The Characterization Of The Effect Resulted From The Combination Of Stimulatory And Inhibitory Agents On The Gastrointestinal Smooth Muscle Contractility

Background and Purpose: This study is designed to examine whether presence of the law of bidirectional regulation resulting from the effect of the paired used of one stimulatory and one inhibitory agent on the contractilities of gastric and intestinal smooth muscle.Methods: In this in vitro experiment, the strips of gastric and intestinal smooth muscle were selected in the assay, and the contractility of these smooth muscle strips was chosen as the index. The contractility in high and low states for these isolated gastric and intestinal smooth muscle strips were achieved by adjusting he concentration of K+ in the Krebs'solution. Four drug combinations were tested on the high and low contractile states of both gastric and intestinal smooth muscle.Results:â‘ The contractility of rat gastric and intestinal smooth muscle strips was relative low in the low K+ solution.â‘¡The contractility of rat gastric and intestinal smooth muscle strips was relative high in the high K+ solution.â‘¢The inhibitory effect on both gastric and intestinal smooth muscle contractility was observed by using aminophylline and isoprenaline respectively.â‘£The stimulatory effect on both gastric and intestinal smooth muscle contractility was observed by using histamine,acetylcholine,and neostigmine respectively. We found that for low contractile state of both gastric and intestinal smooth muscle strips, the stimulatory effect was observed by using the combination of histamine-aminophylline, neosti- gmine-isoprenaline, acetylcholine-aminophylline, histamine- isoprenaline and these combinations promote the contraction of both gastric and intestinal smooth muscle in high contractile state.Discussion: The significances resulting from the above bidirectional regulation are as follows: (1) The bidirectional regulation results from the different combination which has different mechanisms suggests presence the law of bidirectional in the smooth muscle. (2) These paired drug combinations may help to reduce drug side effects. (3) The combination of stimulatory and inhibitory agent makes smooth muscle contraction is neither over contacted nor over relaxed, suggesting a possible way to ease the smooth muscle dysfunction.