Analgesia Synergism of Essential Oil from Pericarp of Zanthoxylum schinifolium and Verapamil

Objective. To evaluate the synergistic analgesic effect of essential oil of Zanthoxylum schinifolium Sieb. et Zucc. (EOZ) and verapamil (Ver). Method. The qualitative and quantitative composition of EOZ were determined with gas chromatography/Mass spectrometer. The interaction between EOZ and Ver in antinociceptive activity was evaluated by using acetic acid-induced writhing, hot plate, and tail flick tests in mice and in isolated toad sciatic nerve test. Results. Linalool, limonene, and sabinene are the major components of EOZ. EOZ (middle-dose: 40 mg·kg(-1), high-dose: 80 mg·kg(-1)) and EOZ + Ver (Each dose group) have remarkable analgesic effects on pain in mice induced by acetic acid-induced writhing, hot plate, and tail flick tests. Low-dose EOZ (20 mg·kg(-1)) had no analgesic action, but when it is combined with Ver it has shown significant antinociception. Verapamil has a faint analgesic effect but was not able to inhibit action potential transmission in toad sciatic nerve. EOZ (0.2%) and EOZ + Ver (0.2% + 0.05%) also inhibited action potential transmission in toad sciatic nerve. Combination of EOZ with Ver had a greater analgesic effect and inhibition of nerve action potential transmission compared to its components EOZ and Ver. Conclusion. The combination of EOZ with Ver produces a synergistic analgesic effect.