Is normoreninemic essential hypertension caused by disordered central dopaminergic regulation?

Some investigators have reported that plasma prolactin levels are elevated in hypertensive men and that both their hyperprolactinemia and hypertension were controlled by bromocriptine, a dopamine agonist. They concluded that reduced central dopaminergic activity may be a factor in maintaining essential hypertension. We examined the serum prolactin and thyrotropin (TSH) responses to thyrotropin releasing hormone (TRH), metoclopramide (a dopamine antagonist) and bromocriptine in 10 normal and 10 hypertensive normoreninemic men. TRH caused significant increase of both prolactin and TSH and metoclopramide caused significant increase of prolactin in both normals and hypertensives. Bromocriptine suppressed prolactin and TSH significantly in both groups. There were no significant differences in prolactin and TSH levels between the normal and hypertensive groups before or during the tests. These results provide no support for the hypothesis that alterations in the activity of central dopaminergic neurons are involved in the maintenance of the elevated blood pressure of normoreninemic men with essential hypertension.