Physiological effects of platyhelminth RFamide peptides on muscle-strip preparations ofFasciola hepatica(Trematoda: Digenea)

Abstract

SUMMARYThe effects of each of the known platyhelminth neuropeptides were determined on muscle-strip preparations from the liver fluke, Fasciola hepatica. The activity of synthetic replicates of the C-terminal nonapeptide of neuropeptide F (NPF9, Moniezia expansa), and the FMRFamide-related peptides (FaRPs), GNFFRFamide, RYIRFamide, GYIRFamide and YIRFamide, were examined. Muscle-strip activity was recorded from 1 mm segments of muscle prepared from 28 to 32-day-old worms, using a photo-optic transducer system. None of the peptides (≤ 10 μM) altered baseline tension significantly; however, each of the peptides increased the amplitude and frequency of muscle contraction. The threshold for activity of each of the peptides examined was, respectively, 1 nM (RYIRFamide), 0·3 μM (GYIRFamide and YIRFamide), and 10 μM (GNFFRFamide and NPF9). All of the effects were reversible and repeatable, following wash-out. Muscle-strip integrity was tested following experimentation, using arecoline (10 μM) and high-K+ bathing medium (90 mM K+).

The musculature and associated innervation of adult and intramolluscan stages of Echinostoma caproni (Trematoda) visualised by confocal microscopy

“…1) have shown the presence of cholinergic/inhibitory and aminergic/excitatory systems, consistent with those found in other trematodes examined (Humphries et al 2000). Also, exogenous application of any one of the four known flatworm FMRFamide-related peptides (FaRPs) to muscle-strip preparations of E. caproni gave results in accord with those reported for the liver fluke, Fasciola hepatica (Marks et al 1996). The order of potency of these neuropeptides on echinostome motility was: GYIRFamide (isolated from Girardia tigrina, Bdelloura candida) > RYIRFamide (Arthurdendyus triangulatus) = YIRFamide (Bdelloura candida) > GNFFRFamide (Moniezia expansa).…”

Echinostomes as Experimental Models for Biological Research

“…The total inventory of flatworm neuropeptides to date is 6. The results are in accord with those reported for other flatworms, including F. hepatica, where the same peptides as were used with E. caproni were tested on muscle-strip preparations of the worm (Marks et al, 1996). Preliminary tests in our laboratory showed that the exogenous addition of anyone of these peptides to intact specimens of E. caproni was without effect, necessitating the worms being cut just posterior to the acetabulum in order to facilitate peptide penetration.…”

Neuroactive substances and associated major muscle systems in Bucephaloides gracilescens (Trematoda: Digenea) metacercaria and adult

“…In addition, this biogenic amine is believed to be important in maintaining neuroplasticity in invertebrates and in the generation of muscle and nerve (Mitchell et al 2001). Although still not well understood, physiological studies so far have shown FaRPs to be myoexcitatory, inducing dose-dependent contractions in vitro of isolated muscle fibres from S. mansoni (Day et al 1994) and the marine turbellarian, Bdelloura candida and muscle strips from Fasciola hepatica (Marks et al 1996;Graham et al 1997).…”