THE HYPOTHALAMO-HYPOPHYSEAL SYSTEM IN ACIPENSERIDAE .11. MORPHOLOGICAL AND IMMUNOHISTOCHEMICAL ANALYSIS OF NONAPEPTIDERGIC AND CORTICOLIBERIN-IMMUNOREACTIVE ELEMENTS IN HYPOPHYSECTOMIZED STERLET (ACIPENSER-RUTHENUS L)

The regeneration of the hypothalamo-hypophyseal system (HHS) has been studied in the sterlet following hypophysectomy (HypoX). Significant p ortions of nonapeptide and corticoliberinergic (CRH) neurosecretory ce lls (NSCs) underwent degeneration. Surviving NSCs had a great regenera tive ability; damaged axons formed anew uncharacteristicly for intact fishes, axovasal and axovenhicular contacts. There are some specific f eatures of the reorganization of the ANHyp in sterlet after HypoX: (a) blood capillaries from the meninges penetrate deep into the wall of t he infundibular recess and form unusual axovasal contacts; (b) ''neuro vascular regeneratory complexes'' appear; (c) single CRH-immunoreactiv e axons grow into the meninges. Morphological data show progressive ap pearance of dendroventricular contacts in the preoptic nucleus, format ion of new axoventricular and axovasal contacts, and activation of sur viving NSCs after HypoX. An ability to reorganize HHS to release neuro hormones into the CSF and bloodstream is suggested. (C) 1997 Academic Press.