Effect of cholecystokinin and secretin on contractile activity of isolated gastric muscle strips in guinea pigs

AIM:To study the effect of cholecystokinin-octapeptide (CCK-8) and secretin on contractile activity of isolated gastric muscle strips in guinea pigs.METHODS:Each isolated gastric muscle strip was suspended in a tissue chamber containing 5mL Krebs solution constantly warmed by water jacked at 37° and supplied with a mixed gas of 95% O(2) and 5% CO(2). After incubating for 1h under 1g tension, varied concentrations of CCK-8 and secretin were added respectively in the tissue chamber and the contractile response was measured isometrically on ink-writing recorders.RESULTS:CCK-8 could increase (1) all regional circular and longitudinal muscular tension at rest (fundus LM 19.7% ± 2.1%, P < 0.01; fundus CM 16.7% ± 2.2%, P < 0.01; gastric body LM 16.8% ± 2.3%, P < 0.01; body CM 12.7% ± 2.6%, P <0.01; antrum LM 12.3% ± 1.3%, P < 0.01; antrum CM 16.7% ± 4.5%, P < 0.01; pylous CM 12.7% ± 5.0%, P < 0.05);(2)contractile frequencies of body LM, both LM and CM of antrum and pylorus CM (5.1/min ± 0.2/min to 5.6/min ± 0.2/min, 5.9/min ± 0.2/min to 6.6/min ± 0.1/min, 5.4/min ± 0.3/min to 6.3/min ± 0.4/min, 1.3/min ± 0.2/min to 2.3/min ± 0.3/min, respectively, P < 0.05); the mean contractile amplitude of antral circular muscle (58.6% ± 18.4%, P < 0.05) and (3)the motility index of pylorus CM (145.0% ± 23.8%, P < 0.01), but decrease the mean contractile amplitude of gastric body and antral LM (-10.3% ± 3.3%, -10.5% ± 4.6%, respectively, P < 0.05 =. All the CCK-8 effects were not blocked by atropine or indomethacin. Secretin had no effect on gastric smooth muscle activity.CONCLUSION:CCK-8 possessed both excitatory and inhibitory action on contractile activity of different regions of stomach in guinea pigs. Its action was not mediated via cholinergic M receptor and endogenous prostaglandin receptor.