DISSOCIATION OF CATECHOLAMINE AND CORTICOSTERONE RESPONSES TO DIFFERENT TYPES OF STRESS IN RATS

To examine hormonal response patterns to various stresses, urinary exc retion of catecholamines and corticosterone was measured in spontaneou sly hypertensive rats (SHR) and Wistar-Kyoto normotensive rats (WKY) u nder the folowing conditions: immobilization, restriction to a small s pace, introduction of new rats, and noise exposure. In WRY rats, immob ilization caused a marked increase in urinary corticosterone, adrenali ne 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 fn dopamine. When oth er rats were introduced into the animal room, the senior rats showed a n increase in adrenaline alone, while noise exposure produced an incre ase in corticosterone alone. These findings suggest that while severe stress, such as immobilization, causes marked changes in all 4 hormone s, relatively mild stress produces changes in one to three, not all, h ormones, and that catecholamine and corticosteroid responses are disso ciated in some forms of the mild stress. It is considered that neuroen docrine 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 t hat stress-induced hyperactivity of sympathetic adrenomedullary system participates in the development of hypertension in SHR rats.