Suppressive control of the crustacean pyloric network by a pair of identified interneurons. II. Modulation of neuronal properties.

In the lobster Homarus, the 2 identified PS neurons have a strong suppressive modulatory effect on the activity of the pyloric network in the STG (Cazalets et al., 1990). In the present paper, we consider the effects of PS on individual pyloric neurons isolated from their partners in the network by cell photoinactivation and synaptic blockade. Three types of PS action are described: (1) a transient, EPSP-mediated depolarization of the PD, VD, and AB neurons; (2) a long-lasting hyperpolarization concomitant with a loss of oscillatory properties in the PD and LP neurons; (3) a long-lasting depolarization without modification of oscillatory properties in the PY and IC neurons. The various effects of PS on isolated pyloric cells were consistent with the overall effects of PS on the intact pyloric network.