Duloxetine-induced inhibition of voltage-gated K+ 3.1 (Kv3.1) channels and underlying electrophysiological mechanisms.

Duloxetine is a serotonin-norepinephrine reuptake inhibitor that has been widely used to treat major depression; however, it has also been associated with severe neuropsychiatric side effects, including hallucinations, confusion, and suicide attempts. Nevertheless, the electrophysiological mechanisms underlying these adverse effects remain poorly understood. In this study, we investigated the effect of duloxetine on cloned neuronal rat voltage-gated K+ (Kv) channel subunit Kv3.1, stably expressed in Chinese hamster ovary (CHO) cells. Duloxetine inhibited the Kv3.1 current in a concentration-dependent manner with a half-maximal inhibitory concentration (IC50) of 2.04 ± 0.27 μM (approximately 5-fold higher than the peak therapeutic plasma concentration of 0.4 μM) and a Hill coefficient of 0.94 ± 0.08. This inhibitory effect was associated with accelerated current inactivation. The association and dissociation rate constants for duloxetine were 43.43 ± 4.57 μM-1·s-1 and 122.12 ± 68.2 s-1, respectively. In addition, duloxetine shifted the voltage dependence of Kv3.1 steady-state inactivation toward a more negative direction and led to use-dependent inhibition upon repetitive stimulation (1 and 2 Hz). Duloxetine also slowed recovery from inactivation. Docking analysis predicted that duloxetine binds to the central pore and interface between the voltage-sensing and pore domains on Kv3.1 channel, supporting the inhibitory mechanisms of duloxetine. Furthermore, duloxetine inhibited Kv3.1-mediated currents in SH-SY5Y human neuroblastoma cells. Taken together, our results indicate that duloxetine inhibits Kv3.1 expressed in CHO cells in concentration-, time-, and use (open and inactivated states)-dependent manners, independently of its anti-depressive effects.