Patch-clamp studies of glutamate receptor channels in cultured hippocampal neurons.

人们普遍认为谷氨酸是哺乳动物中枢神经系统中介导兴奋性突触传递的主要神经递质。此外，越来越多的证据表明，谷氨酸引起的细胞事件在诱导突触传递有效性的可塑性变化中发挥关键作用。因此，阐明谷氨酸和相关兴奋性氨基酸(EAAS)对中枢神经元膜性质的影响是非常重要的。在这项研究中，我们检测了EaS激活的大鼠海马神经元受体通道的特性。膜片钳技术的全细胞和外向结构被用来研究宏观电流和单通道电流。主要研究结果如下：1.谷氨酸受体通道的离子有Na~(++)、K~(++)和Ca~(2+)~(2+)。谷氨酸以40-50 ps和20 ps的单通道电导激活多个不同水平的单通道事件。The…较大(40-50pS)和较小(&lt；20pS)的事件分别是由于N-甲基-D-天冬氨酸(NMDA)和非NMDA(Quisqualate，或Kainate)受体的激活。胞外液中的镁离子在-40 mV.4以上的电位范围内可明显抑制NMDA通道的开放。NMDA受体通道对Ca~(2+)和Gt~(2+)具有高通透性。根据恒定场方程，P&lt；ca&gt；/P&lt；na&gt；值为6.2。NMDA通道在二价阳离子中的通透性顺序为：Ba^&lt；2+&gt；(1.2)&gt；Ca^&lt；2+&gt；(1.0)&gt；sr^&lt；2+&gt；(0.8)&gt；Mn^&lt；2+&gt；(0.3)&gt；奎宁酸是一种兴奋性脑代谢产物，选择性地激活NMDA受体通道。红藻氨酸受体通道分为两类。1型受体的钙离子通透性很低。而2型受体对钙离子的通透性相对较高(P_&lt；Ca&gt；/P_&lt；NA&gt；=2.3)。需要对2型红藻氨酸受体的单通道特性进行研究。较少

It is widely accepted that glutamate is the principal neurotransmitter that mediates excitatory synaptic transmission in the mammalian central nervous system. Furthermore, evidence is accumulating that cellular events caused by glutamate play a key role in the induction of plastic changes in the efficacy of the synaptic transmission. Therefore it is important to clarify changes in the membrane properties induced by glutamate and related excitatory amino acids (EAAS) in the central neurons. In this study, we examined the properties of receptor channels activated by EAAs in cultured rat hippocampal neurons. The whole-cell and outside-out configurations of the patch-clamp technique were used to study macroscopic and single-channel currents. The results are summarized as follows:1. The ions permeant through glutamate receptor channels are Na^+, K^+ and Ca^<2+>.2. Glutamate activated single channel events of several different levels with single-channel conductances 40-50 pS and < 20 pS. The … More large (40-50 pS) and small (< 20 pS) events were due to the activation of N-methyl-D-aspartate (NMDA) and non-NMDA (quisqualate, or kainate) receptors, respectively.3. Mg^<21> in the extracellular solution markedly suppressed the opening of NMDA channels in the potential range more negative than -40 mV.4. The NMDA receptor channel was highly permeable to Ca^<2+>. The value Of P_<ca>/P_<na> was 6.2 according to the constant field equation. The permsability sequence of the NMDA channel among the divalent cations was determined to be Ba^<2+>(1.2) > Ca^<2+>(1.0) > Sr^<2+>(0.8) > Mn^<2+>(O.3)>> Mg^<2+>(<O.02).5. Quinolinate, an excitotoxic brain metabolite, selectively activated NMDA receptor channels.6. Kainate receptor channels were classified into two types. The Ca^<2+> permeability of the type 1 receptor was very low. In contrast, the type 2 receptor showed relatively high permeability to Ca^<2+> (P_<ca>/P_<na>=2.3). Study is needed to characterize single-channel properties of the type 2 kainate receptor. Less