Pressor and Hormonal Responses to Intravenous Injection of Metoclopramide in Normotensive and Hypertensive Patients

To assess the dopaminergic regulation of blood pressure and the renin-angiotensin-aldosterone system in fourteen essential hypertension (EHT) and six normotensives (NT), intravenous injections of 10 mg of the dopamine antagonist, metoclopramide (MCP), were given. Essential hypertension patients were divided into two subgroups according to the basal values of plasma renin activity (PRA). Plasma prolactin (PRL), aldosterone (ALDO), norepinephrine (NE) and epinephrine (E) in seven high-renin EHT revealed significantly higher basal values than normal- and low-renin EHT. Intravenous injections of MCP caused significant increases in PRL and ALDO but not in NE, E and PRA in all subjects. However, in high-renin EHT the responses of PRL and ALDO were significantly marked compared to other subjects. In spite of these hormonal changes after MCP, blood pressure was unaltered. The present data suggest that “tonic inhibition” of PRL and ALDO by the dopaminergic system is partially regulated by the renin-angiotensin system regardless of the levels of blood pressure.