1. Bromocriptine (2.5 mg/day orally) produced a significant fall in supine mean arterial pressure in nine hypertensive haemodialysis patients with high serum prolactin levels, without causing significant changes in heart rate.
2. On bromocriptine, there was a significant decrease in the mean value of both serum prolactin and plasma noradrenaline, without significant changes in the mean value of plasma renin activity.
3. A significant relationship was found between the changes in supine plasma noradrenaline and the changes in supine mean arterial pressure induced by bromocriptine.
4. The increase in mean arterial pressure in response to the tilt test was greater on bromocriptine than on placebo although the changes in plasma noradrenaline were reduced by bromocriptine. Similar results were observed during the cold pressor test.
5. These findings suggest that the arterial pressure-lowering effect of bromocriptine is related to the reduction in sympathetic out-flow. The parallel decrease in serum prolactin raises the question of the possible involvement of dopaminergic mechanisms in the development of hypertension in our patients.
6. Moreover, bromocriptine seems to enhance the vascular response to endogenous noradrenaline.