Inhibition of compound action potentials in the frog sciatic nerve by inchinkoto, a traditional Japanese medicine used for oral mucositis

Abstract

ObjectiveThis study aimed to determine the effects of traditional Japanese (Kampo) medicines used to treat oral mucositis on nerve conduction. MethodsThe effects of Kampo medicines, crude drugs, and chemical compounds on compound action potentials (CAPs) were analyzed using extracellular recordings in frog sciatic nerves. ResultsAmong the Kampo medicines, inchinkoto demonstrated the most significant reduction in CAP amplitude, with a half-maximal inhibitory concentration (IC50) of 5.4 mg/mL. Hangeshashinto, shosaikoto, hochuekkito, and juzentaihoto also showed a significant reduction. Regarding inchinkoto, Artemisiae Capillari Spica (artemisia) was the most effective crude drug, with an IC50 of 4.2 mg/mL for CAP amplitude reduction, whereas Gardeniae Fructus (gardenia) exerted no significant effect. However, the combined use of artemisia and gardenia reduced the CAP amplitude more effectively than artemisia alone, indicating a synergistic interaction. The chemical ingredient eugenol from artemisia administered at 1 and 3 mmol/L reduced CAP amplitude, whereas other chemical ingredients administered at 0.1 and 1 mmol/L had no significant effects. ConclusionsInchinkoto exhibited the most effective reduction in CAP amplitude in the sciatic nerve of frogs, primarily through the action of artemisia, with potential synergistic interaction between artemisia and gardenia.