The International Journal of Neuropsychopharmacology

Research Article

The synergistic inhibitory actions of oxcarbazepine on voltage-gated sodium and potassium currents in differentiated NG108-15 neuronal cells and model neurons

Chin-Wei Huanga1a2, Chao-Ching Huanga2a3, Ming-Wei Lina4, Jing-Jane Tsaia1 and Sheng-Nan Wua4a5 c1

a1 Department of Neurology, National Cheng Kung University School of Medicine, Tainan, Taiwan

a2 Institute of Clinical Medicine, National Cheng Kung University School of Medicine, Tainan, Taiwan

a3 Department of Pediatrics, National Cheng Kung University School of Medicine, Tainan, Taiwan

a4 Institute of Basic Medicine, National Cheng Kung University School of Medicine, Tainan, Taiwan

a5 Department of Physiology, National Cheng Kung University School of Medicine, Tainan, Taiwan

Abstract

Oxcarbazepine (OXC), one of the newer anti-epileptic drugs, has been demonstrating its efficacy on wide-spectrum neuropsychiatric disorders. However, the ionic mechanism of OXC actions in neurons remains incompletely understood. With the aid of patch-clamp technology, we first investigated the effects of OXC on ion currents in NG108-15 neuronal cells differentiated with cyclic AMP. We found OXC (0.3–30 μm) caused a reversible reduction in the amplitude of voltage-gated Na+ current (INa). The IC50 value required for the inhibition of INa by OXC was 3.1 μm. OXC (3 μm) could shift the steady-state inactivation of INa to a more negative membrane potential by approximately −9 mV with no effect on the slope of the inactivation curve, and produce a significant prolongation in the recovery of INa inactivation. Additionally, OXC was effective in suppressing persistent INa (INa(P)) elicited by long ramp pulses. The blockade of INa by OXC does not simply reduce current magnitude, but alters current kinetics. Moreover, OXC could suppress the amplitude of delayed rectifier K+ current (IK(DR)), with no effect on M-type K+ current (IK(M)). In current-clamp configuration, OXC could reduce the amplitude of action potentials and prolong action-potential duration. Furthermore, the simulations, based on hippocampal pyramidal neurons (Pinsky–Rinzel model) and a network of the Hodgkin–Huxley model, were analysed to investigate the effect of OXC on action potentials. Taken together, our results suggest that the synergistic blocking effects on INa and IK(DR) may contribute to the underlying mechanisms through which OXC affects neuronal function in vivo.

(Received September 02 2007)

(Reviewed October 17 2007)

(Revised November 06 2007)

(Accepted November 15 2007)

(Online publication January 10 2008)

Correspondence:

c1 Address for correspondence: Dr Sheng-Nan Wu, Department of Physiology, National Cheng-Kung University Medical Center, No. 1, University Road, Tainan City, Taiwan. Tel.: 886-6-2353535-5334 (ext. 5334) Fax: 886-6-2362780 E-mail: snwu@mail.ncku.edu.tw