Quetiapine reverses paclitaxel-induced neuropathic pain in mice: Role of alpha2- adrenergic receptors.

Objectives: Paclitaxel-induced peripheral neuropathy is a common adverse effect of cancer chemo -therapy. This neuropathy has a profound impact on quality of life and patient's survival. Preventing and treating paclitaxel-induced peripheral neuropathy is a major concern. First- and second-generation antipsychotics have shown analgesic effects both in humans and animals. Quetiapine is a novel atypical antipsychotic with low propensity to induce extrapyramidal or hyperprolactinemia side effects. The present study was designed to investigate the effects of quetiapine on the development and expression of neuropathic pain induced by paclitaxel in mice and the role of α ₂ -adrenoceptors on its antinociception.
Materials and Methods: Paclitaxel (2 mg/kg IP) was injected for five consecutive days which resulted in thermal hyperalgesia and mechanical and cold allodynia.
Results: Early administration of quetiapine from the 1 ^st day until the 5 ^th day (5, 10, and 15 mg/kg PO) did not affect thermal, mechanical, and cold stimuli and could not prevent the development of neuropathic pain. In contrast, when quetiapine (10 and 15 mg/kg PO) administration was started on the 6 ^th day after the first paclitaxel injections, once the model had been established, and given daily until the 10 ^th day, heat hyperalgesia and mechanical and cold allodynia were significantly attenuated. Also, the effect of quetiapine on heat hyperalgesia was reversed by pretreatment with yohimbine, as an alpha-2 adrenergic receptor antagonist.
Conclusion: These results indicate that quetiapine, when administered after nerve injury can reverse the expression of neuropathic pain. Also, we conclude that α _2- adrenoceptors participate in the antinociceptive effects of quetiapine.