APStracts 4:222N, 1997.

Dopaminergic modulation of inhibitory glutamate receptors in the lobster stomatogastric ganglion. Thomas A. Cleland and Allen I. Selverston. Biology Department, 0357, University of California, San Diego, La Jolla, CA 92093-0357.

APStracts 4:222N, 1997.

ABSTRACT
The intrinsic rhythmicity of the spiny lobster stomatogastric ganglion (STG) is strongly influenced by the strengths of the graded synapses between identified cells within the neural network. These synaptic strengths can be powerfully influenced by chemical neuromodulators such as dopamine and serotonin. Most of the intraganglionic chemical synapses in the STG are mediated by postsynaptic inhibitory glutamate receptors (IGluRs). In order to determine whether direct effects on these IGluRs contribute to the modulation of synaptic strength, unidentified STG neurons were extracted into primary culture, and the effects of these aminergic neuromodulators on the glutamate- evoked membrane current were assessed. Dopamine (100 M) reliably and significantly reduced the whole-cell slope conductance of all IGluRs tested. Serotonin (20 M) never affected the IGlu response, although it clearly altered other cellular membrane properties. While all identified STG neurons may not conform to these observations, the data reveal a specific dopamine- activated modulatory pathway within cultured neurons which reduces IGluR slope conductance. The relationship between IGluR modulation and net synaptic modulation in situ contributes to an emerging model in which synaptic strengths can be multiply modulated at different functional sites, yielding a complex, distributed, and state-dependent regulatory structure.

Received 21 January 1997; accepted in final form 2 September 1997.
APS Manuscript Number J40-7.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 5 September 1997