Neurons in the buccal ganglia of Navanax inermis which control circumferential muscles of the pharynx showed typical electrotonic coupling when there was little synoptic activity in them. When there was much inhibitory activity, the effective sign of coupling was reversed; that is, hyperpolaritation and depolarization of one cell caused depolarization and hyperpolarization of the others. A neural circuit explaining these results involves inhibitory neurons etectrotonically coupled to and also inhibitory to the circumferential neurons that are themselves coupled. This circuit offers considerable flexibility for mediation of different activity patterns in this simple neuronal system.
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