Neural and glandular localisation of substance P in Echinostoma caproni (Trematoda-Digenea).

Immunocytochemical studies using antibodies against various peptides were performed on Echinostoma caproni. Only the presence of substance P or a related peptide was clearly demonstrated in this digenetic trematode. In the central nervous system, substance P-immunoreactive neurons were few and constituted two populations according to their size. Labelled axons were observed in the ventral and dorsal nerve cords. Scarce, small neurons and fibres were detected in the peripheral nervous system. The comparative study of 6- and 14-day-old worms showed an overall increase in substance P-immunoreactive nerve structures in the latter. Strong immunoreactivity for substance P was found in prostate cells from 14-day-old worms, whereas none was observed in 6-day-old worms. Thus, positive immunoreactivity seemed to be related to sexual maturity.