Antihypertensive action of bromocriptine in neurogenic hypertensive dogs

The effects of bromocriptine, a dopamine agonist, were studied on blood pressure and heart rate in neurogenic hypertensive (sino-aortic denervated) anaesthetized dogs. Bromocriptine induced a very marked decrease in blood pressure but failed to modify the values of heart rate under our experimental conditions. This anti-hypertensive action of bromocriptine was abolished by pretreatment with dopamine antagonists: haloperidol, sulpiride or metoclopramide. Bilateral nephrectomy or ligature of both renal and mesenteric arteries (i.e. exclusion of the two major beds with postsynaptic dopaminergic receptors) failed to suppress the decrease in blood pressure elicited by bromocriptine in neurogenic hypertensive dogs. These results suggest that the antihypertensive action of bromocriptine in neurogenic hypertensive dogs was mainly due to an action on presynaptic and/or ganglionic peripheral dopaminergic receptors located on sympathetic nerve endings. The potential future importance of dopaminergic agonists as antihypertensive drugs is discussed.