Dopaminergic control of gastric mucosal blood flow in humans

We studied the dopaminergic regulation of the gastric mucosal blood flow (GMBF) measured with an endoscopic laser Doppler flowmetry in 27 healthy volunteers. They were randomly assigned to receive an endoscopic gastric submucosal injection (0.5 ml) of physiological saline (control group,N=10), 50 g of dopamine (DA) hydrochloride (N=8), and 500 g of a DA antagonist, metoclopramide (MCP) (N=9). The drugs were dissolved in the same saline volume (0.5 ml) as used in control group and were injected via the mucosal area where the baseline GMBF was measured and the postdose GMBF was monitored until 5 min postdose. There was no significant difference in the mean (±sem) baseline laser Doppler signals among the control, DA, and MCP groups (92.6±9.3, 81.8±9.0 and 96.9±13.3 mV, respectively). In the control group, no significant postdose changes in the laser Doppler signals occurred until 5 min postinjection. In contrast, the DA group exhibited a significant (P<0.05 or 0.01) increase in the laser Doppler signals at 2, 3, 4, and 5 min postdose (118.9±18.8, 128.5±16.9, 146.6±18.6, and 131.2±14.2 mV, respectively), whereas the MCP group exhibited a significant (P<0.05 or 0.01) decrease in the signals at 4 and 5 min postdose (67.9±5.3 and 64.8±3.5 mV, respectively), as compared not only with the respective baseline values but also with those obtained from other two groups at the corresponding postinjection periods. There was a significant (P<0.001) and negative correlation (r=–0.94) between the predose laser Doppler signals and their corresponding postinjection changes in the MCP group. Our data suggest that a tonic, dopaminergic stimulation may play a role in maintaining the GMBF in humansin vivo.This study was supported by grant-in-aids from the Ministry of Human Health and Welfare, Tokyo, and from the Pathophysiology Research Institute, Tokyo.