AIM: To investigate the effect of long-lasting somatostatin analogue octreotide (Oct) injected into the third cerebral ventricle (TCV) on gastric acid secretion in rats.METHODS: TCVs were cannulated in male Wistar rats anesthetized with sodium pentobarbital. One week later acute gastric lumen perfusion was carried out and gastric acid was continuously washed with 37℃ saline by a perfusion pump. Gastric perfusion samples were collected every 10 min and titrated by 0.01 moL/L NaOH to neutral. On the basis of subcutaneous (sc) injection of pentagastrin (G-5, 160 μg/kg), Oct (0.025 μg, 0.05 μg,0.1 μg, n= 12 in each group) or vehicle (pyrogen-free physiological saline, n = 10) was injected into the TCV.Before and after the TCV injection, 1 h total acid output (TAO) was determined and experimental data were expressed in change rate (%) of TAO.RESULTS: Oct (0.025, 0.05 and 0.1 μg) injected into the TCV resulted in change rate of 1.56% (P＞0.05),20.21% (P＜ 0.01) and 37.82% of TAO (P＜ 0.001),respectively. Moreover, comparison in change rate of TAO among these 3 doses showed P＜ 0.05 between 0.025μg and 0.05 μg, P＜ 0.01 between 0.025 μg and 0.1μg,and P＜ 0.05 between 0.05μg and 0.1 μg. However, sc injection of 0.05 μg Oct had no effect on G-5 stimulated gastric acid secretion.CONCLUSION: Octreotide injected into the third cerebral ventricle inhibits gastrin-induced gastric acid secretion in a dose-dependent manner.