γ-Aminobutyric Acid (GABA) is contained in pancreatic islet β-cells although its physiological role in pancreatic exocrine function is completely unknown at the present time. Recently, we have reported that exogenous GABA enhances secretagogue-evoked exocrine secretion in the isolated, perfused rat pancreas. This study was aimed to investigate an effect of exogenous GABA on pancreatic exocrine secretion in vivo evoked by intestinal stimulation. Rats were anesthetized with urethane (1.4 g/kg) after 24-h fast with free access to water. GABA (10, 30 and 100μmol/kg/h), given intravenously, did not change spontaneous pancreatic amylase secretion but dose-dependently elevated the amylase secretion evoked by intraduodenal sodium oleate (0.05 mmol/h). GABA (30μmol/kg/h) also further increased the amylase secretion stimulated by CCK (30 pmol/kg/h) plus secretin (20 pmol/kg/h) but failed to modify the amylase secretion induced by secretin alone. GABA (10, 30 and 100μmol/kg/h) also dose-dependently elevated pancreatic amylase secretion evoked by CCK alone. Bicuculline (100μmol/kg/h), a GABAA-receptor antagonist, markedly reduced the GABA-enhanced pancreatic responses to sodium oleate, CCK plus secretin or CCK alone. The results indicate that GABA enhances the sodium oleate-evoked pancreatic amylase secretion via GABAA-receptors in anesthetized rats, which may account for elevating the action of CCK released by sodium oleate.