[Mechanisms of seasonal changes in the circadian corticosteroid function of rats].

Data are presented concerning seasonal changes in the circadian 11-OCS rhythm in the adrenal glands in the plasma of rats. For the purpose of studying the mechanisms of control of circadian 11-OCS rhythms during the spring and autumn seasons there were studied circadian corticosteroid reactions to ACTH and stress. The "Cosinor" method of study was used for analysis of the real circadian rhythm. The data obtained permit to suppose that in autumn the rhythm of the adrenal glands was associated with the circadian rhythm of the central links of the hypothalamo-hypophyseo-adrenal system, and during the spring season an important contribution in the formation of the circadian rhythm of the adrenocortical activity was brought by the adrenal mechanisms.