Prevention and reversal of isolation-induced systolic arterial hypertension in rats by treatment with beta-adrenoceptor antagonists.

1. Rats were made hypertensive by 5 days of continuous isolation in glass metabolic cages; in the text "hypertensive" means having a systolic blood pressure greater than 145 mmHg. 2. Daily intraperitoneal injections of either propranolol (5 mg/kg) or atenolol (5 mg/kg) reduced systolic blood pressure within 3 days and the systolic blood pressure remained low provided that the treatment was continued. 3. Treatment with metoprolol also lowered the systolic blood pressure of isolated rats but only when a larger dose (10 mg/kg) was given. 4. Systolic blood pressure returned to hypertensive levels following withdrawal of treatment after 15 days of isolation. However, following cessation of treatment after 27 days of isolation, the systolic blood pressure did not rise. 5. Rats given propranolol in the drinking water (intake equivalent to a daily dose of 5 mg/kg) before and during isolation did not develop hypertension. 6. The possibility that suppression of sympathetic function by the beta-adrenoceptor antagonists was responsible for these changes is discussed.