Department of Anesthesiology

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Frequency-dependent regulation of afferent transmission in the feeding circuitry of Aplysia.

TitleFrequency-dependent regulation of afferent transmission in the feeding circuitry of Aplysia.
Publication TypeJournal Article
Year of Publication2003
AuthorsEvans CG, Jing J, Proekt A, Rosen SC, Cropper EC
JournalJ Neurophysiol
Volume90
Issue6
Pagination3967-77
Date Published2003 Dec
ISSN0022-3077
KeywordsAnimals, Aplysia, Cheek, Electric Stimulation, Electrophysiology, Feeding Behavior, Functional Laterality, Kinetics, Mechanoreceptors, Motor Neurons, Neurons, Afferent, Patch-Clamp Techniques, Synaptic Transmission
Abstract

During rhythmic behaviors, sensori-motor transmission is often regulated so that there are phasic changes in afferent input to follower neurons. We study this type of regulation in the feeding circuit of Aplysia. We characterize effects of the B4/5 interneurons on transmission from the mechanoafferent B21 to the radula closer motor neuron B8. In quiescent preparations, B4/5-induced postsynaptic potentials (PSPs) can block spike propagation in the lateral process of B21 and inhibit afferent transmission. B4/5 are, however, active during the retraction phase of motor programs, i.e., when mechanoafferent transmission to B8 presumably occurs. To determine whether mechanoafferent transmission is necessarily inhibited when B4/5 are active, we characterize the B4/5 firing frequency during retraction and show that, for the most part, it is low (below 15 Hz). There is, therefore, a low probability that spike propagation will be inhibited. The relative ineffectiveness of low frequency activity is not simply a consequence of insufficient PSP magnitude, because a single PSP can block spike propagation. Instead, it is related to the fact that PSPs have a short duration. When B4/5 fire at a low frequency, there is therefore a low probability that afferent transmission in the lateral process of B21 can be inhibited. In conclusion, we demonstrate that afferent transmission will not always be affected when a neuron that exerts inhibitory effects is active. Although a cell may be ineffective when it fires at a low frequency, ineffectiveness is not necessarily a consequence of spike frequency per se. Instead it may be due to spike timing.

DOI10.1152/jn.00786.2003
Alternate JournalJ. Neurophysiol.
PubMed ID14507990
Grant ListK02 MH-01267 / MH / NIMH NIH HHS / United States
MH-35564 / MH / NIMH NIH HHS / United States
MH-51393 / MH / NIMH NIH HHS / United States
RR-10294 / RR / NCRR NIH HHS / United States