PHYSIOLOGICAL-EFFECTS OF PLATYHELMINTH RFAMIDE PEPTIDES ON MUSCLE-STRIP PREPARATIONS OF FASCIOLA-HEPATICA (TREMATODA, DIGENEA)

The effects of each of the known platyhelminth neuropeptides were dete rmined on muscle-strip preparations from the liver fluke, Fasciola hep atica. The activity of synthetic replicates of the C-terminal nonapept ide of neuropeptide F (NPF9, Moniezia expansa), and the FMRFamide-rela ted peptides (FaRPs), GNFFRFamide, RYIRFamide, GYIRFamide and YIRFamid e, were examined. Muscle-strip activity was recorded from 1 mm segment s of muscle prepared from 28 to 32-day-old worms, using a photo-optic transducer system. None of the peptides (less than or equal to 10 mu M ) altered baseline tension significantly; however, each of the peptide s increased the amplitude and frequency of muscle contraction. The thr eshold for activity of each of the peptides examined was, respectively , 1 nM (RYIRFamide), 0.3 mu M (GYIRFamide and YIRFamide), and 10 mu M (GNFFRFamide and NPF9). All of the effects were reversible and repeata ble, following wash-out. Muscle-strip integrity was tested following e xperimentation, using arecoline (10 mu M) and high-K+ bathing medium ( 90 mM K+).