Organization of the stomatogastric ganglion of the spiny lobster

SummaryThe Stomatogastric ganglion ofPanulirus interruptus contains about 30 neurons, and controls the movements of the lobster's stomach. When experimentally isolated, the ganglion continues to generate complex rhythmic patterns of activity in its motor neurons which are similar to those seen in intact animals.In this paper, we describe the synaptic organization of a group of six neurons which drive the stomach's lateral teeth (Figs. 2, 6). This group includes four motor neurons and two interneurons, all but one of which were recorded and stimulated with intracellular microelectrodes.One pair of synergistic motor neurons, LGN and MGN, are electrotonically coupled and reciprocally inhibitory (Figs. 9, 12). A second pair of synergistic motor neurons, the LPGNs, are antagonists of LGN and MGN. The LPGNs are electrotonically coupled (Fig. 14), and are both inhibited by LGN and MGN (Figs. 8, 11). The LPGNs inhibit MGN (Fig. 15) but not LGN. One of the two interneurons in the ganglion, Int 1, reciprocally inhibits both LGN and MGN (Figs. 10, 13). The other interneuron, Int 2, excites Int 1 and inhibits the LPGNs (Fig. 16). The synaptic connections observed in the ganglion are reflected in the spontaneous activity recorded from the isolated ganglion and from intact animals.From the known synaptic organization and observations on the physiological properties of each of the neurons, we have formulated some hypotheses about the pattern-generating mechanism. We found no evidence that any of the neurons are endogenous bursters.