Amine modulation of glutamate responses from pyloric motor neurons in lobster stomatogastric ganglion

Johnson, Bruce R. and Ronald M. Harris-Warrick. Amine mod- central pattern generator (CPG) of the lobster stomatogastric ulation of glutamate responses from pyloric motor neurons in lob- ganglion (STG), to better understand how synaptic rewiring ster stomatogastric ganglion. J. Neurophysiol. 78: 3210–3221, contributes to network flexibility. The pyloric CPG generates 1997. The amines dopamine (DA), serotonin (5-HT), and octo- rhythmic foregut movements responsible for filtering foodpamine (Oct) each elicit a distinctive motor pattern from a quies- particles and for gastric fluid circulation (Johnson and cent pyloric network in the lobster stomatogastric ganglion (STG). Hooper 1992). In the spiny lobster, Panulirus interruptus,We previously have demonstrated that these amines alter the synap-the synaptic connectivity between the six major cell types oftic strength at multiple, distributed sites within the pyloric network this 14-neuron network is known completely (Miller 1987;that could contribute to the amine-induced motor patterns. Here, Mulloney 1987) and includes graded and spike-evoked in-we examined the postsynaptic contribution to these changes in synaptic strength by determining how the amines modify responses hibitory chemical synapses as well as both rectifying and of pyloric motor neurons to glutamate (Glu), one of the network nonrectifying electrical synapses (Hartline and Graubard transmitters, applied iontophoretically into the STG neuropil. Do- 1992; Hartline et al. 1988; Johnson et al. 1993a). pamine reduced the Glu responses of the pyloric dilator (PD), We have examined the ability of the amines dopamine ventricular dilator (VD), and inferior cardiac (IC) neurons and (DA), serotonin (5-HT), and octopamine (Oct) to induce enhanced the Glu responses of the lateral pyloric (LP) and pyloric plasticity at synapses within the pyloric network. These constrictor (PY) neurons. The only effect of 5-HT was to reduce amines are endogenous modulators in Crustacea (Fingermanthe Glu response of the VD neuron. Oct enhanced the Glu response