The traditional Japanese (Kampo) medicines yokukansan (YKS) and yokukansankachimpihange (YKSCH) have similar formulas and the same indications. In animals or cultured cells, the neuropharmacological actions of YKS are sometimes more beneficial than those of YKSCH. Since both drugs are used to treat sleep disorders in Japan, we examined the ameliorative effects of YKS and YKSCH on circadian rhythm disturbance and compared their efficacy using a mouse model of circadian rhythm disruption. Ramelteon was used as the positive control. Ramelteon treatment significantly reversed decreased running wheel activity during the advanced dark phase, indicating facilitation of circadian adaptation. YKS treatment also reversed the activity in the early period of drug treatment; however, it was not statistically significant. YKSCH treatment significantly reversed the decreased activity during the advanced dark phase. Plasma melatonin (MT) levels were significantly increased in the YKSCH but not in the YKS group. The ameliorative effect of YKSCH on rhythm disruption was significantly inhibited by coadministration of the MT2 receptor antagonist. Therefore, the therapeutic effect of YKSCH on circadian rhythm disruption would be attributable, to elevated endogenous MT levels. Taken together, YKS and YKSCH have different pharmacological properties and may be more precisely prescribed depending on patients' psychological symptoms.
Keywords: CH3/HeN mouse; Circadian rhythm; Melatonin; Running wheel activity; Yokukansan; Yokukansankachimpihange.
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