Organization of ovine corticotropin-releasing factor immunoreactive neurons in the canine hypothalamo-pituitary system.

The distribution of corticotropin-releasing factor immunoreactive (CRF-i) cell bodies and varicose fibers in the hypothalamus and the pituitary of the canine brain was studied by indirect immunofluorescence. CRF-i cell bodies were demonstrated mainly in the periventricular zone of the third ventricle, while some CRF-i cell bodies were scattered throughout the ventral part of the caudomedial hypothalamus. CRF-positive fibers were mostly situated in the median eminence. In addition some CRF-positive fibers were detected in the ventromedial aspect of the lateral hypothalamus forming a pathway arising from the CRF-i cell bodies, running via the median eminence through the infundibular stalk and terminating in the pars nervosa of the pituitary. The localization of the cell bodies and their projection points towards a possible (patho)physiological role of this peptide-transmitter system in the release of ACTH and beta-endorphin.