THE DISTRIBUTION OF CORTICOTROPIN-RELEASING FACTOR IMMUNOREACTIVE NEURONS AND NERVE-FIBERS IN THE BRAIN OF GAMBUSIA-AFFINIS AND SALMO-TRUTTA

The study was carried out on the distribution of neurons and fibres wh ich contain the Corticotropin releasing factor-like (CRF) immunoreacti vity in the encephalon of two Species of teleosts, Gambusia affinis an d Salmo trutta. The peroxidase-antiperoxidase (PAP) immunocytochemical technique was employed. The present study has shown differences betwe en both species. In Gambusia affinis, positive neurons were observed i n the area ventralis telencephali pars lateralis (VLT), in the nucleus praeopticus (NPO) and in the nucleus lateralis tuberis (NLT). The imm unoreactive fibres were in the area ventralis telencephali, in the pre optic hypophyseal tract and in the hypophysis. In Salmo trutta the imm unoreactive cells were seen in the pars magnocellularis and pars parvo cellularis of the NPO and in cerebrospinal fluid (CSF) contacting neur ons of the NLT. The pattern of distribution of immunoreactive fibres i n Salmo trutta was different from that in Gambusia affinis. In additio n to the distribution of perikarya in Gambusia affinis (in the VLT and in the preoptic hypophyseal tract), fibres were also observed in the tubero-hypophyseal tract and in the posterior hypothalamus. The hypoph ysis of Salmo trutta also presents an extensive labelling. The intersp ecific differences shown in the present study should be due to the dif ferent degree of evolution in the two species studied and to other cau ses, such as environmental ones.