Mirogabalin activates the descending noradrenergic system by binding to the αδ-1 subunit of voltage-gated Ca channels to generate analgesic effects.

Gabapentinoids such as gabapentin and pregabalin, which bind specifically to the αδ subunit of voltage-gated Ca channels, are used for first-line treatment of neuropathic pain. Here, we examined the analgesic effect of mirogabalin besilate (referred to simply as mirogabalin), a novel gabapentinoid, focusing on its action on the spinal cord and the descending noradrenergic pain inhibitory system. When administered systemically (10 and 30 mg/kg, intraperitoneally (i.p.)) and locally (10 and 30 μg, intracerebroventricularly (i.c.v.) or intrathecally (i.t.)) to mice, mirogabalin was found to exert analgesic effects on thermal (plantar test) and mechanical (von Frey test) hypersensitivity developing after partial sciatic nerve ligation. Notably, its analgesic effects (30 mg/kg, i.p. and 30 μg, i.c.v.) disappeared in mice pretreated with yohimbine hydrochloride (3 μg, i.t.). Moreover, in mice harboring a mutation in the αδ-1 subunit resulting in substitution of arginine at position 217 with alanine to prevent gabapentinoid binding (R217A mutant mice), the analgesic effects of pregabalin and mirogabalin (30 μg, i.c.v., respectively) on mechanical hypersensitivity were almost completely suppressed. These results clearly demonstrate that mirogabalin also operates via the descending noradrenergic system, and that binding to the αδ-1 subunit supraspinally is essential for the pain relief effect of gabapentinoids.