Effect of ginsenosides, active components of ginseng, on capsaicin-inducedpain-related behavior

Our recent study demonstrated that ginsenosides had antinociceptive effects by reducing some types of pain-related behavior in mice (Yoon et al., 1998 . Ginsenosides induce differential antinociception and inhibit substance P- induced nociceptive response in mice. Life Science 62, PL319-PL325). In the present study we further investigated whether ginsenosides produce antinoc iceptive effects through an action at central or peripheral site(s) and whe ther these effects are mediated by the opioid system. Intraperitoneally inj ected ginsenosides suppressed in a dose-dependent manner the pain-related b ehavior produced by capsaicin injection into the plantar surface of the hin d paw; the ED50 was 49 mg/kg [26-92 mg/kg, 95% confidence interval (C.I.)]. Intrathecally or intracerebroventricularly administered ginsenosides also suppressed the capsaicin-induced pain-related behavior in a dose-dependent manner; the ED(50)s were 1.72 mg/kg (0.8-3.72 mg/kg, 95% C.I.) and 1.48 mg/ kg (0.8-2.6 mg/kg, 95% C.I.), respectively. On the other hand, subcutaneous ly injected ginsenosides to the plantar surface prior to the capsaicin inje ction did not alter the pain-related behavior. Naloxone pretreatment was wi thout effect in blocking the antinociceptive effect of intrathecally admini stered ginsenosides. Intraperitoneally injected ginsenosides also did not s ignificantly affect the motor response of animals. These results suggest th at ginsenosides produce antinociceptive effects through their action at the spinal and/or supraspinal site(s), not at nociceptors in the periphery. In addition, the results suggest that the antinociceptive effects are not med iated by opioid receptors. (C) 2000 Elsevier Science Ltd. All rights reserv ed.