Projections from auditory cortex to midbrain cholinergic neurons that project to the inferior colliculus.
Acetylcholine/*metabolism; Amidines; Animals; Auditory Cortex/*cytology/metabolism; Auditory Perception/physiology; Brain Mapping; Choline O-Acetyltransferase/metabolism; Cholinergic Fibers/metabolism/ultrastructure; Dextrans; Female; Functional Laterality/physiology; Guinea Pigs; Immunohistochemistry; Inferior Colliculi/*cytology/metabolism; Male; Mesencephalon/*cytology/metabolism; Neural Pathways/cytology/metabolism; Neuroanatomical Tract-Tracing Techniques; Neuronal Tract-Tracers; Neurons/*cytology/metabolism; Pedunculopontine Tegmental Nucleus/*cytology/metabolism; Rhodamines; Synaptic Transmission/physiology
We have shown that auditory cortex projects to cholinergic cells in the pedunculopontine tegmental nucleus (PPT) and laterodorsal tegmental nucleus (LDT). PPT and LDT are the sources of cholinergic projections to the inferior colliculus, but it is not known if the cortical inputs contact the cholinergic cells that project to the inferior colliculus. We injected FluoroRuby into auditory cortex in pigmented guinea pigs to label cortical projections to PPT and LDT. In the same animals, we injected Fast Blue into the left or right inferior colliculus to label PPT and LDT cells that project to the inferior colliculus. We processed the brain to identify cholinergic cells with an antibody to choline acetyltransferase, which was visualized with a green fluorescent marker distinguishable from both FluoroRuby and Fast Blue. We then examined the PPT and LDT to determine whether boutons of FluoroRuby-labeled cortical axons were in close contact with cells that were double-labeled with the retrograde tracer and the immunolabel. Apparent contacts were observed ipsilateral and, less often, contralateral to the injected cortex. On both sides, the contacts were more numerous in PPT than in LDT. The results indicate that auditory cortex projects directly to brainstem cholinergic cells that innervate the ipsilateral or contralateral inferior colliculus. This suggests that cortical projections could elicit cholinergic effects on both sides of the auditory midbrain.
Schofield B R
Neuroscience
2010
2010-03
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1016/j.neuroscience.2009.12.008" target="_blank" rel="noreferrer noopener">10.1016/j.neuroscience.2009.12.008</a>
Projection to the inferior colliculus from the basal nucleus of the amygdala.
Animals; Acoustic Stimulation/methods; Species Specificity; Action Potentials/physiology; Amygdala/*cytology/physiology; Dextrans; Rhodamines; Fluorescent Dyes; *Stilbamidines; Auditory Cortex/cytology; Auditory Pathways/*cytology/physiology; Axonal Transport/physiology; Brain Stem/cytology; Chiroptera/*anatomy & histology/physiology; Cholera Toxin/pharmacokinetics; Inferior Colliculi/*cytology/physiology; Neurons/cytology/physiology; Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate; Electrodes; Implanted
This report describes a projection from the amygdala, a forebrain center mediating emotional expression, to the inferior colliculus (IC), the midbrain integration center of the ascending auditory system. In the IC of mustached bats (Pteronotus parnellii) and pallid bats (Antrozous pallidus), we placed deposits of retrograde tracers at physiologically defined sites and then searched for retrogradely labeled somata in the forebrain. Labeling was most sensitive in experiments using cholera toxin B-subunit as tracer. We consistently observed retrograde labeling in a single amygdalar subdivision, the magnocellular subdivision of the basal nucleus (Bmg). The Bmg is distinctive across mammals, containing the largest cells in the amygdala and the most intense acetylcholinesterase staining. Labeled amygdalar cells occurred ipsilateral and contralateral to IC deposits, but ipsilateral labeling was greater, averaging 72%. Amygdalar labeling was observed after tracer deposits throughout the IC, including its central nucleus (ICC). In comparison, labeling in the auditory cortex (layer V) was heavily ipsilateral (averaging 92%). Cortical labeling depended on the location of IC deposits: dorsomedial deposits resulted in the most labeled cells, whereas ventrolateral deposits labeled few or no cortical cells. Cortical labeling occurred after several deposits in the ICC. Across experiments, the average number of labeled cells in the amygdala was similar to that in the auditory cortex, indicating that the amygdalocollicular projection is significant. The results demonstrate a direct, widespread projection from the basal amygdala to the IC. They also suggest the presence of a rapid thalamoamygdalocollicular feedback circuit that may impose emotional content onto processing of sensory stimuli at a relatively low level of an ascending sensory pathway.
Marsh Robert A; Fuzessery Zoltan M; Grose Carol D; Wenstrup Jeffrey J
The Journal of neuroscience : the official journal of the Society for Neuroscience
2002
2002-12
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/10.1523/jneurosci.22-23-10449.2002" target="_blank" rel="noreferrer noopener">10.1523/jneurosci.22-23-10449.2002</a>