[The reactivity of canine colonic and ileal smooth muscle to carbachol (Jestryl)].

Experiments were carried out on longitudinal and circular smooth-muscle strips isolated from the ileum and colon of healthy dogs (controls) and of dogs with local peritonitis. The changes in the contractile responses of the strips to carbachol administered cumulatively were studied, and the EC50 and pD2 values were calculated from the dose-response curves. For the colonic longitudinal strips the EC50 was 6 x 10(-8)M and the pD2 was 7.58. The pD2 for the ileal longitudinal strips was 7.83. The pD2 value for the circular strips from the ileum and colon was 7.19 and 8.87 respectively. In the dogs with local peritonitis, the sensitivity of the longitudinal strips to carbachol was higher (the pD2 for the ileum was 7.86 and for the colon-7.21) as compared to the circular strips (the pD2 for the ileum was 6.22 and for the colon-6.65). The affinity of the cholinoreceptors in the ileal circular strips to carbachol was decreased as compared to controls.