Inhibition of NMDA-gated ion channels by bis(7)-tacrine: Whole-cell and single-channel studies

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• 作者：Yu-Wei Liu ; Jia-Lie Luo ; Hong Ren ; Robert W. Peoples ; Yong-Xun Ai ; Li-Jiang Liu ; Yuan-Ping Pang ; Zhi-Wang Li ; Yi-Fan Han ; Chao-Ying Li
• 关键词：Glutamate receptor ; NMDA receptor ; Acetylcholinesterase inhibitor ; Electrophysiology
• 刊名：Neuropharmacology
• 出版年：2008
• 期刊代码：33_00283908
• 类别：pha
• 出版时间：June 2008
• 卷：54
• 期：7
• 页码：1086-1094
• 文件大小：923 K

摘要

Bis(7)-tacrine is a novel dimeric acetylcholinesterase inhibitor derived from tacrine, and has been proposed as a promising agent to treat Alzheimer's disease. We have recently reported that bis(7)-tacrine prevents glutamate-induced neuronal apoptosis by antagonizing NMDA receptors. The purpose of this study was to characterize bis(7)-tacrine inhibition of NMDA-activated current by using patch-clamp recording techniques. In cultured rat hippocampal neurons, bis(7)-tacrine inhibited NMDA-activated whole-cell current in a concentration-dependent manner with an IC₅₀ of 0.66 ± 0.07 μM. Bis(7)-tacrine produced a gradual decline of NMDA-activated current to a steady-state, but this was not an indication of use-dependence. Also, the slow onset of inhibition by bis(7)-tacrine was not apparently due to an action at an intracellular site. Bis(7)-tacrine, 0.5 μM, decreased the maximal response to NMDA by 40%without changing its EC₅₀. Bis(7)-tacrine inhibition of NMDA-activated current was not voltage-dependent, and was independent of glycine concentration. Results of single-channel experiments obtained from cells expressing NR1 and NR2A subunits revealed that bis(7)-tacrine decreased the open probability and frequency of channel opening, but did not significantly alter the mean open time or introduce rapid closures. These results suggest that bis(7)-tacrine can inhibit NMDA receptor function in a manner that is slow in onset and offset and noncompetitive with respect to both NMDA and glycine. The noncompetitive inhibition of NMDA receptors by bis(7)-tacrine could contribute to its protective effect against glutamate-induced neurotoxicity.