IMMUNOCYTOCHEMICAL LOCALIZATION OF SEROTONIN (5-HT) IN THE NERVOUS-SYSTEM OF THE HYDATID ORGANISM, ECHINOCOCCUS-GRANULOSUS (CESTODA, CYCLOPHYLLIDEA)

The localization and distribution of the serotoninergic components of the nervous system in the hydatid organism, Echinococcus granulosus, w ere determined by immunocytochemical techniques in conjunction with co nfocal scanning laser microscopy (CSLM). The distribution of serotonin immunoreactivity (IR) paralleled that previously described for cholin esterase activity, although it was more widespread. Nerve cell bodies and nerve fibres immunoreactive for 5-HT were present throughout the c entral nervous system (CNS), occurring in the paired lateral, posterio r lateral and rostellar ganglia, their connecting commissures and nerv e rings in the scolex and in the ten longitudinal nerve cords that run posteriorly throughout the body of the worm. A large population of ne rve cell bodies was associated with the lateral nerve cords. In the pe ripheral nervous system (PNS), immunoreactive nerve fibres occurred in well-developed nerve plexuses innervating the somatic musculature and the musculature of the rostellum and suckers. The genital atrium and associated reproductive ducts were richly innervated with serotoninerg ic nerve cell bodies and nerve fibres.