The anticonvulsant retigabine suppresses neuronal K2-mediated currents.

Enhancement of neuronal M-currents, generated through K7.2-K7.5 channels, has gained much interest for its potential in developing treatments for hyperexcitability-related disorders such as epilepsy. Retigabine, a K7 channel opener, has proven to be an effective anticonvulsant and has recently also gained attention due to its neuroprotective properties. In the present study, we found that the auxiliary KCNE2 subunit reduced the K7.2-K7.3 retigabine sensitivity approximately 5-fold. In addition, using both mammalian expression systems and cultured hippocampal neurons we determined that low μM retigabine concentrations had 'off-target' effects on K2.1 channels which have recently been implicated in apoptosis. Clinical retigabine concentrations (0.3-3 μM) inhibited K2.1 channel function upon prolonged exposure. The suppression of the K2.1 conductance was only partially reversible. Our results identified K2.1 as a new molecular target for retigabine, thus giving a potential explanation for retigabine's neuroprotective properties.