ULTRASTRUCTURAL-LOCALIZATION OF FMRFAMIDE-IMMUNOREACTIVITY AND PANCREATIC POLYPEPTIDE-IMMUNOREACTIVITY WITHIN THE CENTRAL-NERVOUS-SYSTEM OFTHE LIVER FLUKE, FASCIOLA-HEPATICA (TREMATODA, DIGENEA)

A post-embedding immunogold technique was used to examine the subcellu lar distribution of immunoreactivities to the invertebrate peptide, FM RFamide, and to vertebrate pancreatic polypeptide (PP) within the cent ral nervous system of the trematode, Fasciola hepatica. Gold labeling of peptide was localised exclusively over both dense-cored and ellipso idal electron-dense vesicles (with a homogeneous matrix) present withi n nerve cell bodies, small and 'giant' nerve processes of the neuropil e in the cerebral ganglia and transverse commissure, as well as in the main longitudinal nerve cords. Double labeling demonstrated an appare nt co-localisation of FMRFamide and PP immunoreactivities in the same dense-cored vesicles, although populations of ellipsoidal electron-den se vesicles that labeled solely for FMRFamide were also evident. Antig en pre-absorption studies indicated little, if any, cross-reactivity o f the two antisera.