Meeting Abstract

23.5  Jan. 5  Anterior cluster serotonergic neurons in the cerebropleural complex of Melibe leonina and their effects on other neurons MCPHERSON, D.R.; SUNY Geneseo mcpherso@geneseo.edu

Like many other opisthobranch mollusc species, the nudibranch Melibe leonina has two bilaterally symmetrical clusters of serotonergic neurons in the anterior region of the cerebropleural complex of the central nervous system. This region corresponds to the anterior part of the cerebral ganglia in species with separate cerebral and pleural ganglia. In most species there is a symmetrical pair of relatively large cells, the metacerebral giant cells, which are involved in feeding behavior. Relatively little is known about the function of the other anterior serotonergic neurons in behavior, but the homologous neurons in Clione limacina have an excitatory effect on the central pattern generator for swimming. I have begun examining the effects of the activity of the anterior serotonergic neurons in an isolated brain preparation of Melibe. The metacerebral giant cells are not distinguishable by size, because many of the neighboring serotonergic neurons are comparably large. Pairwise intracellular recordings indicate that some of the serotonergic neurons have a slow excitatory effect on neurons in the pedal ganglia, and extracellular recordings from the pedal commissure indicate that some of the serotonergic neurons project directly to the pedal ganglia. These results suggest that their behavioral function in Melibe may parallel that observed in Clione. Supported in part by a Research Incentive grant from SUNY Geneseo.