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[Role of brain noradrenergic mechanisms in disturbing the circadian rhythm of the functioning hypothalamo-hypophyseo-adrenal cortex system in white rats in early ontogeny].


PMID 3008058

Abstract

The effects of hormone action and disturbance in catecholamine synthesis in the early postnatal ontogenesis on the circadian rhythm in the hypothalamic-hypophysial-adrenocortical system function were compared in the adult albino rat males. Injection of prednisolone on the 17-19th days of life blocked completely the diurnal rhythm of the corticosterone basal level in blood, the rhythm of adrenocortical response to an emotional stressor and to injection of noradrenaline into the brain lateral ventricle in 3-4 month old animals. Injection of an inhibitor of tyrosine hydroxylase, alpha-methyl-p-tyrosine, at the same period resulted in disappearance of the diurnal rhythm of the corticosterone basal level in adult animals, although the rhythm of response to an emotional stressor or injection of noradrenaline into the brain remained unchanged. A conclusion has been reached that disturbances in catecholamine synthesis in the early postnatal period induces long-term changes of predominantly tonic corticosterone secretion, while the hormone action on the circadian rhythm of the corticosterone basal level and stress response is only partly due to changes in noradrenergic regulation of the hypothalamic-hypophysial-adrenocortical system.