Effect of Agonist and Antagonist on the In Vitro Contractility of Inflamed Vermiform Appendix

Introduction: Appendicitis poses a great health problem worldwide. Previous studies demonstrated structural damage to neuronal network and interstitial cell of Cajal in appendicitis. Above observations suggest for the alterations in appendicular motility/contractility in appendicitis. But the mechanisms involved in mediating the contractility in inflamed vermiform appendix is not known till date.

Aim: The present in vitro study was performed to find out the mechanisms responsible for contractility in the inflamed human vermiform appendix.

Materials And Methods: Contractions of the longitudinal muscle strips of inflamed appendix were recorded in vitro at 37±0.5°C. Control contractions were recorded for 30 min after an initial tension of 0.5 gram. Initially dose-response experiments of agonists (acetylcholine, serotonin and histamine) were performed separately and the dose that produced maximum contraction was determined with each agonist. This maximal dose of agonist was used to elicit contractions in next series of experiments before and after pre-treatment with appropriate antagonists like atropine, ondansetron (5-HT antagonist) and chlorpheniramine maleate respectively.

Results: Acetylcholine (ACh) and serotonin (5-HT) elicited maximum amplitude of contraction at 10 µM and 1 µM concentration respectively. These contractions were significantly blocked by prior exposure of muscle strips with atropine (100 µM) and ondansetron (10 µM). Histamine produced very low amplitude of contractions in comparison to ACh or 5-HT and did not exhibit dose-response relations. The histamine induced contractions were blocked by H antagonist chlorpheniramine maleate (100 µM).

Conclusion: The observations suggested that the contractility of longitudinal muscle strips of inflamed vermiform appendix in human beings was predominantly mediated by muscarinic and serotonergic (5-HT) mechanisms, whereas, histaminergic mechanisms played a minor role in mediating the contractility.