[The effect of prolonged exposure to gamma rays and hormonal stimulation with serum gonadotropin on the levels of catecholamines in the hypothalamus, epiphysis and adrenal glands in sheep].

The effect of the exposure of the whole body to continuous radiation and of the administration of serum gonadotropin (SG) was studied as exerted on the concentration of catecholamines (epinephrine and norepinephrine) in the hypothalamus, epiphysis and adrenal glands of ewes during the anoestric period with synchronized oestrus. The first group (young barren ewes) and second group (older ewes) were exposed to continuous radiation of 60Co for five days. The radiation was provided at the rate of 0.020 Gy per hour. After the termination of irradiation the ewes were subjected to hormonal stimulation by fractionated administration of 1500 I. U. SG. The third and fourth experimental groups of ewes were stimulated with 1500 I. U. SG without irradiation. Catecholamines were separated from the tissue supernatants by the adsorption chromatographic method and the catecholamine contents in the eluates were determined spectrofluorometrically. Protracted exposure to gamma radiation and hormonal stimulation with SG reduces the concentration of norepinephrine in the whole hypothalamus of the sheep. A statistically significant decrease (P less than 0.001) was recorded in the medial and caudal hypothalamus of the adult ewes and in the rostral and caudal hypothalamus regions of the young ewes. A decrease of norepinephrine concentration, statistically significant in the caudal (P less than 0.01) and medial hypothalamus, was recorded in the group of adult ewes after hormonal stimulation with SG without irradiation. The experimental group of young ewes responds to hormonal stimulation by a greater reduction of norepinephrine contents, as compared with combined exposure to radiation and hormonal stimulation. It is assumed that the decrease in catecholamine concentration after hormonal stimulation with SG is associated with the increase in the content of oestrogens, which act on the adrenergic receptors of the hypothalamus.