EVIDENCE FOR A FMRFAMIDE-LIKE PEPTIDE IN THE HETERONEMERTINE CEREBRATULUS-LACTEUS LEIDY

Circular body wall muscles of Cerebratulus lacteus respond to micromol ar concentrations of the neuropeptide Phe-Met-Arg-Pheamide (FMRFa), fi rst isolated from molluscan nervous tissue. Comparison of the relative body wall contractural potencies of various FMRFa analogs indicates t hat the Arg-Pheamide group is necessary for this activity, but the rem aining N-terminal region can be altered considerably without loss of a ctivity. The circular muscle failed to respond to met-enkephalin and m any other vertebrate neuropeptides. Acetone-soluble extracts of Cerebr atulus contained two FMRFa antibody immunoreactive components separabl e by reversed phase liquid chromatography. Neither component had the s ame retention time as FMRFa. Bouin's fixed and paraffin embedded Cereb ratulus nervous tissues displayed specific immunofluorescence when inc ubated with FMRFa polyclonal antibody but not monoclonal antibody spec ific for the molluscan neuropeptide SCP-B. Some giant neuron somas in the lateral nerve cords and in the ventral cerebral ganglia were immun ochemically reactive as were axons in the lateral nerve cord and in th e circular and transverse body wall muscles. Pre-exposure of the antib ody with FMRFa prevented the reaction. Thus several types of evidence suggest the presence of FMRFa-like neuropeptides in Cerebratulus lacte us.