Redox modulation of fast inactivation has been described in certain cloned A-type voltage-gated K(+) (Kv) channels in expressing systems, but the effects remain to be demonstrated in native neurons. In this study, we examined the effects of cysteine-specific redox agents on the A-type K(+) currents in acutely dissociated small diameter dorsal root ganglion (DRG) neurons from rats. The fast inactivation of most A-type currents was markedly removed or slowed by the oxidizing agents 2,2'-dithio-bis(5-nitropyridine) (DTBNP) and chloramine-T. Dithiothreitol, a reducing agent for the disulfide bond, restored the inactivation. These results demonstrated that native A-type K(+) channels, probably Kv1.4, could switch the roles between inactivating and non-inactivating K(+) channels via redox regulation in pain-sensing DRG neurons. The A-type channels may play a role in adjusting pain sensitivity in response to peripheral redox conditions.