Egestive feeding responses in Aplysia persist after sectioning of the cerebral–buccal connectives: evidence for multiple sites of control of motor programs

Abstract

Ingestive and egestive behaviors in Aplysia are generated by motor neurons and interneurons chiefly located in the buccal ganglion, but cerebral ganglion neurons appear to contribute to both ingestive and egestive motor programs. We investigated if the cerebral ganglion input to the buccal ganglion is necessary for the generation of buccal ingestive and egestive behaviors in free-moving animals. We confirmed a prior study that showed that animals with lesions of the cerebro-buccal connectives (CBCs) do not exhibit rhythmic biting following seaweed stimulation of the lips, but do show swallowing of seaweed inserted into the buccal cavity. We found that CBC-lesioned animals also exhibited rejection of a tube inserted into the buccal cavity and esophagus. The programs for swallowing and rejection behaviors were similar to those observed before lesioning the CBCs, although the rate of swallowing was slower. These results suggest that the cerebral input to the buccal ganglion is necessary for generating biting responses, but is not required for producing swallowing or rejection responses.