We examined the preventive effect of metoclopramide on the development of esophageal varices in a rat model. Thirty rats were divided into three groups: metoclopramide (7.5 mg/kg twice a day, intraperitoneally), control group I (saline 2 ml/kg twice a day, intraperitoneally), and control group II (incised lower esophageal sphincter and metoclopramide 7.5 mg/kg twice a day, intraperitoneally). On the 14th postoperative day, lower esophageal sphincter pressure in the metoclopramide group (8.6±1.4 cm H2O) increased more than in the control groups (5.4±0.5, 5.0±0.5 cm H2O, P<0.01). Development of small collateral vessels from the spleen to the retroperitoneum was evident only in the metoclopramide group, as seen on the portography (P<0.01). Histologically, the variceal area of the horizontal cross section of the esophagus in the metoclopramide group (0.62±0.26 mm2)was significantly smaller than in the controls (2.67±0.95, 2.78±0.82 mm2), determined using an image processor-analyzer for photographing histological specimens (P<0.01). We also investigated the effect of metoclopramide on smooth muscle cells in the rat portal vein, using isometric-tension recording. Metoclopramide relaxed the smooth muscle precontracted with norepinephrine, in a concentration-dependent manner. Thus, metoclopramide inhibits the development of esophageal varices in this rat model due to both an increase in resistance of the lower esophagus and to development of small collaterals.
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