Coles J A, Orkand R K, Yamate C L
Laboratoire d'Ophthalmologie Expèrimentale, Genève, Switzerland.
Glia. 1989;2(5):287-97. doi: 10.1002/glia.440020502.
Double-barrelled ion-selective microelectrodes were used to measure free [Cl-] in photoreceptors, extracellular space, and glial cells in superfused slices of drone retina. Tests indicated that with normal superfusate the intracellular electrode signal was due essentially to Cl- and not to some other interfering anion. The results indicate that Cl- is more concentrated in both photoreceptors and glial cells than would be predicted for a passive electrochemical distribution. When the photoreceptors were stimulated by a standard train of 20 ms flashes, 1/s for 90 s, their intracellular free [Cl-] (Cli) rose by 8 +/- 1 mM. At the end of stimulation Cli usually continued to rise for up to a further 2 min and then returned toward the baseline over about 10 min. During light stimulation Cli in the glia rose. The magnitude of the increase was 5.1 +/- 0.4 mM, about half the increase in Ki. In some extracellular recording sites, light stimulation caused [Cl-] to increase and in others to decrease. The mean change was -0.7 mM, SD 6.5 mM. The Cl- that entered the photoreceptors and the glia was presumably made available by the shrinking of the extracellular space. When the cells were depolarized by increasing [K+] in the superfusate from 7.5 mM to 18 mM, Cli increased. The half-time of the change in Cli was longer than the half-time of the depolarization by 10-30 s in the glia and 50-250s in the photoreceptors. During superfusion with 0 Cl- Ringer's solution, the light-induced rise in extracellular [K+] was greater by a factor of 1.4-2.7, and the clearance after the end of the stimulation was slower. The rate of increase in glial Ki during light stimulation fell; the rate of increase of glial Ki caused by superfusion with raised [K+] (in the absence of Cl-) fell more. We conclude that when extracellular [K+] is increased, entry of Cl- into the glia is necessary for part, but not all, of the net uptake of K+. During light stimulation, the observed movement of CL- into glia contributes to homeostasis of extracellular [K+], and the cell swelling associated with movement of Cl- into both glia and photoreceptors contributes to homeostasis of extracellular [Na+].
双管离子选择性微电极用于测量雄蜂视网膜灌流切片中光感受器、细胞外间隙和神经胶质细胞内的游离[Cl⁻]。测试表明，在正常灌流液条件下，细胞内电极信号主要归因于Cl⁻，而非其他干扰性阴离子。结果表明，Cl⁻在光感受器和神经胶质细胞中的浓度均高于被动电化学分布所预测的浓度。当用光强度为1/s、持续时间20 ms的标准闪光序列刺激光感受器90 s时，其细胞内游离[Cl⁻]（Cli）升高8±1 mM。刺激结束时，Cli通常会继续升高长达2分钟，然后在约10分钟内恢复至基线水平。在光刺激期间，神经胶质细胞中的Cli升高。升高幅度为5.1±0.4 mM，约为Ki升高幅度的一半。在一些细胞外记录位点，光刺激导致[Cl⁻]升高，而在其他位点则导致降低。平均变化为-0.7 mM，标准差为6.5 mM。进入光感受器和神经胶质细胞的Cl⁻可能是由于细胞外间隙缩小而释放出来的。当通过将灌流液中的[K⁺]从7.5 mM增加到18 mM使细胞去极化时，Cli升高。在神经胶质细胞中，Cli变化的半衰期比去极化的半衰期长10 - 30 s，在光感受器中长50 - 250 s。在用0 Cl⁻林格氏液灌流期间，光诱导的细胞外[K⁺]升高幅度增大1.4 - 2.7倍，刺激结束后的清除速度减慢。光刺激期间神经胶质细胞Ki的升高速率下降；用升高的[K⁺]（无Cl⁻）灌流引起的神经胶质细胞Ki升高速率下降得更多。我们得出结论，当细胞外[K⁺]升高时，Cl⁻进入神经胶质细胞对于部分（而非全部）K⁺的净摄取是必要的。在光刺激期间，观察到的Cl⁻进入神经胶质细胞的过程有助于细胞外[K⁺]的稳态，而与Cl⁻进入神经胶质细胞和光感受器相关的细胞肿胀有助于细胞外[Na⁺]的稳态。
