Brief calcium transients evoked by glutamate receptor agonists in rat dorsal horn neurons: fast kinetics and mechanisms.
Brief calcium transients evoked by glutamate receptor agonists in rat dorsal horn neurons: fast kinetics and mechanisms.
复制标题
大鼠背角神经元中谷氨酸受体激动剂引起的短暂钙瞬变：快速动力学和机制。
DOI：
10.1113/jphysiol.1993.sp019805
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发表时间：
1993
期刊：
影响因子：
--
通讯作者：
MacDermott,AB
中科院分区：
文献类型：
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作者：
Reichling,DB;MacDermott,AB
1. 钙指示剂indo‐1用于分析兴奋性氨基酸（EAA）刺激背角神经元引起的细胞内钙离子（[Ca2+]i）反应的受体特异性机制。在亚秒时间尺度上测量[Ca2+]i的染色体变化，在设计的条件下，允许膜电位介导激动剂门控通道和电压门控钙通道（VGCCs）之间的相互作用。2. 通过细胞外[K+]的升高，电压门控钙通道以受体独立的方式被激活。K（+）‐诱发的[Ca2+]i瞬态的浓度依赖性在细胞之间是陡峭的和可变的，平均最大[Ca2+]i响应为1400 nM，最大上升速率很快。这些数据表明，vgc为Ca2+的进入提供了一个高容量的途径，对膜电位的微小变化非常敏感。3. 使用非脱敏激动剂盐酸盐刺激非NMDA受体也引起了大的[Ca2+]i反应（平均840 nM），这主要是由于vgc的间接激活。然而，在测试的60%的神经元中，盐酸盐在浓度高于10微米时瞬时引起的[Ca2+]i成分不会被有效的VGCC阻滞剂镧（La3+）阻断。对盐酸盐的La（3+）‐抗性[Ca2+]i反应呈指数级上升，需要细胞外Ca2+，并且既不是由EAA递质的诱发释放引起的，也不是由Na（+）‐Ca2+交换的逆转引起的。这些反应可能是由非NMDA受体的Ca（2+）‐渗透性构象介导的，也可以由准质酸、(S)‐α‐氨基‐3‐羟基‐5‐甲基‐4‐异恶唑丙酸（AMPA）和谷氨酸引起。4. 非NMDA受体通过使用quisqualate或AMPA以脱敏方式激活。半qualate诱发了小的[Ca2+]i瞬态（210 nM），上升速率缓慢。通常，在3微米以上的准质量，反应的大小减小，反映了受体的脱敏。细胞外Ca2+的去除阻断了对准质酸的反应，这表明在大多数背角神经元中不会发生细胞内Ca2+储存的动员。然而，反式‐（+‐）‐1‐氨基‐1,3‐环戊烷二羧酸（反式‐ACPD）偶尔能够引起适度的Ca2+释放。5. Ca（2+）‐渗透性NMDA受体的激活可诱发[Ca2+]i瞬变（780 nM），具有中等的上升速率，并且通常在NMDA浓度约300微米时达到最大振幅。6. 谷氨酸被用来检测[Ca2+]i对内源性配体激活混合EAA受体亚型的反应。（摘要删节为400字）
1. The calcium indicator dye, indo‐1, was used to analyse the receptor‐specific mechanisms of intracellular calcium ion ([Ca2+]i) responses evoked by excitatory amino acid (EAA) stimulation of dorsal horn neurons. Measurements of somal changes in [Ca2+]i were made on a subsecond time scale under conditions designed to allow membrane potential to mediate interactions between agonist‐gated channels and voltage‐gated calcium channels (VGCCs). 2. Voltage‐gated calcium channels were activated in a receptor‐independent manner using elevated extracellular [K+]. The concentration‐dependence of K(+)‐evoked [Ca2+]i transients was steep and variable among cells, with a mean maximal [Ca2+]i response of 1400 nM and a rapid maximal rate of rise. These data indicate that VGCCs provide a high‐capacity route for Ca2+ entry that is very sensitive to small changes in membrane potential. 3. Stimulation of non‐NMDA receptors using the non‐desensitizing agonist kainate also evoked large [Ca2+]i responses (mean, 840 nM) that were predominantly due to indirect activation of VGCCs. However, in 60% of neurons tested, a component of the [Ca2+]i transient evoked by kainate at concentrations above 10 microM was not blocked by the potent VGCC blocker, lanthanum (La3+). The La(3+)‐resistant [Ca2+]i responses to kainate rose exponentially, required extracellular Ca2+, and were caused neither by evoked release of EAA transmitters nor by reversal of Na(+)‐Ca2+ exchange. These responses may be mediated by a Ca(2+)‐permeable conformation of non‐NMDA receptors and can also be evoked by quisqualate, (S)‐alpha‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole propionic acid (AMPA) and glutamate. 4. Non‐NMDA receptors were activated in a desensitizing manner using quisqualate or AMPA. Quisqualate evoked small [Ca2+]i transients (210 nM) with a slow rate of rise. Typically, above 3 microM quisqualate, the size of the responses decreased, reflecting desensitization of the receptor. Responses to quisqualate were blocked by removal of extracellular Ca2+ indicating that mobilization of intracellular Ca2+ stores does not occur in the majority of dorsal horn neurons. However, trans‐(+‐)‐1‐amino‐1,3‐cyclopentane dicarboxylic acid (trans‐ACPD) was occasionally able to evoke modest Ca2+ release. 5. Activation of the Ca(2+)‐permeable NMDA receptors evoked [Ca2+]i transients that were large (780 nM), with a moderate rate of rise, and that generally achieved a maximum amplitude at NMDA concentrations around 300 microM. 6. Glutamate was used to examine [Ca2+]i responses to the activation of mixed EAA receptor subtypes by an endogenous ligand.(ABSTRACT TRUNCATED AT 400 WORDS)