ACTION OF BRIEF PULSES OF GLUTAMATE ON AMPA KAINATE RECEPTORS IN PATCHES FROM DIFFERENT NEURONS OF RAT HIPPOCAMPAL SLICES
ACTION OF BRIEF PULSES OF GLUTAMATE ON AMPA KAINATE RECEPTORS IN PATCHES FROM DIFFERENT NEURONS OF RAT HIPPOCAMPAL SLICES
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DOI：
10.1113/jphysiol.1992.sp019417
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发表时间：
1992-12-01
影响因子：
5.5
通讯作者：
SAKMANN, B
中科院分区：
文献类型：
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作者：
COLQUHOUN, D;JONAS, P;SAKMANN, B
1.从大鼠海马脑片齿状回颗粒细胞和CA 3、CA 1区锥体细胞中分离出外向斑片。使用压电驱动的双管应用移液器将贴片短暂暴露于L-谷氨酸。应用程序的谷氨酸盐（1毫米）的1毫秒的持续时间激活补丁电流上升和衰减迅速。这些谷氨酸受体（GluR）介导的电流的20- 80%上升时间通常为0.2-0.6 ms，在-50 mV时，不同膜片的峰值电流在10 - 500 pA之间变化.对于来自三种细胞类型的贴片，ImM谷氨酸的短暂脉冲的峰值电流-电压关系在正常细胞外溶液中几乎是线性的（-100至60 mV）。对于所有三种细胞类型，在峰值处激活的GluR通道相对于K+对Ca 2+的渗透性小于0.1（在双离子条件下，Ca 2+在膜的细胞外侧，K+在膜的细胞内侧）。1 mM谷氨酸1 ms脉冲后电流的偏移衰减时间常数很短，齿状回、CA 3和CA 1细胞斑块的平均值分别为3.0 +/- 0.8、2.5 +/- 0.7和2.3 +/- 0.7 ms。偏移时间常数是独立的膜电位和独立的谷氨酸浓度（200 μ M和1 mM）的三种细胞类型。应用100 ms持续时间的1 mM谷氨酸盐表明谷氨酸盐反应迅速脱敏。对于齿状回、CA 3和CA 1细胞的斑片，脱敏的时间常数分别为9.4 +/- 2.7、11.3 +/- 2.8和9.3 +/- 2.8 ms。脱敏时间常数仅弱依赖于谷氨酸浓度（200 μ M和1 mM）的三种细胞类型。因此，对于两种谷氨酸浓度，偏移时间常数比脱敏时间常数快约四倍。谷氨酸盐的双脉冲应用表明，即使是ImM谷氨酸盐的Ims脉冲也会导致GluR通道的部分（约60%）脱敏。齿状回颗粒细胞斑的脱敏恢复时间比CA 3或CA 1锥体细胞斑慢.通过在1 mM谷氨酸的1 ms测试脉冲之前将贴片暴露于低谷氨酸浓度至少15 s，在平衡状态下研究脱敏。通过在CA 3和CA 1细胞斑中用9.6和4.2 μ M谷氨酸预平衡，测试脉冲的峰值幅度减半：齿状回颗粒细胞斑中的GluR通道相当敏感，峰值幅度减半的浓度（IC 50）为2.4 μ M。选择性AMPA/红藻氨酸（KA）受体拮抗剂6-氰基-7-硝基喹喔啉-2，3-二酮（CNQX）可阻断1 mM谷氨酸的1 ms脉冲激活的电流。IC 50值在106至183 nM.10的范围内，由1 mM谷氨酸的1 ms脉冲激活的电流在许多方面类似于兴奋性突触后电流（EPSC），表明在兴奋性突触传递期间，该递质仅短暂存在于突触间隙中。脱敏可能是由一个单一的EPSC，以及低环境谷氨酸浓度。脱敏的细胞特异性差异可能影响三突触海马回路中突触传递的功效。
1. Outside-out patches were isolated from granule cells of dentate gyrus and pyramidal cells of CA3 and CA1 regions of rat hippocampal slices. Patches were exposed briefly to L-glutamate using a piezo-driven double-barrelled application pipette.2. Applications of glutamate (1 mM) of 1 ms duration activated patch currents which rose and decayed rapidly. The 20-80 % rise time of these glutamate receptor (GluR)-mediated currents was usually 0.2-0.6 ms. At -50 mV the peak current varied from 10 to 500 pA in different patches.3. The peak current-voltage relation for brief pulses of 1 mM glutamate was virtually linear in normal extracellular solution for patches from the three cell types (-100 to 60 mV).4. The permeability of GluR channels activated at the peak to Ca2+, relative to K+, was less than 0.1 for all three cell types (under bi-ionic conditions with Ca2+ on the extracellular side and K+ on the intracellular side of the membrane).5. The offset decay time constant of the current following 1 ms pulses of 1 mM glutamate was brief, with mean values of 3.0 +/- 0.8, 2.5 +/- 0.7, and 2.3 +/- 0.7 ms for dentate, CA3 and CA1 cell patches, respectively. Offset time constants were independent of membrane potential and independent of glutamate concentration (200 muM and 1 mM) for the three cell types.6. Applications of 1 mM glutamate of 100 ms duration showed that glutamate responses desensitized rapidly. The time constants for desensitization were 9.4 +/- 2.7, 11.3 +/- 2.8, and 9.3 +/- 2.8 ms for patches from dentate, CA3 and CA1 cells respectively. Desensitization time constants were only weakly dependent on glutamate concentration (200 muM and 1 mM) for the three cell types. Thus offset time constants are about four times faster than desensitization time constants for both glutamate concentrations.7. Double pulse application of glutamate indicated that even a 1 ms pulse of 1 mM glutamate causes partial (about 60%) desensitization of GluR channels. The time course of recovery from desensitization was slower in dentate gyrus granule cell patches than in CA3 or CA1 pyramidal cell patches.8. Desensitization was studied at equilibrium by exposing patches to low glutamate concentrations for at least 15 s before a 1 ms test pulse of 1 mM glutamate. The peak amplitude of the test pulse was halved by pre-equilibration with 9.6 and 4.2 muM glutamate in CA3 and CA1 cell patches: GluR channels in dentate gyrus granule cell patches were rather more sensitive, the concentration which halves the peak amplitude (IC50) being 2.4 muM.9. Currents activated by 1 ms pulses of 1 mM glutamate were blocked by the selective AMPA/kainate (KA) receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). The IC50 values were in the range 106 to 183 nM.10, The currents activated by 1 ms pulses of 1 mM glutamate resembled excitatory postsynaptic currents (EPSCs) in many ways, suggesting that the transmitter is present only briefly in the synpatic cleft during excitatory synaptic transmission. Desensitization may be caused by a single EPSC, as well as by low ambient glutamate concentrations. Cell-specific differences in desensitization may influence the efficacy of synaptic transmission in the trisynaptic hippocampal circuit.