ABSTRACT
Each of the two gastro-oesophageal ganglia of the nudibranch mollusc, Anisodoris nobilis, contains one giant neurone (G cell) whose axon is directed toward the oesophagus in the gastro-oesophageal nerve.
In the absence of stimulation the G cells are normally silent. However, they receive inhibitory and excitatory synaptic inputs from more central ganglia and a predominantly excitatory input from the periphery. The inputs from the central ganglia are bilaterally distributed to both G cells, whereas the inputs from the periphery are limited to the ipsilateral G cell.
Intracellular stimulation shows that there is no interaction between the G cells, nor between the G cell and other cells in the same or contralateral gastro-oesophageal ganglia.
The axon of the G cell makes synaptic contact with a series of peripheral cells (P cells). In most P cells the post-synaptic potential elicited by intracellular stimulation of the G cell is constant in amplitude and latency and probably results from a unitary monosynaptic contact. Intracellular stimulation shows that the P cells are not connected to the G cell.
The P cells are inter-connected by low-resistance electrotonic junctions which allow slow potentials of either polarity to spread between cells. These junctions exist between distant as well as adjacent peripheral neurones.
Our results show that the G cell functions as a command interneurone for an aggregate of electrically interconnected peripheral neurones.
