Inflammatory responses mediated by activated microglia play a pivotal role in the pathogenesis of human immunodeficiency virus type 1 (HIV-1)-associated neurocognitive disorders. Studies on identification of specific targets to control microglia activation and resultant neurotoxic activity are imperative. Increasing evidence indicate that voltage-gated K(+) (K(v)) channels are involved in the regulation of microglia functionality. In this study, we investigated K(v)1.3 channels in the regulation of neurotoxic activity mediated by HIV-1 glycoprotein 120 (gp120)-stimulated rat microglia. Our results showed treatment of microglia with gp120 increased the expression levels of K(v)1.3 mRNA and protein. In parallel, whole-cell patch-clamp studies revealed that gp120 enhanced microglia K(v)1.3 current, which was blocked by margatoxin, a K(v)1.3 blocker. The association of gp120 enhancement of K(v)1.3 current with microglia neurotoxicity was demonstrated by experimental results that blocking microglia K(v)1.3 attenuated gp120-associated microglia production of neurotoxins and neurotoxicity. Knockdown of K(v)1.3 gene by transfection of microglia with K(v)1.3-siRNA abrogated gp120-associated microglia neurotoxic activity. Further investigation unraveled an involvement of p38 MAPK in gp120 enhancement of microglia K(v)1.3 expression and resultant neurotoxic activity. These results suggest not only a role K(v)1.3 may have in gp120-associated microglia neurotoxic activity, but also a potential target for the development of therapeutic strategies.