Effects of propranolol and atenolol on immobilization stress-induced hypertension and down-regulation of central beta-adrenoceptors in rats.

摘要

Effects of chronic treatment with propranolol or atenolol on stress-induced changes in blood pressure, body weight, and cerebral beta-adrenoceptors in rats were examined and compared with the effects of chronic treatment with prazosin. Immobilization stress (2 h daily for 2 weeks) induced a moderate elevation of blood pressure, loss of body weight gain, and downregulation of cerebral beta-adrenoceptors, but produced no changes in the cerebral alpha 1-adrenoceptors. Chronic administration of propranolol (5 or 50 mg.kg-1), atenolol (5 or 50 mg.kg-1) or prazosin (2 or 20 mg.kg-1) inhibited stress-induced hypertension but did not affect loss of body weight gain. Propranolol increased the density of cerebral beta-adrenoceptors by 77% and reduced the downregulation induced by stress. Atenolol also increased the density of cerebral beta-adrenoceptors by 34% and abolished the stress-induced downregulation in cerebral beta-adrenoceptor density. In contrast, prazosin had no effect on the cerebral beta-adrenoceptors in nonstressed or stressed rats. These results suggest that the antihypertensive action of propranolol and atenolol may be partly associated with the inhibition of stress-activated central beta-adrenoceptor transmission.