Metoclopramide decreases baroreflex sensitivity in patients with essential hypertension

The effect of metoclopramide (10 mg, iv.) or physiological saline on the exercise-induced (standardized bicycle ergometry) increase in blood pressure and heart rate of patients with essential hypertension was investigated in a double blind, randomized, self controlled study. Metoclopramide had no effect on the exercise-induced increase in blood pressure but significantly enhanced the tachycardia due to ergometry after 4-6 min exercise. The mean slope of linear regression lines calculated from the systolic blood pressure and the corresponding heart rate measured before and during (at 1,2,3,4,5 min) exercise after metoclopramide was significantly steeper than after physiological saline (1.1 +/- 0.12 vs 0.79 +/- 0.09; mean +/- SEM), indicating the decrease in baroreflex sensitivity after metoclopramide. On the basis of results the possible role of endogenous dopaminergic mechanisms in suppressing some components of pressor effect of physical exercise can be hypothesized.