[Adrenal function in different phases of the estrous cycle in the domesticated silver fox, Vulpes fulvus].

Experiments were made on silver foxes from a population which had been selected for 10 to 15 generations for the domestic behaviour and on animals from a control, unselected population. In females from both populations, studies were made of the level of 11-OHCS in the blood serum, in vitro production of 11-OHCS, the size of fascicular zone in the adrenal cortex, the volume of cellular nuclei and nucleoli, as well as the reaction of the adrenals in vitro to 2 doses of ACTH (1 and 5 units/g of the adrenals) during anestrus, proestrus and estrus. In control females, all the characters investigated significantly increased from anestrus to proestrus. In domesticated females, no changes in the production of 11-OHCS in vitro or changes in morphological features of the fascicular zone were observed in the course of estrous cycle. During proestrus, the adrenals of the domesticated animals were not able to increase the production of 11-OHCS in vitro after application of ACTH. The decrease in the reactivity of the adrenals to the effect of ACTH is presumably the main cause why in unselected females the adrenal are not activated during proestrus. Therefore, in the course of selection for the domestication type of behaviour, species specific dynamics of activation of the adrenals during estrous cycle is lost.