Modulatory command function of the metacerebral cell on feeding behavior in aplysia

The metacerebral cell (MCC) is a serotonergic neuron sending axons to the buccal muscles and ganglia involved in feeding. Although firing the MCC intracellularly did not lead to buccal muscle contraction, it produced a large increase of the contraction elicited by direct stimulation of identified motor neurons innervating muscle. The maximum effect occurred 30 sec after MCC stimulation, and persisted for minutes. Firing the MCC did not produce any alteration of muscle membrane potential. Although, after MCC stimulation, there are some alterations of the e.j.p. produced by the motor neuron, the overall data suggest that the increased contraction results from a direct effect of the MCC on the muscle. These results support the notion that the MCC exerts a modulatory role in feeding behavior. The multiplicity of central actions of the MCC, as well as its peripheral actions, suggest that it is exerting a command like function; however, it may primarily affect the intensity rather than sequencing parameters of feeding behavior.