Effects of adrenolytic drugs on the antihypertensive action of beta-blocking agents in the acute neurogenic hypertensive dog.

1. The antihypertensive action of three beta-blocking agents (dl-propranolol, dl-atenolol and butoxamine) was studied before and after pretreatment with adrenolytic drugs (reserpine and guanethidine) in acute neurogenic hypertensive (sino-aortic denervated) anesthetized dogs. 2. High doses of reserpine (2 mg/kg s.c.) suppressed both the effects of sino-aortic denervation and the antihypertensive action of dl-propranolol (1 mg/kg i.v.) 3. Pretreatment with reserpine (1 mg/kg i.p.) or guanethidine (15 mg/kg i.v.) delayed the manifestation of the antihypertensive action of dl-propranolol (1 mg/kg) observed in untreated (control) animals. 4. In a similar way, both dl-atenolol (1 mg/kg i.v.) and butoxamine (1 mg/kg i.v.) lost their antihypertensive effects after reserpinization. 5. These results indicate that the antihypertensive action of the three studied beta-blocking agents seen in debuffered animals depends upon the integrity of peripheral sympathetic nervous system under our experimental conditions. These effects are compatible with the view that beta-adrenoceptor blocking agents may exert, at least partly, their antihypertensive action through blockade of peripheral beta prejunctional adrenoceptors.