The neurosteroid allopregnanolone sulfate inhibits Na v 1.3 α subunit-containing voltage-gated sodium channels, expressed in Xenopus oocytes.

The neurosteroid allopregnanolone has potent analgesic effects, and its potential use for neuropathic pain is supported by recent reports. However, the analgesic mechanisms are obscure. The voltage-gated sodium channels (Nav ) α subunit Nav 1.3 is thought to play an essential role in neuropathic pain. Here, we report the effects of allopregnanolone sulfate (APAS) on sodium currents (INa ) in Xenopus oocytes expressing Nav 1.3 with β1 or β3 subunits. APAS suppressed INa of Nav 1.3 with β1 and β3 in a concentration-dependent manner (IC50 values; 75 and 26 μmol/L). These results suggest the possible importance of Nav 1.3 inhibition for the analgesic mechanisms of allopregnanolone.