Interaction of stress and ethanol: effect on β-endorphin and catecholamines
To examine the interaction of ethanol (ET) and stress on beta-endorphin and catecholamine (CA) levels, male rats pretreated with ET (3.0 g/kg, i.p.) or saline were immobilized for 30 min and killed 90 min after the initial injection. Stress resulted in (a) an increase in plasma levels of norepinephrine (NE, 243%), epinephrine (E, 175%), beta-endorphin (220%) and corticosterone (CS, 151%) and a decrease in dopamine (DA, 54%); (b) a decrease in hypothalamic NE (15%) and beta-endorphin (33%) levels and an increase E (23%) and DA (58%) levels; (c) a decrease in pituitary beta-endorphin levels in both the neurointermediate (23%) and anterior (131%) lobes. Treatment with ET resulted in: (a) an increase in plasma NE (81%), E (53%), CS (71%), and beta-endorphin (33%) levels and decrease in DA (54%); (b) a decrease in the hypothalamic NE (12%) levels and an increase DA (27%) and beta-endorphin (46%) levels, and (c) a decrease in beta-endorphin (15.5%) in the intermediate lobe of the pituitary. Treatment with ET of stressed animals had only a small effect: (a) in plasma NE, E, CS, and beta-endorphin levels decreased by 30, 31, 14, and 36%, respectively; (b) in the hypothalamus DA levels decreased by 40% and beta-endorphin increased by 71%; (c) in the pituitary beta-endorphin increased in both the intermediate lobe (25%) and anterior (50%) lobes. Thus when the data of the stressed ET-treated group is compared to that of the nonstressed saline injected group, none of the measures differ significantly. These results confirm our earlier work indicating a significant interaction of ET and stress.