Cerebral-abdominal interganglionic coordinating neurons in Aplysia

Three cerebral-abdominal interneurons (CAIs), CC2, CC3, and CC7, were ident ified in the cerebral ganglion C cluster. The cells send their axons to the abdominal ganglion via the pleural-abdominal connective. CC2 and CC3 are b ilaterally symmetrical cells, whereas CC7 is a unilateral cell. CC3 is immu nopositive for serotonin and may be the same cell (CB-1) previously describ ed as located in the B cluster rather than the C cluster. We suggest that t he full designation of CC3, be CC3( CB-1). All three cells respond to feedi ng-related inputs. Each CAI has a monosynaptic connection to at least one a bdominal ganglion neuron involved in the control of various nonsomatic orga ns. The CAIs also exert widespread polysynaptic actions in the abdominal an d head ganglia. The results suggest that the CAIs may act as interneurons t hat coordinate visceral responses mediated by the abdominal ganglion, with behaviors such as feeding and head withdrawal, that are controlled by neuro ns located in the head ganglia of the animal.