Noise analysis of the glutamate-activated current in photoreceptors.
Noise analysis of the glutamate-activated current in photoreceptors.
复制标题
光感受器中谷氨酸激活电流的噪声分析。
DOI：
10.1016/s0006-3495(96)79613-3
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Lecar,H
中科院分区：
文献类型：
--
作者：
Larsson,HP;Picaud,SA;Werblin,FS;Lecar,H
光感受器中的谷氨酸激活电流归因于钠/谷氨酸转运体和谷氨酸激活的氯离子通道。我们利用全细胞膜片钳记录的噪声分析进一步研究了虎蝾螈单个、分离光感受器中的谷氨酸激活电流。在锥体中，电流由氯离子通道产生，其单通道电导为0.7 pS，开启寿命为2.4 ms。每个单元的通道数在10,000-20,000之间。通道的激活需要谷氨酸和钠的存在。单通道电导和通道的开放寿命与谷氨酸和钠的外部浓度无关。外部谷氨酸和钠只影响通道的打开速率。D， l -三o-3-羟基天冬氨酸（THA），一种谷氨酸运输阻滞剂，被证明是该通道的部分激动剂。无论是谷氨酸还是THA作为配体，单通道电导都是相同的，但THA作为配体时，通道的开放寿命仅为0.8 ms。在棒中，谷氨酸激活电流具有类似的单通道电导（0.74 pS）和打开寿命（3 ms）。我们提出了一个与这些结果一致的动力学模型，来解释转运蛋白如何同时作为钠/谷氨酸门控氯通道和谷氨酸/钠共转运蛋白。
The glutamate-activated current in photoreceptors has been attributed both to a sodium/glutamate transporter and to a glutamate-activated chloride channel. We have further studied the glutamate-activated current in single, isolated photoreceptors from the tiger salamander using noise analysis on whole-cell patch-clamp recordings. In cones, the current is generated by chloride channels with a single-channel conductance of 0.7 pS and an open lifetime of 2.4 ms. The number of channels per cell is in the range of 10,000–20,000. Activation of the channels requires the presence of both glutamate and sodium. The single-channel conductance and the open lifetime of the channel are independent of the external concentration of glutamate and sodium. External glutamate and sodium affect only the opening rate of the channels. D,L-Threo-3-hydroxyaspartate (THA), a glutamate-transport blocker, is shown to be a partial agonist for the channel. The single-channel conductance is the same regardless of whether glutamate or THA is the ligand, but the open lifetime of the channel is only 0.8 ms with THA as ligand. The glutamate-activated current in rods has a similar single-channel conductance (0.74 pS) and open lifetime (3 ms). We propose a kinetic model, consistent with these results, to explain how a transporter can simultaneously act both as a sodium/glutamate-gated chloride channel and a glutamate/sodium cotransporter.