The effects of beta-adrenoreceptor blockers on blood pressure responses to central angiotensin II

Experiments were carried out in rats to study the effects of beta-adrenoreceptor blockade on the central angiotensin blood pressure responses. Immediately following acute administration of sotalol, l-propranolol and d-propranolol into the brain ventricles (i.c.v.), the beta-adrenoreceptor antagonists and d-propranolol produced transient increases of resting blood pressure, but they reduced the blood pressure increases following intraventricular injection of angiotensin II. Chronic oral beta-adrenoreceptor blockade with dl-propranolol racemate reduced heart rate in Wistar Kyoto rats and in spontaneously hypertensive rats. Mean arterial blood pressure decreased in spontaneously hypertensive rats but not in Wistar Kyoto rats. The blood pressure increases following intraventricular angiotensin II infusions were greater in spontaneously hypertensive than in Wistar Kyoto rats. Chronic oral propranolol treatment reduced the angiotensin II-induced blood pressure increases in Wistar Kyoto but not in spontaneously hypertensive rats. It is concluded that beta-adrenoreceptor blockers inhibit the blood pressure effects of brain angiotensin, but this appears not to be solely due to specific blockade of brain beta-adrenoreceptors.