Effects of Mirogabalin, a Novel Ligand for the α₂δ Subunit of Voltage-gated Calcium Channels, on N-type Calcium Channel Currents of Rat Dorsal Root Ganglion Culture Neurons

Mirogabalin, which is a novel ligand for the α₂δ subunit of voltage-gated calcium channels, is being developed for treating neuropathic pain including diabetic peripheral neuropathy and postherpetic neuralgia. Mirogabalin possesses unique α₂δ subunit binding characteristics and has potent and long-lasting analgesic effects in neuropathic pain models. In the present study, we investigated the effects of mirogabalin on N-type calcium channel currents of the rat dorsal root ganglion (DRG) culture neurons using the whole-cell patch clamp technique. Small or medium DRG neurons were isolated from Sprague-Dawley rats and were incubated for 20 to 24 h with mirogabalin or pregabalin. The DRG neurons were depolarised from a holding potential of -40 mV to +40 mV in steps of 10 mV for 220 ms, and elicited N-type calcium channel currents were recorded. The N-type calcium channel currents were verified by sensitivity to ω-conotoxin GVIA, a selective N-type calcium channel blocker. Mirogabalin inhibited the calcium channel currents of rat DRG neurons at 50 μM, and pregabalin inhibited them at 200 μM. Mirogabalin and pregabalin showed significant differences in the peak current densities at depolarisation to -20 and -10 mV when compared with that shown by the vehicle control. In conclusion, mirogabalin inhibits N-type calcium channel currents in rat DRG culture neurons. The potent and long-lasting analgesic effects of mirogabalin are thought to be associated with its potent and selective binding to α₂δ-1 subunits and following functional inhibition of calcium channel currents.