The burst activity of different cell regions and intercellular co-ordination in the cardiac ganglion of the crab, Eriocheir japonicus.

The crustacean cardiac ganglion, which is an autonomous nervous system producing regular periodic burst discharges, is a useful preparation for experiments on spontaneity and integrative interaction among neurones. The neurophysiology of the ganglion has been studied by many investigators (for references see Hagiwara, 1961; Bullock & Horridge, 1965). In the lobster intracellular studies have been made on burst initiation, synchronous activity and intercellular co-ordination. Synaptic and electrotonic interactions are important for burst formation among ganglion cells. The burst is initiated in the pacemaker small cell, which fires repeatedly (Hagiwara & Bullock, 1957; Hartline, 1967). Recently, it was found that two small cells among four are pacemakers which control activities of large cells (or followers) through synaptic interactions; one of the two, which is the primary pacemaker, induces repetitive small synaptic potentials, increasing the excitability of large cells (Tazaki, 1971A). In a stomatopod, Squilla, the slow potential has been demonstrated to be a pacemaker potential for periodic burst discharge (Watanabe, Obara & Akiyama, 1967). In the crab intracellular studies on pacemaker cells have been made (Bullock & Terzuolo, 1957), and some characteristics of the pacemaker slow potential for repetitive spike generation have been reported (Tazaki, 1970, 1971a). Synaptic interaction among neurones in the crab has not, however, been studied in detail. The present experiment is concerned with burst activity and cellular interaction in the crab cardiac ganglion. Electrical activity was recorded intracellularly from the soma and axon of a ganglion cell. In this material the neuronal activities of different cell regions could be simultaneously observed because soma and axon were impaled with little difficulty. Synaptic interactions mediated by impulses were examined among ganglion cells located in the anterior and posterior parts. The attempt was made to compare the present results with those obtained from cardiac ganglia in lobster and in Squilla.