Evidence for a FMRFamide-like peptide in the heteronemertine Cerebratulus lacteus Leidy

Abstract

Circular body wall muscles of Cerebratulus Zacteus respond to micromolar concentrations of the neuropeptide Phe-Met-Arg-Pheamide (FMRFa), first isolated from molluscan nervous tissue. Comparison of the relative body wall contractural potencies of various FMRFa analogs indicates that the Arg-Pheamide group is necessary for this activity, but the remaining N-terminal region can be altered considerably without loss of activity. The circular muscle failed to respond to met-enkephalin and many other vertebrate neuropeptides.Acetone-soluble extracts of Cerebratulus contained two FMRFa antibody immunoreactive components separable by reversed phase liquid chromatography.Neither component had the same retention time as FMRFa. Bouin's fixed and paraffin embedded Cerebrutulus nervous tissues displayed specific immunofluorescence when incubated with FMRFa polyclonal antibody but not monoclonal antibody specific for the molluscan neuropeptide SCP-B. Some giant neuron somas in the lateral nerve cords and in the ventral cerebral ganglia were immunochemically reactive as were axons in the lateral nerve cord and in the circular and transverse body wall muscles. Pre-exposure of the antibody with FMRFa prevented the reaction. Thus several types of evidence suggest the presence of FMRFa-like neuropeptides in Cerebratulus lacteus.