Oxaliplatin, a platinum-based chemotherapy drug, often induces acute neuropathic pain, especially cold allodynia, even after a single administration. Subcutaneous injection of diluted bee venom (BV) into acupoints has been used to treat various pain symptoms in traditional oriental medicine. Although we previously demonstrated the suppressive effect of BV injection on oxaliplatin-induced cold allodynia in rats, its neurochemical mechanism remained unclear. This study investigates whether and how the cholinergic system mediates the relieving effect of BV injection on cold allodynia in oxaliplatin-administered rats. The behavioral signs of cold allodynia induced by an oxaliplatin administration (6 mg/kg, intraperitoneally (i.p.)) were evaluated by a tail immersion test in cold water (4°C). BV (0.25 mg/kg, subcutaneously (s.c.)) injection into the Yaoyangguan acupoint, located between the spinous processes of the fourth and fifth lumbar vertebrae, significantly alleviated the cold allodynia. This relieving effect of BV injection on oxaliplatin-induced cold allodynia was blocked by a pretreatment with mecamylamine (a non-selective nicotinic receptor antagonist, 2 mg/kg, i.p.), but not by atropine (a non-selective muscarinic receptor antagonist, 1 mg/kg, i.p.). Further, dihydro-β-erythroidinehydrobromide (DHβE, an α4β2 nicotinic antagonist, 5 mg/kg, i.p.) prevented the antiallodynic effect of BV, whereas methyllycaconitine (an α7 nicotinic antagonist, 6 mg/kg, i.p.) did not. Finally, intrathecal administration of DHβE (10 nM) blocked the BV-induced anti-allodynic effect. These results suggest that nicotinic acetylcholine receptors, especially spinal α4β2 receptors, but not muscarinic receptors, mediate the suppressive effect of BV injection on oxaliplatin-induced acute cold allodynia in rats.Key words oxaliplatin; bee venom; cholinergic; cold allodynia; nicotinic receptor; rat Oxaliplatin is a third-generation platinum-based chemotherapy drug for advanced colorectal cancer.1) Unlike the other platinum compounds (e.g. cisplatin and carboplatin), oxaliplatin does not induce nephrotoxicity and hepatotoxicity, but often induces a very acute painful neuropathy soon after an administration.2) This acute neuropathy is the only major dose-limiting toxicity associated with oxaliplatin use 3) and is characterized by the rapid onset of cold-induced peripheral dysesthesia, paresthesia, or hypoesthesia of the hands, feet, or throat. 4,5) Previous animal studies also have shown that a single administration of oxaliplatin (6 mg/kg, intraperitoneally (i.p.)) reproduces the neurotoxic profile, especially cold allodynia.6,7) However, its mechanism is still unclear and an effective treatment of established neuropathic cold allodynia remains to be found.
8)A subcutaneous injection of diluted bee venom (BV) into acupoints, so called 'bee venom acupuncture,' has been used as a part of traditional oriental medicine to relieve pain and treat various diseases, such as arthritis, rheumatism, cancer, asthma and skin diseases.9-11) It is a kind...