Evidence for dopamine as an inhibitor of vasoprotein release in man.

The effect of dopamine on vasopressin release was studied by the infusion of L-Dopa, a dopamine precursor that crosses the blood-brain barrier. L-Dopa suppressed resting levels of vasopressin and inhibited the rise of vasopressin produced by head-up tilt. Carbidopa, a decarboxylase inhibitor that does not cross the blood-brain barrier blocked the action of L-Dopa. These results suggest that dopamine inhibits the release of vasopressin, either by an action at pituitary level or at the median eminence of the hypothalamus.