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Evidence-Based Complementary and Alternative Medicine
Volume 2013, Article ID 413092, 10 pages
http://dx.doi.org/10.1155/2013/413092
Research Article

Saikosaponin a Enhances Transient Inactivating Potassium Current in Rat Hippocampal CA1 Neurons

1Department of Traditional Chinese Medicine, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, China
2School of Traditional Chinese Medicine, Southern Medical University, Guangzhou, Guangdong 510515, China
3Department of Traditional Chinese Medicine, Xijing Hospital, Fourth Military Medical University, Xi’an, Shanxi 710032, China
4Intensive Care Unit, Guang Zhou Municipal Hospital of Chinese Medicine, Guangzhou, Guangdong 510130, China
5Department of Traditional Chinese Medicine, Guang Zhou Brain Hospital, Guangzhou, Guangdong 510170, China
6Institute of Neuroscience, Fourth Military Medical University, Xi’an, Shanxi 710032, China

Received 16 November 2012; Accepted 1 January 2013

Academic Editor: Ke Liu

Copyright © 2013 Wei Xie et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Saikosaponin a (SSa), a main constituent of the Chinese herb Bupleurum chinense DC., has been demonstrated to have antiepileptic activity. Recent studies have shown that SSa could inhibit NMDA receptor current and persistent sodium current. However, the effects of SSa on potassium (K+) currents remain unclear. In this study, we tested the effect of SSa on 4AP-induced epileptiform discharges and K+ currents in CA1 neurons of rat hippocampal slices. We found that SSa significantly inhibited epileptiform discharges frequency and duration in hippocampal CA1 neurons in the 4AP seizure model in a dose-dependent manner with an of 0.7 μM. SSa effectively increased the amplitude of and , significantly negative-shifted the activation curve, and positive-shifted steady-state curve of . However, SSa induced no significant changes in the amplitude and activation curve of . In addition, SSa significantly increased the amplitude of 4AP-sensitive K+ current, while there was no significant change in the amplitude of TEA-sensitive K+ current. Together, our data indicate that SSa inhibits epileptiform discharges induced by 4AP in a dose-dependent manner and that SSa exerts selectively enhancing effects on . These increases in may contribute to the anticonvulsant mechanisms of SSa.