The Journal of Neuroscience, 2001, 21:RC124:1-6
RAPID COMMUNICATION
Spectral Integration in the Inferior Colliculus: Role of
Glycinergic Inhibition in Response Facilitation
Jeffrey J.
Wenstrup and
Scott A.
Leroy
Department of Neurobiology and Pharmacology, Northeastern Ohio
Universities College of Medicine, Rootstown, Ohio 44272
This study examined the contribution of glycinergic inhibition to
the time-sensitive spectral integration performed by neurons in the
inferior colliculus of the mustached bat (Pteronotus
parnellii). These neurons are sometimes called
combination-sensitive because they display facilitatory (or inhibitory)
responses to the combination of distinct spectral elements in sonar or
social vocalizations. Present in a wide range of vertebrates,
their temporally and spectrally selective integration is thought to
endow them with the ability to discriminate among social vocalizations
or to analyze particular cues concerning sonar targets. The mechanisms
that underlie these responses or the sites in the auditory system where
they are created are not known.
We examined combination-sensitive neurons that are facilitated by the
presentation of two different harmonic elements of the bat's sonar
call and echo. Responses of 24 single units were recorded before and
during local application of strychnine, an antagonist of glycinergic
inhibition. For each of the 24 units, strychnine application
eliminated or greatly reduced temporally sensitive facilitation. There
was no difference in this effect for neurons tuned to frequencies
associated with the frequency-modulated or the constant-frequency sonar components.
These results are unusual because glycine is considered to be an
inhibitory neurotransmitter, but here it appears to be essential for
the expression of combination-sensitive facilitation. The findings
provide strong evidence that facilitatory combination-sensitive response properties present throughout the mustached bat's auditory midbrain, thalamus, and cortex originate through neural interactions in
the inferior colliculus.
Key words:
auditory pathways; bat; combination-sensitive; complex
sounds; frequency integration; glycine; inferior colliculus; mustached
bat; spectral integration; strychnine
Copyright © Society for Neuroscience 0270-6474//$05.00/0
Previous Article | Next Article
