Characterization of cannabinoid-induced relief of neuropathic pain in a rat model of cisplatin-induced neuropathy
Clinical use of antineoplastic drugs is associated with the development of numerous adverse effects that many patients find intolerable, including peripheral neuropathy. Cannabinoids have relieved neuropathic pain in different animal models. But their therapeutic activities could be affected by their psychoactive properties. The aim of this work was to determine the effect of cannabinoids in cisplatin-evoked neuropathy. For this purpose, the non-selective agonist WIN55,212-2 (WIN), the CB1-selective agonist ACEA or the CB2-selective agonist JWH133 (or their vehicle)was either systemically administered at a non-psychoactive dose or locally injected in cisplatin-treated rats. Selective CB1 and CB2 cannabinoid antagonists (AM251 and SR144528, respectively)were used to characterize cannabinoid effects. Cisplatin-treated rats showed mechanical allodynia but not thermal hyperalgesia. Cannabinoid agonists alleviated mechanical allodynia. This effect was mediated by both CB1 and CB2 cannabinoid receptors when the cannabinoid was systemically applied. At the dose used, cannabinoid agonists had no psychoactive effect. The local effect of the drug involved the activation of peripheral CB1 receptors whereas involvement of CB2 receptors was less clear. In a rat model of cisplatin-induced neuropathy, cannabinoids have an antinociceptive effect, but the cannabinoid receptors involved could be different depending on the route of administration. Non-psychoactive doses of cannabinoid agonists are capable of alleviating the signs of peripheral neuropathy when systemically applied. Interestingly, local administration of selective CB1 agonists or systemic administration of CB2 agonists, which are non-psychoactive, may serve as new therapeutic alternatives for symptom management in painful neuropathy associated with cisplatin treatment.