[Morphologic and biochemical changes in the hypothalamus in hormonally stimulated sheep].

The effect of exogenous hormonal preparations (PMSG, SG, PMSG + PGF2 alpha and FSH) was studied as exerted on neurosecretion and on changes in the nuclear volume of nucleus paraventricularis, nucleus ventromedialis, nucleus infundibularis and nucleus tuberomamillaris, and on histological changes in the third cerebral ventricle. Changes in catecholamine concentrations were determined in the rostral, medial, and caudal hypothalamus of the ewes. The study was performed with 28 ewes of the Slovak Merino breed during the oestrus period. The oestrus was synchronized by the Agelín vaginal tampons (Spofa). The ewes of four experimental groups were stimulated by the administration of 1000 I.U. PMSG (Antex-Leo), 1000 I. U. Serum Gonadotropin (Bioveta Ivanovice na Hané), 1000 I. U. PMSG with 250 micrograms Oestrophan inj. (Léciva Praha), and 450 I. U. Folistiman (VEB Arzneimittelwerk Dresden, GDR). The brain samples were processed by common histological methods. A caryometric analysis was performed at 3000-fold magnification and by measurement of 200 cells of one sample. The data were subjected to mathematical processing after Fischer and Inke (1956). The amount of neurosecretory material was evaluated by light microscopy (Nakahara, 1963). The multiplication of neurosecretion in the hypothalamic nuclei testifies to the fact that the administration of hormonal preparations stimulates the function of hypothalamic structures, which corresponds with the results of the caryometric analysis. It also ensues from the results that the administration of serum gonadotropins (PMSG and SG) at the dose of 1000 I. U. results in a statistically significant decline (P less than 0.001) of the concentrations of norepinephrine in the rostral, medial and caudal hypothalami of the ewes, although the PMSG preparation has a more pronounced effect when compared with SG. The hormonal stimulation with PGF2 alpha and with FSH causes no significant changes in the concentration of norepinephrine in the hypothalamus of the ewes. As norepinephrine is considered as a neurosecretion inhibitor, the multiplication of neurosecretion in the hypothalamus nuclei after stimulation with serum gonadotropins correlates with the decline of hypothalamic norepinephrine concentrations.