Concomitant facilitation of GABAA receptors and KV7 channels by the non-opioid analgesic flupirtine

BACKGROUND AND PURPOSE Flupirtine is a non-opioid analgesic that has been in clinical use for more than 20 years. It is characterized as a selective neuronal potassium channel opener (SNEPCO). Nevertheless, its mechanisms of action remain controversial and are the purpose of this study. EXPERIMENTAL APPROACH Effects of flupirtine on native and recombinant voltage- and ligand-gated ion channels were explored in patch-clamp experiments using the following experimental systems: recombinant KIR3 and KV7 channels and a3 beta 4 nicotinic acetylcholine receptors expressed in tsA 201 cells; native voltage-gated Na+, Ca2+, inward rectifier K+, KV7 K+, and TRPV1 channels, as well as GABAA, glycine, and ionotropic glutamate receptors expressed in rat dorsal root ganglion, dorsal horn and hippocampal neurons. KEY RESULTS Therapeutic flupirtine concentrations (=10 mu M) did not affect voltage-gated Na+ or Ca2+ channels, inward rectifier K+ channels, nicotinic acetylcholine receptors, glycine or ionotropic glutamate receptors. Flupirtine shifted the gating of KV7 K+ channels to more negative potentials and the gating of GABAA receptors to lower GABA concentrations. These latter effects were more pronounced in dorsal root ganglion and dorsal horn neurons than in hippocampal neurons. In dorsal root ganglion and dorsal horn neurons, the facilitatory effect of therapeutic flupirtine concentrations on KV7 channels and GABAA receptors was comparable, whereas in hippocampal neurons the effects on KV7 channels were more pronounced. CONCLUSIONS AND IMPLICATIONS These results indicate that flupirtine exerts its analgesic action by acting on both GABAA receptors and KV7 channels.