THE EFFECTS OF FARPS ON THE MOTILITY OF ISOLATED MUSCLE STRIPS FROM THE LIVER FLUKE, FASCIOLA-HEPATICA

The effects of a range of FMRFamide-related peptides (FaRPs) on isomet ric contractility were tested using isolated muscle strips from the li ver fluke, F. hepatica. The neuropeptides tested were the molluscan Fa RPs, FMRFamide and FLRFamide, the turbellarian FaRPs, RYIRFamide and G YIRFamide, the cestode peptides, NPF and GNFFRFamide, and the nematode FaRPs, AF-1 (KNEFIRFamide), AF-2 (KHEYLRFamide), AF-8 (KSAYMRFamide), and PF-4 (KPNFIRFamide). Dose-response experiments were undertaken at a concentration range of 5 nM-5 mu M for all of the neuropeptides tes ted. FMRFamide and AF-8 caused statistically significant increases in the amplitude and frequency of contractions at concentrations of 0.5 m u M and 5 mu M. FLRFamide and AF-2 also caused significant increases i n contraction frequency at concentrations of 0.5 mu M and 5 mu M, alth ough a significant increase in amplitude of contraction was observed o nly at a concentration of 5 mu M. GYIRFamide increased both amplitude and frequency significantly at concentrations of 50 nM, 0.5 mu M and 5 mu M. RYIRFamide significantly increased frequency of contractions at concentrations of 0.5 mu M and 5 mu M, but failed to have a significa nt effect on contraction amplitude. AF-1 at a concentration of 5 mu M increased contraction amplitude, but failed to have an effect on frequ ency at any of the concentrations used. PF-4 caused a statistically si gnificant increase in both the amplitude and frequency of contractions at a concentration of 5 mu M. NPF and GNFFRFamide had no effect on th e in vitro motility of F. hepatica over the range of concentrations te sted. The results are discussed in the light of possible structure-act ivity relationships in the FaRPs tested.