Contribution of NMDA and AMPA receptors to temporal patterning of auditory responses in the inferior colliculus.
Animals; Chiroptera/*physiology; Neurons/physiology; Action Potentials/drug effects; Excitatory Amino Acid Antagonists/pharmacology; Quinoxalines/pharmacology; Inferior Colliculi/cytology/drug effects/*physiology; Piperazines/pharmacology; *Acoustic Stimulation; Reaction Time/drug effects/*physiology; N-Methyl-D-Aspartate/*physiology; Receptors; AMPA/*physiology
Although NMDA receptors (NMDARs) are associated with synaptic plasticity, they form an essential part of responses to sensory stimuli. We compared contributions of glutamatergic NMDARs and AMPA receptors (AMPARs) to auditory responses in the inferior colliculus (IC) of awake, adult mustached bats. We examined the magnitude and temporal pattern of responses to tonal signals in single units before, during, and after local micro-iontophoretic application of selective antagonists to AMPARs [NBQX (1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide)] and NMDARs [CPP ((+/-)3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid)]. Combined blockade of AMPARs and NMDARs eliminated excitatory responses in nearly all neurons, whereas separate blockade of each receptor was quantitatively similar, causing substantial (\textgreater 50%) spike reductions in approximately 75% of units. The major result was that effects of receptor blockade were most closely related to the first-spike latency of a unit. Thus, AMPAR blockade substantially reduced spikes in all short-latency units (\textless 12 ms) but never in long-latency units (\textgreater or = 12 ms). NMDAR blockade had variable effects on short-latency units but reduced spikes substantially for all long-latency units. There were no distinct contributions of AMPARs and NMDARs to early and late elements of responses. Thus, AMPAR blockade reduced early (onset) spikes somewhat more effectively than NMDAR blockade in short-latency units, but NMDAR blockade reduced onset spikes more effectively in long-latency units. AMPAR and NMDAR blockade were equally effective in reducing later elements of sustained responses in short-latency units, whereas NMDAR blockade was much more effective in long-latency units. These results indicate that NMDARs play multiple roles for signal processing in adult IC neurons.
Sanchez Jason Tait; Gans Donald; Wenstrup Jeffrey J
The Journal of neuroscience : the official journal of the Society for Neuroscience
2007
2007-02
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.2894-06.2007" target="_blank" rel="noreferrer noopener">10.1523/JNEUROSCI.2894-06.2007</a>
Responses in the inferior colliculus of the guinea pig to concurrent harmonic series and the effect of inactivation of descending controls.
*Acoustic Stimulation; Action Potentials/physiology; Animal; Animals; Auditory Cortex/*physiology; Auditory Pathways/*physiology; Female; Guinea Pigs; Inferior Colliculi/*physiology; Male; Models; Pitch Perception/physiology
One of the fundamental questions of auditory research is how sounds are segregated because, in natural environments, multiple sounds tend to occur at the same time. Concurrent sounds, such as two talkers, physically add together and arrive at the ear as a single input sound wave. The auditory system easily segregates this input into a coherent perception of each of the multiple sources. A common feature of speech and communication calls is their harmonic structure and in this report we used two harmonic complexes to study the role of the corticofugal pathway in the processing of concurrent sounds. We demonstrate that, in the inferior colliculus (IC) of the anesthetized guinea pig, deactivation of the auditory cortex altered the temporal and/or the spike response to the concurrent, monaural harmonic complexes. More specifically, deactivating the auditory cortex altered the representation of the relative level of the complexes. This suggests that the auditory cortex modulates the representation of the level of two harmonic complexes in the IC. Since sound level is a cue used in the segregation of auditory input, the corticofugal pathway may play a role in this segregation.
Nakamoto Kyle T; Shackleton Trevor M; Palmer Alan R
Journal of neurophysiology
2010
2010-04
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/10.1152/jn.00451.2009" target="_blank" rel="noreferrer noopener">10.1152/jn.00451.2009</a>