Neuropeptide TPep action on salivary duct ciliary beating rate in the nudibranch mollusc Tritonia diomedea.

Recently, in the marine mollusc Tritonia, a family of three peptides (TPep-NLS, -PLS, -PAR) from identified pedal ganglion neurons has been characterized and shown to regulate ciliary beat frequency in epithelia and isolated cells of the molluscan foot. In this study, using an antiserum raised against TPep-NLS, immunofluorescent labelling was observed in specific nerve cell bodies and axons in the buccal ganglia of Tritonia, as well as in axons leading to and innervating the salivary ducts, salivary glands, oesophagus and foregut. This pattern of innervation suggests that buccal ganglion neurons containing TPep control the beating rate of ciliated cells in feeding organs. Accordingly, TPeps were introduced to isolated ciliated salivary ducts. It was found that TPeps and serotonin increased the ciliary beat frequency of cells of the salivary duct similarly; other peptides (such as APep from Aplysia) had no such effect. Threshold sensitivity both for TPeps and serotonin was approximately 10(-8) M, with maximal response occurring above 10(-5) M. Taken together, these structural and physiological results suggest that TPep-like peptides are present in the salivary and other feeding organs of Tritonia and are involved in the regulation of salivary transport.