AN IMMUNOCYTOCHEMICAL STUDY OF PUTATIVE NEUROTRANSMITTERS IN THE METACERCARIAE OF 2 STRIGEOID TREMATODES FROM RAINBOW-TROUT (ONCORHYNCHUS-MYKISS)

Whole mounts of the metacercariae of Diplostomum sp. and Cotylurus err aticus from rainbow trout have been treated cytochemically for the dem onstration of cholinergic, serotoninergic (5-hydroxytryptamine) and pe ptidergic elements in the nervous system. Antisera directed against fo ur vertebrate (pancreatic polypeptide, peptide YY, substance P and pep tide histidine isoleucine) and two invertebrate peptides (neuropeptide F and FMRFamide) were used in an indirect immunofluorescence procedur e in conjunction with confocal scanning laser microscopy (CSLM). Of th e seven antisera tested, all except peptide histidine isoleucine showe d significant immunoreactivity. Cholinergic and serotoninergic stainin g was found primarily in the central nervous system (CNS) and in cell bodies associated with the ventral and dorsal nerve cords in both trem atodes. Peptidergic immunoreactivity was localised in the CNS and PNS of both genera, revealing an extensive innervation within the holdfast organ and in and around the oral and ventral suckers.