MULTIPLE MECHANISMS FOR PERIPHERAL ACTIVATION OF THE PEPTIDE-CONTAINING RADULA MECHANOAFFERENT NEURONS B21 AND B22 OF APLYSIA. Cropper, E. C., C. G. Evans, and S. C. Rosen. Department of Physiology and Biophysics, and the Fishberg Center for Research in Neurobiology, The Mt. Sinai Medical Center, One Gustave L. Levy Place, New York, NY 10029; 3Center for Neurobiology & Behavior, The New York State Psychiatric Institute, 722 W 168 Street, New York, NY 10032.
APStracts 3:0083N, 1996.
1) Recently a cluster of sensory neurons (peptidergic radula mechanoafferents) has been identified in the buccal ganglion of Aplysia that is likely to play an important role in influencing the activity of feeding motor programs. All of the neurons of this cluster, which includes the identified cells B21 and B22, send axons via the radula nerve to a layer of tissue that lies under the chitinous radula (the subradula tissue). 2) We show that the subradula tissue has contractile properties. In the absence of the central nervous system, contractions of the subradula tissue are elicited if the subradula tissue is stretched. Alternatively, contractions are elicited when extracellular suction electrodes are used to stimulate buccal nerve 3 or the radula nerve. 3) Previous studies have shown that neurons of the B21/B22 cluster respond to peripherally applied mechanical stimuli. We show that these neurons are also activated when the subradula tissue contracts. Axon spikes (A-spikes) can be intracellularly recorded from radula mechanoafferent neurons when contractions of the subradula tissue are elicited either by stretch, or by extracellular stimulation of buccal nerve 3. 4) Mechanical stimuli that are subthreshold when applied alone elicit A-spikes if they are applied while the subradula tissue is contracting. We postulate that this type of interaction may play an important role in gating sensory input to the feeding CPG.

Received 23 February 1996; accepted in final form 17 April 1996.
APS Manuscript Number J144-6.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 8 May 96