AIM: To investigate the hypothesis that duodenal bulb (DB) inhibition on pyloric antrum (PA) contraction is reflex. METHODS: Balloon (condom)-tipped tube was introduced into 1st duodenum (DD) and a manometric tube into each of PA and DD. Duodenal and antral pressure response to duodenal and then PA balloon distension with saline was recorded. These tests were repeated after separate anesthetization of DD and PA. RESULTS: Two and 4 mL of 1st DD balloon distension produced no pressure changes in DD or PA (10.7 ± 1.2 vs 9.8 ± 1.2, 11.2 ± 1.2 vs 11.3 ± 1.2 on H2O respectively, P > 0.05). Six mL distension effected 1st DD pressure rise (30.6 ± 3.4 cm H2O, P < 0.01) and PA pressure decrease (6.2 ± 1.4 cm H2O, P < 0.05); no response in 2nd, 3rd and 4th DD. There was no difference between 6, 8, and 10 mL distensions. Ten mL PA distension produced no PA or 1st DD pressure changes (P > 0.05). Twenty mL distension increased PA pressure (92.4 ± 10.7 cm H2O, P < 0.01) and decreased 1st DD pressure (1.6 ± 0.3 cm H2O, P < 0.01); 30, 40, and 50 mL distension produced the same effect as the 20 mL distension (P > 0.05). PA or DD distension after separate anesthetization produced no significant pressure changes in PA or DD. CONCLUSION: Large volume DD distension produced DD pressure rise denoting DD contraction and PA pressure decline denoting PA relaxation. PA relaxation upon DD contraction is postulated to be mediated through a reflex which we call duodeno-antral reflex. Meanwhile, PA distension effected DD relaxation which we suggest to be reflex and termed antro-duodenal reflex. It is suggested that these 2 reflexes, could act as investigative tools indiagnosis of gastroduodenal motility disorders. AIM: To investigate the hypothesis that duodenal bulb (DB) inhibition on pyloric antrum (PA) contraction is reflex. METHODS: Balloon (condom) -tipped tube was introduced into 1st duodenum (DD) and a manometric tube into each of PA and DD . Duodenal and antral pressure response to duodenal and then PA balloon distension with saline was recorded. These tests were repeated after separate anesthetization of DD and PA. RESULTS: Two and 4 mL of 1st DD balloon distension produced no pressure changes in DD or PA 10.7 ± 1.2 vs 9.8 ± 1.2, 11.2 ± 1.2 vs 11.3 ± 1.2 on H2O respectively, P> 0.05). Six mL distension effect 1st DD pressure rise (30.6 ± 3.4 cm H2O, P <0.01) and PA pressure decrease (6.2 ± No effect in 2nd, 3rd and 4th DD. There was no difference between 6, 8, and 10 mL distensions. Ten mL PA distension produced no PA or 1st DD pressure changes (P> 0.05) Twenty mL distension increased PA pressure (92.4 ± 10.7 cm H2O, P <0.01) and decreased first DD pr PA or DD distension produced after the separate anesthetization produced no significant pressure changes in PA (P <0.01); 30, 40, and 50 mL distension produced the same effect as the 20 mL distension or DD. CONCLUSION: Large volume DD distension produced DD pressure rise denoting DD contraction and PA pressure decline denoting PA relaxation. PA relaxation upon DD contraction is postulated to be mediated through a reflex which we call duodeno-antral reflex. Meanwhile, PA distension effected DD relaxation which we suggest to be reflex and termed antro-duodenal reflex. It is suggested that these 2 reflexes, could act as investigative tools indiagnosis of gastroduodenal motility disorders.