Comparison of the Effects of 2-Deoxyglucose and Immobilization on Plasma Levels of Catecholamines and Corticosterone in Awake Rats

In rats, both forced immobilization and 2-deoxyglucose (2DG) administration evoke increases in sympatho-adrenal medullary release of catecholamines and adrenal cortical secretion of corticosterone. To examine the specificity and mediation by the central nervous system of these responses, plasma levels of epinephrine (from the adrenal medulla), norepinephrine (from sympathetic nerves), and corticosterone were determined during immobilization and after ip or intracerebroventricular administration of 2DG. After 2DG, plasma levels of epinephrine reached a peak within 15 min, while those of corticosterone were maximal at about 1 h. There was a clear relationship between dose of 2DG and the increases in epinephrine and corticosterone, but plasma levels of norepinephrine were increased only at the highest dose (1000 mg/kg) of 2DG. Severing the splanchnic nerve prevented the elevation in levels of epinephrine but did not alter the increase in corticosterone. The dose of 2DG (500 mg/kg) which elicited the same corticosterone response as did immobilization produced greater increases in epinephrine and smaller increases in norepinephrine than did immobilization. A relatively small dose (20 mg) of 2DG administered intracerebroventricularly evoked similar hormonal responses. Hypothalamic deafferentation attenuated the increases in plasma catecholamines evoked by either 2DG or immobilization. The results indicate that activities of both the adrenal medulla and the sympathetic nerves are enhanced during immobilization, whereas the adrenal medulla is selectively activated after 2DG. The effects of 2DG appear to result from its action in the brain, and the hypothalamus appears to be involved in mediating the sympathetic responses attending either stress.