Abstract
Purpose: Nicotinic receptor agonists and muscarinic receptor agonists have been reported to produce antinociceptive effects. We hypothesized that acetylcholine receptor antagonists would decrease the pain threshold. The aim of the present study was to clarify this hypothesis with regard to drugs that are commonly used perioperatively: pancuronium, vecuronium, atropine, and scopolamine. Methods: Nociceptive effects of each drug were studied in ICR strain mice using hot-plate, acetic acid-writhing, and tail-pinch tests. Results: Hot-plate jumping latency was decreased by administration of pancuronium, but not by vecuronium. It was also decreased by higher doses of atropine and scopolamine. In the acetic acid-writhing test, four antagonists increased the frequency of writhing reactions. Conclusion: The present results suggest that antagonists of nicotinic and muscarinic receptors lower the pain threshold.
