Serotonin inhibits ciliary transport in esophagus of the nudibranch mollusk Tritonia diomedea

Both serotonin and the molluskan pedal neuropeptides (TPEPs) cause increase d ciliary beating rate of cells of the foot epithelium of the nudibranch mo llusk, Tritonia diomedea. Here we compared responses of the ciliated epithe lium of the esophagus with that of the foot, and report fundamental differe nces. Serotonin reduces the ciliary transport rate of the esophagus. We fin d also that the serotonin driven inhibition of esophagus is blocked and the excitation of foot epithelium is reduced by the serotonin receptor blocker ketanserin. On the contrary ergometrine completely blocked the serotonin e ffect in the esophagus, and does not block the serotonin effect in the foot . Neither the TPEP driven excitation of ciliated cells of the foot nor that of the esophagus is blocked by ketanserin and ergometrine. Clearly, seroto nin and TPEP regulation of different ciliated epithelia involve different r eceptors. Thus, mechanisms of serotonin control of different ciliated epith elia in the same animal are apparently fundamentally different, and unlike responses in all previous reports, 5HT here inhibits a ciliated epihelium.