Effects of chronic treatment with propranolol or atenolol on stress-induced changes in blood pressure, body weight and cerebral β-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 β-adrenoceptors, but produced no changes in the cerebral α 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 β-adrenoceptors by 77% and reduced the downregulation induced by stress. Atenolol also increased the density of cerebral β-adrenoceptors by 34% and abolished the stress-induced downregulation in cerebral β-adrenoceptor density. In contrast, prazosin had no effect on the cerebral β-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 β-adrenoceptor transmission.
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