Regulation of Synaptic Depression Rates in the Cricket Cercal Sensory
System.
Andrew A.V. Hill and Ping Jin.
Biology Department, University of Massachusetts, Amherst MA 01003.
APStracts 4:352N, 1997.
ABSTRACT
In order to assess the roles of pre- and postsynaptic mechanisms in the
regulation of depression, short-term synaptic depression was characterized at
the synapses between sensory neurons and two interneurons in the cricket
cercal sensory system. Changes in EPSP amplitude with repetitive stimulation
at 5 and 20 Hz were quantified and fitted to the depletion model of
transmitter release. The depression rates of different sensory neuron synapses
on a single interneuron varied with the age of the sensory neurons such that
old sensory neuron synapses depressed faster than young synapses. While all
synapses showed depression, short-term facilitation was selectively expressed
only at sensory neuron synapses on one interneuron, the medial giant
interneuron (MGI). These synapses showed concurrent facilitation and
depression with high frequency stimulation (100Hz) whereas the synapses on
another interneuron, 10-3, showed only depression at all stimulus frequencies.
A previous study showed that the ability of a synapse to facilitate is
correlated with the identity of the postsynaptic neuron. The present results
indicate that depression and facilitation are regulated independently;
depression is regulated presynaptically in a manner related to sensory neuron
age whereas facilitation is regulated by the postsynaptic target.
Received 2 May 1997; accepted in final form 1 December 1997.
APS Manuscript Number J352-7.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 12 December 1997