甲基苯丙胺对瞬时外向钾电流影响

Effects of methamphetamine on transient outward K+ currents

目的观察甲基苯丙胺(Meth)对瞬时外向钾电流的影响及原因。方法将怀孕18 d SD大鼠胎鼠海马神经元分为对照组和Meth处理组,利用全细胞膜片钳方法记录外向瞬时钾电流变化;采用原位末端转移酶标记技术(TUNEL)观察Meth引起的细胞损伤作用;利用逆转录聚合酶链反应(RT-PCR)方法观察瞬时外向电流成分中Kv1.4、4.1、4.2和4.3表达,并通过western-blot方法观察Kv4.2蛋白表达。结果与对照组[(87.4±12.5)pA/pF]比较,Meth能引起瞬时外向钾电流增大[(120.1±19.6)pA/pF](P<0.01),与对照组(1.00±0.18)比较,Meth处理组凋亡率为对照组的(7.11±0.95)倍(P<0.01),钾通道抑制剂4-氨基吡啶(4-AP)明显抑制神经元凋亡(P<0.01);Kv4.2可能是外向电流成分中主要贡献者,Meth能上调Kv4.2通道蛋白表达;与Kv4.2上调密切相关的Kchip2/3、Kchip4、CaMK2蛋白表达增高。结论 Meth引起的瞬时钾电流增大可能通过Kv4.2上调来实现,但其机制仍需进一步探讨。

Objective To investigate the effects of methamphetamine（Meth） on the transient outward K＋ currents and its mechanisms.Methods Hippocampal neurons were harvested from 18-day-old embryonic rats and divided into control and Meth treated group.The currents were recorded with the whole cell patch clamp and the cell damage was detected by the TdT-mediated dUTP nick end labeling（TUNEL） assay.The mRNA expressions of Kv1.4,Kv4.1,Kv4.2,and Kv4.3 were evaluated by reverse transcription-PCR（RT-PCR）.Furthermore,the expression of Kv4.2 was detected with western-blot after the treatment of Meth.Results Meth significantly increased the transient outward K＋ currents（120.1±19.6 pA/pF,P0.01）compared with the control group（87.4±12.5 pA/pF） and caused neuronal damage（control group：1.00±0.18 vs Meth treated group：7.11±0.95,P0.01）.However,4-aminopyridine（4-AP）,the antagonist of the transient currents,substantially retarded the cell damage induced by Meth（4.96±1.32,P0.01）.Moreover,Kv4.2 might be the main contributor in transient currents.With western-blot assay,we observed that Meth up-regulated the Kv4.2 expression and the expressions of Kchip2/3,Kchip4,and CaMK2,which were closely associated with the expression of Kv4.2,were also up-regulated.Conclusion The up-regulation of Kv4.2 might be involved in Meth induced transient outward K＋ current increments,however,the mechanisms still need to be clarified.