Amine Modulation of Glutamate Responses from Pyloric Motor Neurons in the Lobster Stomatogastric Ganglion. Bruce R. Johnson and Ronald M. Harris-Warrick. Section of Neurobiology and Behavior, S.G. Mudd Hall, Cornell University Ithaca, NY 14853.
APStracts 4:223N, 1997.
ABSTRACT
The amines dopamine (DA), serotonin (5HT) and octopamine (Oct) each elicit a distinctive motor pattern from a quiescent pyloric network in the lobster stomatogastric ganglion (STG). We have previously demonstrated that these amines alter the synaptic strength at multiple, distributed sites within the pyloric network, which could contribute to the amine-induced motor patterns. Here, we examined the post-synaptic contribution to these changes in synaptic strength by determining how the amines modify responses of pyloric motor neurons to glutamate (Glu), one of the network transmitters, applied iontophoretically into the STG neuropil. Dopamine reduced the Glu responses of the pyloric dilator (PD), ventricular dilator (VD) and inferior cardiac (IC) neurons and enhanced the Glu responses of the lateral pyloric (LP) and pyloric constrictor (PY) neurons. The only effect of 5HT was to reduce the Glu response of the VD neuron. Octopamine enhanced the Glu responses of the LP and PY neurons but did not affect the PD, VD and IC responses. We also examined amine effects on the depolarizing responses to iontophoresed acetylcholine (ACh) in the PD and VD and found that they paralleled the amine effects on Glu responses in these neurons. This suggests that amine modulation of PD and VD responses to Glu and ACh may be explained by general changes in the ionic conductance of these neurons. We compare our results with our earlier work describing amine effects on synaptic strength and input resistance to show that amines act at both pre- and post-synaptic sites to modify graded synaptic transmission in the pyloric network. 

Received 5 May 1997; accepted in final form 2 September 1997.
APS Manuscript Number J363-7.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 5 September 1997