RAPID COMMUNICATION Dopaminergic Modulation of Inhibitory Glutamate Receptors in the Lobster Stomatogastric Ganglion

Cleland, Thomas A. and Allen I. Selverston. Dopaminergic modto iontophoretically applied glutamate in situ, presumably ulation of inhibitory glutamate receptors in the lobster stomatogasmediated solely by ‘‘postsynaptic’’ input resistance and tric ganglion. J. Neurophysiol. 78: 3450–3452, 1997. The intrinsic IGluR modulation, are also diverse and specific to particular rhythmicity of the spiny lobster stomatogastric ganglion (STG) is identified cells (Johnson and Harris-Warrick 1997). In a strongly influenced by the strengths of the graded synapses between sample of isolated, voltage-clamped STG neurons in culture, identified cells within the neural network. These synaptic strengths however, in which membrane currents can be directly meacan be powerfully influenced by chemical neuromodulators such sured, dopamine consistently suppressed IGluR currents. To as dopamine and serotonin. Most of the intraganglionic chemical the extent that this IGluR response is representative of postsynapses in the STG are mediated by postsynaptic inhibitory glutasynaptic glutamate receptors in situ, direct modulation of mate receptors (IGluRs). To determine whether or not direct effects on these IGluRs contribute to the modulation of synaptic IGluRs is clearly only one component of a complex suite of strength, unidentified STG neurons were extracted into primary preand postsynaptic effector mechanisms influencing net culture and the effects of these aminergic neuromodulators on the synaptic strength. The effects of serotonin on synaptic glutamate-evoked membrane current were assessed. Dopamine strengths in the STG, in contrast, may not involve direct (100 mM) reliably and significantly reduced the whole cell slope IGluR modulation. Some of these data were previously pubconductance of all IGluRs tested. Serotonin (20 mM) never affected lished in abstract form (Cleland and Selverston 1996). the IGlu response, although it clearly altered other cellular mem-