ELECTRON IMMUNOGOLD LABELING OF REGULATORY PEPTIDE IMMUNOREACTIVITY IN THE NERVOUS-SYSTEM OF MONIEZIA-EXPANSA (CESTODA, CYCLOPHYLLIDEA)

An electron immunogold-labeling technique was used in conjunction with a post-embedding procedure to demonstrate for the first time the ultr astructural distribution of the parasitic platyhelminth neuropeptide, neuropeptide F (NPF), in the nervous system of the cestode Moniezia ex pansa. Two axon types, distinguished by their populations of different -sized electron-dense vesicles, were identified. Immunogold labeling d emonstrated an apparent homogeneity of PP, FMRFamide and NPF (M. expan sa) antigenic sites throughout the larger dense-cored vesicles within the central nervous system. Triple labeling clearly demonstrated the c o-localisation of immunoreactivities (IR) for NPF, PP and FMRFamide wi thin the same dense-cored vesicles. The presence of NPF-IR within the vesicles occupying the perikaryon of the neuronal cell body indicated that the peptides had undergone post-translational C-terminal amidatio n prior to entering the axon. Antigen pre-absorption experiments using NPF prevented labeling with either PP or FMRFamide antisera, and the failure of these antisera to block NPF-IR supports the view that some, if not all, of the PP/FMRFamide-IR is due to NPF-like peptides.