α9-Containing Nicotinic Acetylcholine Receptors Are Required for RgIA-5474 Attenuation of Chemotherapy-Induced Neuropathic Pain

Nicotinic acetylcholine receptors containing the alpha 9 subunit have been mechanistically implicated in alleviating chemotherapy-induced neuropathic pain. However, the cell types that underlie these effects are currently unknown. RgIA-5474 is a recently developed, synthetic alpha-conotoxin analog that is a potent antagonist of human alpha 9 alpha 10 nAChRs. We used germline alpha 9 subunit knockout mice, CD3+ T-cell depletion, and conditional knockdown of the alpha 9 subunit in immune cells to examine the role of alpha 9-containing nAChRs that mediate RgIA-5474 alleviation of oxaliplatin-induced neuropathic pain. RgIA-5474 potently and selectively blocked mouse alpha 9 alpha 10 nAChRs. A one-time oxaliplatin injection resulted in cold allodynia that was reversed by RgIA-5474 administration in the wild type but not in alpha 9 germline knockout mice. RgIA-5474 also failed to produce analgesia in CD3+ T-cell-depleted male and female animals. Conditional knockdown of the alpha 9 subunit in immune cells of mice by the CreloxP system also eliminated the therapeutic effects of RgIA-5474 in both male and female mice. These results indicate that the alpha 9 nAChR subunit is necessary for the analgesic effects of RgIA-5474 and implicate alpha 9-containing nAChRs in immune cells as a nonopioid target for treating neuropathic pain.