Although GABA is synthesized in pancreatic β-cells, its physiological role in pancreatic exocrine function is completely unknown at the present time. Very recently, we firstly reported that exogenous GABA enhanced pancreatic secretion stimulated by enzyme-secretagogues in the isolated, perfused rat pancreas. The present study was aimed to investigate whether GABA also exerts the enhancing effect on pancreatic secretion at the postprandial state in vivo. GABA, given intravenously at 30 μmol/kg/h, did not change spontaneous pancreatic secretion in anesthetized rats. However, GABA enhanced pancreatic secretions of fluid and amylase stimulated by intraduodenal infusion of sodium oleate. Because sodium oleate releases CCK and secretin, effects of GABA on pancreatic secretion stimulated by the petides were also examined. GABA did not modify the secretin-stimulated pancreatic secretions but further elevated the CCK-stimulated amylase secretion. In conclusion, GABA elevates the sodium oleate-stimulated pancreatic secretion by enhancing the action of CCK released by sodium oleate in anesthetized rats. The results indicate that GABA elevates pancreatic exocrine secretion at the postprandial state in rats.