Is stimulation of prejunctional dopamine receptors an antihypertensive principle?

Bromocriptine and co-dergocrine (Hydergine R) reduce blood pressure and heart rate in experimental animals largely by stimulating DA2 receptors. A stimulant effect on DA1 receptors can be demonstrated in isolated tissues, but this action does not appear to make an important contribution to the depressor response to the two compounds, since effects are abolished by DA2 receptor blockade. Although both compounds are known to penetrate the brain, their antihypertensive effects, and the concomitant reductions in plasma noradrenaline levels produced in hypertensive patients can be prevented by domperidone, confirming a peripheral site of action. A review of the data available concerning the cardiovascular effects of bromocriptine and co-dergocrine in animals and man suggests that a DA2 receptor stimulant is effective in the treatment of hypertension.