Mechanism of delayed gastric emptying in naturally occurring CCK-A receptor gene knockout (OLETF) rats

We recently found a specific strain of rats (OLETF rats) in which CCK-A rec eptor gene expression is lacking because of a genetic abnormality. As delay ed gastric emptying has been reported in this strain, we examined its mecha nism. A liquid gastric load containing phenol red was administered using an orogastric tube into the stomach in OLETF and control (LETO) rats. The sto mach was removed 0, 15, 30 and 45 min after meal ingestion and the content of phenol red was measured to estimate the rate of gastric emptying. Pretre atment of reserpine enhanced gastric emptying in both strains. A tenfold do se of reserpine was required in OLETF rats to induce a similar effect to LE TO rats. The plasma noradrenalin level was significantly higher in OLETF th an LETO rats, When the smooth muscle of the stomach was isolated and contra ction in vitro was examined, the smooth muscle functions were not deteriora ted in OLETF rats. The thickness of muscle determined by hematoxylineosin s taining was not different between strains. It is suggested that the delayed gastric emptying in OLETF rats may be due to increased sympathetic nerve f unction.