Synaptic interactions in the cardiac ganglion of the spiny lobsterPanulirus interruptus

Summary

Synaptic interactions between neurons of the spiny lobster (Panulirus interruptus) cardiac ganglion have been investigated. All four small cells make synaptic contacts with all large cells (Fig. 1). The anterior four large cells all respond with similar synaptic depolarizations in response to a small cell impulse as follows: to cell 6–16.4 mV; to cell 7-3.1 mV; to cell 8-1.9 mV; and to cell 9-1.3 mV (Fig. 2). The average synaptic potentials measured in the soma of cell 5 are smaller: to cell 6-2.5 mV; to cell 7-1.5 mV; to cell 8-1.0 mV; and to cell 9-0.7 mV. Cell 1-4 PSP's due to cell 6 impulses antifacilitate strongly, while those from cells 7, 8 and 9 antifacilitate only weakly if at all. PSP's in cell 5 show neither facilitation nor antifacilitation. Cell 6 receives spike mediated input from some small cells (Fig. 7). Synaptic connections between cells 8 and 9 if they exist at all, are very weak (Fig. 6). The most important interactions between cells 8 and 9 are probably via electrotonic connections.