Regional Differences in Motor Responsivenes to Hyoscine Butylbromide in Rabbit Isolated Small and Large Intestine

The effect of hyoscine butylbromide (scopolamine butylbromide), a competitive nonselective antagonist of acetylcholine at muscarinic receptors, on the isolated rabbit duodenum, ileum and colon was investigated. Hyoscine butylbromide (9×10M 9×10M) decreased in a concentration-dependent manner the amplitude of the spontaneous pendular movements of the rabbi-isolated duodenum (r=0.99; p<0.001), ileum (r=1; p<0.001) and colon (r=0.98; p<0.001). Hyoscine butylbromide decreased the tone of the spontaneous pendular movements. The effect on the tone of the duodenum was not concentration-dependent. It decreased the tone of the duodenum by 20.67% ± 5.99 (r=0.69; p>0.05); (F=1.38; p>0.05) and had no significant effect on the ileal tone. However, the tone of distal colon was decreased in a concentration-dependent manner (r=0.98; p<0.001).The frequency of the pendular movements was the least sensitive to hyoscine butylbromide. The frequency of duodenal and ileal contraction did not change. However, the frequency of pendular movements of the colon was slightly, but concentration-dependently (r=0.93; p<0.01) decreased. It is concluded that hyoscine butylbromide reduced the amplitudes of pendular movements most effectively in all parts of the intestines. The inhibitory effect on the tone was most pronounced on the colonic contractions, whereas the duodenal tone was less sensitive, and the ileal tone was unaffected. Only the frequency of the pendular movements of the rabbit colon was sensitive to the muscarinic blockade. It is suggested that hyoscine butylbromide predominantly acted on M1 muscarinic receptors.