Structure of the Network Mediating Siphon-Elicited Siphon Withdrawal in Aplysia. Frost, William N., and Eric R. Kandel. Howard Hughes Medical Institute, New York, New York 10032 and Center for Neurobiology and Behavior, Columbia University College of Physicians and Surgeons, New York State Psychiatric Institute, Department of Neurobiology and Anatomy, University of Texas Medical School, P.O. Box 20708, Houston, TX 77225.
APStracts 2:0008N, 1995.
SUMMARY AND CONCLUSIONS
1. The network mediating siphon-elicited siphon withdrawal in Aplysia is a useful model system for cellular studies of simple forms of learning and memory. Here we describe 3 new cells in this circuit, L33, L34 and L35, and several new connections amongst the following network neurons: LE, L16, L29, L30, L32, L33, L34, L35. Based on these findings, we present an updated diagram of the network. Altogether, 100 neurons have now been identified in the abdominal ganglion which can participate in both siphon-elicited and spontaneous respiratory pumping siphon withdrawals. 2. Two features of the interneuronal population may have important behavioral functions. First, the L29 interneurons make fast and slow excitatory connections onto the LFS cells, which may be important for transforming brief sensory neuron discharges into the long lasting motor neuron firing which underlies withdrawal duration. Second, inhibitory interneurons are prominent in the network. The specific connectivity of certain of these interneurons is appropriate to block potentially interfering inhibitory inputs from other networks during execution of the behavior. 3. Deliberate searches have so far revealed very few excitatory interneuronal inputs to the network interneurons and motor neurons within the abdominal ganglion. These results, together with intracellular studies by others, are more consistent at present with a relatively dedicated, rather than a highly distributed organizational scheme for the siphon-elicited siphon withdrawal circuitry.

Received 10 February; accepted in final form 8 February 1995.
APS Manuscript Number J68-4.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on  3 April 1995.