Modulation of ciliary beat frequency by neuropeptides from identified molluscan neurons.

Prior work in the nudibranch Tritonia diomedea indicated that certain identifiable pedal ganglion neurons (Pd5 and 6) innervating the foot synthesize three novel peptides (TPeps) that resemble Pedal peptide (Pep) identified in the sea hare Aplysia californica. We report here that when TPeps are applied directly to isolated ciliated patches of Tritonia diomedea foot epithelium, there is an increase in ciliary beating that normally drives locomotion. Exposure to TPeps also increases the ciliary beat frequency of cells isolated from the pedal epithelium, suggesting that the observed ciliomotor effects are direct and not mediated by intervening cells. Antibodies to TPep bind to specific cells of the brain and foot and to ciliated peripheral tissues in Tritonia diomedea and in the pulmonate gastropod Lymnaea stagnalis. We suggest, therefore, that TPeps may regulate the activity of ciliated cells responsible for pedal locomotion and other functions in gastropod molluscs.