Age changes in the ultrastructure and function of rat adrenal glands during stimulation of the hypothalamus.

Studies were undertaken on the ultrastructure and function of the adrenal cortex and the adrenal medulla three hours after an electric stimulation of the ventromedial nucleus area of the hypothalamus in the adult and old albino rats. The electron microscopic and biochemical findings revealed a significant decrease in the hypothalamic control over catecholamine and corticosteroid syntheses in the old rats. The regulatory influence of the hypothalamus on the secretory activity of the adrenocortical and adrenomedullar cells showed an irregular pattern of changes during aging, i.e. a more marked impairment of the adrenal medulla and a less marked impairment of the cortex.