Immunohistochemical localization of corticotropin-releasing factor in the brain and corticotropin-releasing factor and thyrotropin-stimulating hormone in the pituitary of Chinook salmon (Oncorhynchus tshawytscha)

This report describes the distribution of corticotropin-releasing factor (C RF)-like immunoreactivity in the brain and the contiguous localization of C RF- and thyrotropin-stimulating hormone (TSH)-like immunoreactivity in the pituitary of hatchery-reared, juvenile chinook salmon (Oncorhynchus tshawyt scha). Results show that CRF-immunoreactive cell bodies exist in the parvoc ellular and magnocellular nuclei of the preoptic area and in a ventral hypo thalamic region corresponding to the nucleus lateralis tuberis. CRF-immunor eactive fibers are observed along the rostral edge of the hypothalamus, in the pituitary stalk, and in the pituitary gland. Within the pituitary, CRF- immunoreactive fibers, with terminal-like boutons, were distinguishable in the neurohypophysis, pars distalis (PD), and pars intermedia (PI). In the P D, the CRF-immunoreactive fibers terminate in regions that contain TSH-posi tive pituitary cells. From this study, we conclude that CRF-immunoreactive fibers travel through, and terminate in, the neurohypophysis. CRF-immunorea ctive fibers were also observed to terminate within the basement membrane a nd within the PD and PI of the adenohypophysis. Furthermore, the contiguous localization of CRF-immunoreactive fibers and TSH-immunoreactive pituitary cells suggests that CRF may mediate release of TSH. (C) 1999 Academic Pres s.