Dissociation of catecholamine and corticosterone responses to different types of stress in rats.

To examine hormonal response patterns to various stresses, urinary excretion of catecholamines and corticosterone was measured in spontaneously hypertensive rats (SHR) and Wistar-Kyoto normotensive rats (WKY) under the following conditions: immobilization, restriction to a small space, introduction of new rats, and noise exposure. In WKY rats, immobilization caused a marked increase in urinary corticosterone, adrenaline and noradrenaline and a decrease in dopamine excretion. Restriction to a small space induced a less pronounced but still obvious increase in adrenaline and corticosterone and a decrease in dopamine. When other rats were introduced into the animal room, the senior rats showed an increase in adrenaline alone, while noise exposure produced an increase in corticosterone alone. These findings suggest that while severe stress, such as immobilization, causes marked changes in all 4 hormones, relatively mild stress produces changes in one to three, not all, hormones, and that catecholamine and corticosteroid responses are dissociated in some forms of the mild stress. It is considered that neuroendocrine responses to stress vary according to both the type of stress and its intensity. In SHR rats, the hormone response to severe stress was greater than in WKY rats, and the response was somewhat less than in WKY rats when exposed to mild stress. These findings do not imply that stress-induced hyperactivity of sympathetic adrenomedullary system participates in the development of hypertension in SHR rats.