[Reaction of the sympathetic-adrenal medulla system in young rats of different age to subcutaneous administration of a cardiotoxic dose of noradrenaline].

A quantitative histo-fluorescent investigation of the adrenal medulla and cardiac sympathetic nerves in young rats of various age has demonstrated a high degree in development of the adrenal medulla and a low density in arrangement of fluorescent nervous terminals in the ventricular myocardium in 3-week-old rats. During this period the animals show a low sensitivity to the catecholamine stress. At the age of 1.5 months the development of the sympatho-adrenomedullary system reaches the level specific for a mature animal; sensitivity to the norepinephrine stress increases noticeably, manifesting as a sharp activation of catecholamines secretion by the adrenal medulla and a high lethality.