Subcellular Ca2+ Mobilization in Gastric Smooth Muscle Contraction

Background: The stomach can be generally classified anatomically into three parts; fundus, corpus, and antrum. It has not been well demonstrated how the three regions contribute to specified gastric motility. In the present study, the regional differences on contractile response and intracellular levels ([) were investigated in a mouse gastric muscle. Methods: An isometrical contraction was measured with a computerized phyiograph, and [ was measured with fura-PE3/AM, a fluorescent indicator in gastric smooth muscle from mice. Results: Carbachol (CCh), a potent muscarinic receptor agonist, generated rhythmic contractions in a dose dependent manner, superimposed on tonic components in th antral muscle. Whereas similar contractile responses to CCh was obtained in the antrum, CCh evoked tonic components predominantly. Ch increased [ in a dose dependent manner in both the antral and fundic smooth muscle. However, the increment of [ in the fundus was greater than that of the antrum. Verapamil (M), a 1-type channel blocker, inhibited completely the contraction and [ induced by CCh in the antral strips, whereas the responses in the fundus showed a resistance to verapamil. Conclusions: These results suggest that muscainic stimulation has a regional difference on muscle contractility and [, which is mediated by differences of movement in mouse gastric muscle.