The essential action of propranolol in hypertension.

The unique action of propranolol and other beta blockers in lowering raised arterial pressure is discussed. Although the onset of the antihypertensive effect is not immediate, many trials have confirmed the efficacy of these drugs. Animal experiments have thrown little light on the mechanism of action of beta blockers in hypertension: this may be because in animals, especially the rat, peripheral beta adrenoceptor vasodilatation is relatively more important than in man. Five principal theories have been advanced to explain the antihypertensive effect. None of these, the renin, central nervous system, cardiac, baroceptor or metabolite theory, is totally satisfactory. A new theory is proposed suggesting that the essential action is to diminish sympathetic nerve output by damping sensory input to the central nervous system from a heart whose capacity to respond to exercise and stress is blunted by beta adrenoceptor blockade.