[Analysis of the mechanisms of refractivity of the pituitary-adrenal system in rat ontogeny].

In the course of postnatal ontogeny of rats, the synthesis and secretion of corticosterone after birth first decline, then increase by the 3d week of development, reaching by puberty the level seen in adult animals. During stressor stimulation with "neurogenic" stimuli (sound, swinging), the response on the part of the pituitary-adrenal system (PAS) is detectable only at the age of 3 weeks, whereas during immobilization of the animals with paw stretching and fixation it is detectable since the first day of life. The chemical stimulants of the adrenal cortex (ACTH), of the pituitary (vasopressin) and of the hypothalamus (insulin) activate the peripheral and central components of the PAS at varying age periods and to varying degree. This indicates that during early postnatal ontogenesis, the character of a stressor stimulus and line of its effect on different components of the system play the key roles.