi/*anatomy & histology/physiology; Microscopy; Neurons; Olivary Nucleus/*anatomy & histology/physiology
The inferior colliculus (IC) and superior olivary complex (SOC) are important sources of descending pathways to the cochlear nucleus. The IC and SOC are also targets of direct projections from the auditory cortex but it is not known if cortical axons contact the cells that project to the cochlear nucleus. Multi-labeling techniques were used to address this question in guinea pigs. A fluorescent anterograde tracer was injected into temporal cortex to label corticofugal axons. Different fluorescent tracers were injected into one or both cochlear nuclei to label olivary and collicular cells. The brain was subsequently processed for fluorescence microscopy and the IC and SOC were examined for apparent contacts between cortical axons and retrogradely labeled cells. The results suggest that cortical axons contact cochlear nucleus-projecting cells in both IC and SOC. In both regions, contacts were more numerous on the side ipsilateral to the injected cortex. In the IC, the contacted cells projected ipsilaterally or contralaterally to the CN. In the SOC, the contacted cells projected ipsilaterally, contralaterally or bilaterally to the CN. We conclude that auditory cortex is in a position to modulate descending pathways from both the IC and SOC to the cochlear nucleus.
Schofield Brett R; Coomes Diana L
Hearing research
2006
2006-07
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1016/j.heares.2006.01.004" target="_blank" rel="noreferrer noopener">10.1016/j.heares.2006.01.004</a>
Projections from auditory cortex to cholinergic cells in the midbrain tegmentum of guinea pigs.
Animals; Auditory Cortex/*metabolism; Auditory Pathways/metabolism; Axonal Transport; Axons/metabolism; Choline O-Acetyltransferase/*metabolism; Efferent Pathways/metabolism; Female; Fluorescent Antibody Technique; Guinea Pigs; Immunohistochemistry; Male; Neurons/*metabolism; Tegmentum Mesencephali/*metabolism
Anterograde and retrograde tracing techniques were used to characterize projections from the auditory cortex to the pedunculopontine and laterodorsal tegmental nuclei (PPT and LDT, respectively) in the midbrain tegmentum in guinea pigs. For anterograde tracing, tetramethylrhodamine dextran (FluoroRuby) was injected at several sites within auditory cortex. After sufficient time for transport, the brain was processed for immunohistochemistry with anti-choline acetyltransferase to reveal presumptive cholinergic cells. Anterogradely labeled axons were observed ipsilaterally and, in smaller numbers, contralaterally, in both the pedunculopontine and laterodorsal tegmental nuclei. In all four nuclei, tracer-labeled boutons appeared to contact immunolabeled (i.e., cholinergic) cells. The contacts occurred on cell bodies and dendrites. The results were similar following injections that spread across multiple auditory cortical areas or injections that were within primary auditory cortex. In order to confirm the anterograde results, in a second series of experiments, retrograde tracers were deposited in the pedunculopontine tegmental nucleus. These injections labeled layer V pyramidal cells in the auditory cortex. The results suggest an excitatory projection from primary auditory cortex bilaterally to cholinergic cells in the midbrain tegmentum. Such a pathway could allow auditory cortex to activate brainstem cholinergic circuits, possibly including the cholinergic pathways associated with arousal and gating of acoustic stimuli.
Schofield Brett R; Motts Susan D
Brain research bulletin
2009
2009-09
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1016/j.brainresbull.2009.06.015" target="_blank" rel="noreferrer noopener">10.1016/j.brainresbull.2009.06.015</a>
Cells in auditory cortex that project to the cochlear nucleus in guinea pigs.
Animals; Auditory Cortex/*cytology; Cochlear Nucleus/*cytology; Fluorescent Dyes; Guinea Pigs; Pyramidal Cells/*cytology
Fluorescent retrograde tracers were used to identify the cells in auditory cortex that project directly to the cochlear nucleus (CN). Following injection of a tracer into the CN, cells were labeled bilaterally in primary auditory cortex and the dorsocaudal auditory field as well as several surrounding fields. On both sides, the cells were limited to layer V. The size of labeled cell bodies varied considerably, suggesting that different cell types may project to the CN. Cells ranging from small to medium in size were present bilaterally, whereas the largest cells were labeled only ipsilaterally. In optimal cases, the extent of dendritic labeling was sufficient to identify the morphologic class. Many cells had an apical dendrite that could be traced to a terminal tuft in layer I. Such "tufted" pyramidal cells were identified both ipsilateral and contralateral to the injected CN. The results suggest that the direct pathway from auditory cortex to the cochlear nucleus is substantial and is likely to play a role in modulating the way the cochlear nucleus processes acoustic stimuli.
Schofield Brett R; Coomes Diana L; Schofield Ryan M
Journal of the Association for Research in Otolaryngology : JARO
2006
2006-06
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1007/s10162-005-0025-4" target="_blank" rel="noreferrer noopener">10.1007/s10162-005-0025-4</a>
GABAergic and non-GABAergic projections to the superior colliculus from the auditory brainstem.
Animals; Attention; Auditory Pathways/*physiology; Avoidance behavior; Brain Mapping; Escape; Female; Fluorescent Dyes/metabolism; Functional Laterality; GABAergic Neurons/*physiology; Glutamate Decarboxylase/*metabolism; Guinea Pigs; Inferior colliculus; Inhibition; Male; Nitric Oxide Synthase/metabolism; Nucleus of the brachium of the inferior colliculus; Orienting; Superior Colliculi/*cytology
The superior colliculus (SC) contains an auditory space map that is shaped by projections from several subcortical auditory nuclei. Both GABAergic (inhibitory) and excitatory cells contribute to these inputs, but there are contradictory reports regarding the sources of these inputs. We used retrograde tracing techniques in guinea pigs to identify cells in the auditory brainstem that project to the SC. We combined retrograde tracing with immunohistochemistry for glutamic acid decarboxylase (GAD) to identify putative GABAergic cells that participate in this pathway. Following a tracer injection in the SC, the nucleus of the brachium of the inferior colliculus (NBIC) contained the most labeled cells, followed by the inferior colliculus (IC). Smaller populations were observed in the sagulum, paralemniscal area, periolivary nuclei and ventrolateral tegmental nucleus. Overall, only 10% of the retrogradely labeled cells were GAD immunopositive. The presumptive inhibitory cells were observed in the NBIC, IC, superior paraolivary nucleus, sagulum and paralemniscal area. We conclude that the guinea pig SC receives input from a diverse set of auditory brainstem nuclei, some of which provide GABAergic input. These diverse origins of input to the SC likely represent a variety of functions. Inputs from the NBIC and IC likely provide spatial information for guiding orienting behaviors. Inputs from subcollicular nuclei are less likely to provide spatial information; rather, they may provide a shorter route for auditory information to reach the SC, and could generate avoidance or escape responses to an external threat.
Mellott Jeffrey G; Beebe Nichole L; Schofield Brett R
Brain structure & function
2018
2018-05
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1007/s00429-017-1599-4" target="_blank" rel="noreferrer noopener">10.1007/s00429-017-1599-4</a>
Anterograde Tract Tracing for Assaying Axonopathy and Transport Deficits in Glaucoma.
*Axonal transport; *Axonopathy; *Neuronal tracing; *Optic nerve; *Superior colliculus; Animal; Animals; Axonal Transport; Axons/metabolism/*pathology/physiology; Cholera Toxin/*metabolism; Confocal; Disease Models; Glaucoma/*diagnostic imaging/metabolism/physiopathology; Humans; Mice; Microscopy; Rats; Visual Pathways
Whether to stage degeneration or investigate early pathology in glaucoma, examination of axonal structure and function is essential. There are a wide variety of methods available to investigators using animal models of glaucoma, with varying utilities depending on the questions asked. Here, we describe the use of anterograde neuronal tract tracing using cholera toxin B (CTB) for the determination of axon transport integrity of the retinofugal projection. This method reveals the structure of the retinal axons as well as the functional integrity of anterograde transport systems.
Crish Samuel D; Schofield Brett R
Methods in molecular biology (Clifton, N.J.)
2018
1905-07
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1007/978-1-4939-7407-8_15" target="_blank" rel="noreferrer noopener">10.1007/978-1-4939-7407-8_15</a>
Bilateral projections to the thalamus from individual neurons in the inferior colliculus.
collateral; GABA; inferior colliculus; medial geniculate body; RRID:AB2278725; RRID:AB260754; synchronization
The medial geniculate body (MG) receives a large input from the ipsilateral inferior colliculus (IC) and a smaller but substantial input from the contralateral IC. Both crossed and uncrossed inputs comprise a large percentage of glutamatergic cells and a smaller percentage of GABAergic cells. We used double labeling with fluorescent retrograde tracers to identify individual IC cells that project bilaterally to the MGs in adult guinea pigs. We also used immunohistochemistry for glutamic acid decarboxylase to distinguish GABAergic from glutamatergic cells that project bilaterally to the MG. We found cells in the IC that contained both retrograde tracers, indicating that they project bilaterally. Across cases, the bilaterally projecting cells constituted up to 37% of the cells that project to the ipsilateral MG and up to 73% of the cells that project to the contralateral MG. GABAergic cells averaged 20% of the bilaterally-projecting population. We conclude that a population of IC cells sends branching axonal projections to innervate the MG bilaterally. Most of the neurons in this population are glutamatergic, with a minority that are GABAergic. A mixed projection, with glutamatergic cells outnumbering GABAergic cells, originates from each of the major IC subdivisions (central nucleus, dorsal cortex, and lateral cortex). The bilaterally projecting cells are likely to serve functions different from the larger unilateral projections, perhaps synchronizing activity on the two sides of the auditory brain.
Mellott Jeffrey G; Beebe Nichole L; Schofield Brett R
The Journal of comparative neurology
2019
2019-04
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1002/cne.24600" target="_blank" rel="noreferrer noopener">10.1002/cne.24600</a>
Perineuronal nets in subcortical auditory nuclei of four rodent species with differing hearing ranges.
guinea pig; inferior colliculus; mouse; naked mole-rat; plasticity; rat; RRID: AB141637; RRID: AB1500687; RRID: AB2336066; RRID: AB2336874; RRID: AB2336881; RRID: AB90460; superior olive; thalamus
Perineuronal nets (PNs) are aggregates of extracellular matrix molecules that surround some neurons in the brain. While PNs occur widely across many cortical areas, subcortical PNs are especially associated with motor and auditory systems. The auditory system has recently been suggested as an ideal model system for studying PNs and their functions. However, descriptions of PNs in subcortical auditory areas vary, and it is unclear whether the variation reflects species differences or differences in staining techniques. Here, we used two staining techniques (one lectin stain and one antibody stain) to examine PN distribution in the subcortical auditory system of four different species: guinea pigs (Cavia porcellus), mice (Mus musculus, CBA/CaJ strain), Long-Evans rats (Rattus norvegicus), and naked mole-rats (Heterocephalus glaber). We found that some auditory nuclei exhibit dramatic differences in PN distribution among species while other nuclei have consistent PN distributions. We also found that PNs exhibit molecular heterogeneity, and can stain with either marker individually or with both. PNs within a given nucleus can be heterogeneous or homogenous in their staining patterns. We compared PN staining across the frequency axes of tonotopically organized nuclei and among species with different hearing ranges. PNs were distributed non-uniformly across some nuclei, but only rarely did this appear related to the tonotopic axis. PNs were prominent in all four species; we found no systematic relationship between the hearing range and the number, staining patterns or distribution of PNs in the auditory nuclei.
Beebe Nichole L; Schofield Brett R
The Journal of comparative neurology
2018
2018-04
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1002/cne.24383" target="_blank" rel="noreferrer noopener">10.1002/cne.24383</a>
Persistence of intact retinal ganglion cell terminals after axonal transport loss in the DBA/2J mouse model of glaucoma.
*Axonal Transport/physiology; *bouton; *mitochondria; *neurodegeneration; *retinal; *RRID:IMSRJAX:000671; *RRID:IMSRJAX:007048; *RRID:SCR002716; *RRID:SCR002865; *superior colliculus; *synapse; Animal; Animals; Disease Models; Electron; Glaucoma/metabolism/*pathology; Imaging; Inbred DBA; Mice; Microscopy; Mitochondria/pathology; Neuroanatomical Tract-Tracing Techniques; Regression Analysis; Retinal Ganglion Cells/metabolism/*pathology; Scanning; Superior Colliculi/metabolism/*pathology; Synapses/metabolism/*pathology; Three-Dimensional; Visual Pathways/metabolism/pathology
Axonal transport defects are an early pathology occurring within the retinofugal projection of the DBA/2J mouse model of glaucoma. Retinal ganglion cell (RGC) axons and terminals are detectable after transport is affected, yet little is known about the condition of these structures. We examined the ultrastructure of the glaucomatous superior colliculus (SC) with three-dimensional serial block-face scanning electron microscopy to determine the distribution and morphology of retinal terminals in aged mice exhibiting varying levels of axonal transport integrity. After initial axonal transport failure, retinal terminal densities did not vary compared with either transport-intact or control tissue. Although retinal terminals lacked overt signs of neurodegeneration, transport-intact areas of glaucomatous SC exhibited larger retinal terminals and associated mitochondria. This likely indicates increased oxidative capacity and may be a compensatory response to the stressors that this projection is experiencing. Areas devoid of transported tracer label showed reduced mitochondrial volumes as well as decreased active zone number and surface area, suggesting that oxidative capacity and synapse strength are reduced as disease progresses but before degeneration of the synapse. Mitochondrial volume was a strong predictor of bouton size independent of pathology. These findings indicate that RGC axons retain connectivity after losing function early in the disease process, creating an important therapeutic opportunity for protection or restoration of vision in glaucoma. J. Comp. Neurol. 524:3503-3517, 2016. (c) 2016 Wiley Periodicals, Inc.
Smith Matthew A; Xia Christina Z; Dengler-Crish Christine M; Fening Kelly M; Inman Denise M; Schofield Brett R; Crish Samuel D
The Journal of comparative neurology
2016
2016-12
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1002/cne.24012" target="_blank" rel="noreferrer noopener">10.1002/cne.24012</a>
Retrograde axonal tracing with fluorescent markers.
*Fluorescent Dyes; Animals; Axons/*ultrastructure; Fluorescent Antibody Technique/*methods; Humans; Neural Pathways/*anatomy & histology
The growth of fluorescence imaging technology and the development of sensitive fluorescent retrograde tracers has provided many new approaches for analyzing neuronal circuits. Fluorescent markers provide unparalleled opportunity for combining axonal tract tracing with techniques such as immunohistochemistry or physiological recording. This unit describes the use of six different fluorescent tracers: Fast Blue, fluorescein dextran, FluoroGold, FluoroRuby, red beads, and green beads. Guidance is provided on how to choose a tracer for a particular experiment, and three methods are described for injecting the tracers, including pressure injection through a microsyringe or a micropipet, and iontophoretic injection through a micropipet. Criteria for selecting the most appropriate method are discussed. The protocols provide the information necessary to take advantage of the numerous fluorescent tracers that are available and to apply them to a wide variety of scientific questions.
Schofield Brett R
Current protocols in neuroscience
2008
2008-04
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1002/0471142301.ns0117s43" target="_blank" rel="noreferrer noopener">10.1002/0471142301.ns0117s43</a>