PEPTIDE F-1, AN N-TERMINALLY EXTENDED ANALOG OF FMRFAMIDE, ENHANCES CONTRACTILE ACTIVITY IN MULTIPLE TARGET TISSUES IN LOBSTER

摘要

The physiological actions of lobster peptide Fl (TNRNFLRFamide) have been examined on three different lobster nerve-muscle preparations (exoskeletal, cardiac and visceral). The peptide, which is found at high concentrations in a lobster neurosecretory gland, causes a long-lasting enhancement of contractility in each target tissue, On exoskeletal nerve-muscle preparations, peptide F-1 has the following actions: (1) it potentiates transmitter release from nerve terminals innervating exoskeletal muscle, leading to an increase in both spontaneous and nerve-evoked release of transmitter; (2) it acts directly on the muscle, in the absence of nerve activity, to induce tonic contractions; and (3) it shows a potent desensitization that does not reverse with prolonged washing of the tissue, On each of the types of muscle examined, peptide F-1 is active at nanomolar concentrations and is 3-4 orders of magnitude more potent than FMRFamide. These findings suggest that peptide F-1 is a neurohormone with widespread myogenic actions throughout lobster peripheral tissues, The molecular mechanism(s) by which the peptide acts are not yet known, but do not appear to involve cyclic AMP or cyclic GMP. [References: 57]