The presence of a SchistoFLRFamide-like peptide associated with the oviducts of Locusta migratoria has been shown using sequential reversed-phase high performance liquid chromatography separation coupled with radioimmunoassay and bioassay. The peptide is present in areas of the oviduct which receive extensive innervation, with sixfold less peptide in areas that receive little innervation. Material with FMRFamide-like immunoreactivity (determined by radioimmunoassay) is also present in the oviducal nerve and VIIth abdominal ganglion.
SchistoFLRFamide is a potent modulator of contraction of this visceral muscle, inhibiting or reducing the amplitude and frequency of spontaneous contractions, relaxing basal tonus, and reducing the amplitude of neurally-evoked, proctolin-induced, glutamate-induced and high potassium-induced contractions. The FMRFamide-like immunoreactivity within the oviducts which co-elutes with SchistoFLRFamide on two separations is also capable of reducing the amplitude of neurally-evoked and proctolin-induced contractions, and of inhibiting spontaneous contractions and relaxing basal tonus.
The effects of SchistoFLRFamide upon this visceral muscle are not abolished by the ~-adrenergic receptor antagonist phentolamine and do not appear to be mediated by cyclic AMP. Thus the receptors for Schisto-FLRFamide are distinct from those of octopamine which mediate similar physiological effects but which are blocked by phentolamine and which are coupled to adenylate cyclase.
The results indicate that SchistoFLRFamide, or a very similar peptide, which has previously been identified as a modulator of locust heart beat, is also associat-Abbreviations: BPP-Bovine pancreatic polypeptide; BSA -Bovine serum albumin; EJP-Excitatory junctional potential; FaRPs -FMRFamide-related peptides; FLI-FMRFamide-like immunoreactivity; LMS -Leucomyosuppressin; RIA -Radioimmunoassay; RP-HPLC -Reversed-phase high performance liquid chromatography; TFA -Trifluoroacetic acid * To whom offprint requests should be sent ed with visceral muscle of the reproductive system, and may play a neural role in concert with octopamine, at modulating muscular activity.