[Seasonal changes in the reaction of the hypophyseal-adrenal system to adrenomimetics in the suslik Citellus erythrogenys].

Studies have been made on the reaction of the hypophysial-adrenal system to the injection of adrenalin and novodrin to the ground squirrel C. erythrogenys at various seasons of year and at different functional conditions of the animals. Together with seasonal variations in the basal level of corticosteroids in the peripheral blood, seasonal changes in the reaction of non-hibernating animals to adrenomimetics were found. Stimulating effect of the adrenomimetics was higher at spring, immediately after awakening, being significantly lower in summer and being absent before the onset of hibernation. At the same time, the sensivity of the adrenal cortex to ACTH was relatively high. Presumably, seasonal changes in the reaction of the hypophysial-adrenal system in the ground squirrels to adrenomimetics are associated either with changes in the sensitivity of the adrenoreceptors, or with changes in the reactivity of the central part of the hypothalamo-hypophysial-adrenal system.