Cross talk between the vanilloid and cholinergic receptors in guinea pig ileum. is capsaicin a partial cholinergic agonist
Adebayo Tawo Jolayemi
Department of Anaesthesia, Portland District Hospital, Portland City, Victoria, Australia
Aim: The activity of Capsaicin in Guinea Pig ileum was investigated and compared to the effects of Acetylcholine.
Methods: Tubular segments (3-4 cm) from distal ileum of Dunkin-Hartley guinea-pigs (n=12) weighing 300'450g of either sex were suspended under standard physiological state in 30-ml Two-Chambered Organ Baths in two parallel, control and study groups. Incremental doses of either Capsaicin alone or with Acetylcholine or Atropine were added to the bath-fluid and washed out three-to-five times after the maximum responses of the tissues were attained. Concentrations of Capsaicin (and other drugs used) were repeated where appropriate at regular intervals of 20'30 minutes after the last washing. Capsaicin (and other drugs-) induced contractions and responses of the isolated ileal muscle preparations were recorded isometrically by means of force displacement transducers, 2-Channel "Gemini" Recorder, and pen-recording microdynamometers (model 7070).
Results: There was a concentration-dependent increase in the basal tone and the contracted guinea pig isolated ileal muscle preparations by Capsaicin (5-150 ug/ml) which was inhibited by atropine at P<0.02. The contraction of the ileum by acetylcholine was in turn inhibited by Capsaicin at (P<0.05).
Conclusion: Capsaicin has biphasic effects on smooth muscles of the GIT. There is a cross talk between the vanilloid and cholinergic receptors. Further work needs to be done to elucidate the perioperative uses of this interaction.
Reference:
- Herbert, M.K., Holzer, P., and Roewer, N. (editors-1999) Problems of the Gastrointestinal Tract in Anesthesia, the Perioperative Period, and Intensive Care. Springer, Berlin, Germany.
- Rang, H. P., Urban, L. (1995) New molecules in analgesia British Journal of Anaesthesia; 75: 145-156.
