Antiallodynic Effect of Intrathecal Korean Red Ginseng in Cisplatin-Induced Neuropathic Pain Rats

Background: Chemotherapy-induced neuropathic pain (CINP) is a serious side effect of chemotherapy. Korean Red Ginseng (KRG) is a popular herbal medicine in Asian countries. We examined the therapeutic potential of intrathecally administered KRG for CINP and clarified the mechanisms of action with regard to 5-hydroxytryptamine (5-HT) 7 receptor at the spinal level. Methods: CINP was evoked by intraperitoneal injection of cisplatin in male Sprague-Dawley rats. After examining the effects of intrathecally administered KRG on CINP, 5-HT receptor antagonist (dihydroergocristine [DHE]) was pretreated to determine the involvement of 5-HT receptor. In addition, intrathecal 5-HT 7 receptor antagonist (SB269970) was administered to define the role of 5-HT 7 receptor on the effect of KRG. 5-HT 7 receptor mRNA expression levels and 5-HT concentrations were examined in the spinal cord. Results: Intrathecally administered KRG produced a limited, but a dose-dependent, antiallodynic effect. Intrathecally administered DHE antagonized the antiallodynia caused by KRG. Furthermore, intrathecal SB269970 also reversed the effect of KRG. No changes in 5-HT 7 receptor mRNA expression were seen in the dorsal horn of the spinal cord after cisplatin injection. After injecting cisplatin, 5-HT levels were decreased in the spinal cord, whereas those of 5-HT were increased by intrathecal KRG. Conclusions: Intrathecally administered KRG decreased CINP. In addition, spinal 5-HT 7 receptors contributed to the antiallodynic effect of KRG.