Netzer R, Pflimlin P, Trube G
Pharma Division, F. Hoffmann-La Roche Ltd., Basel, Switzerland.
Pflugers Arch. 1994 Feb;426(3-4):206-13. doi: 10.1007/BF00374773.
The barium current through voltage-dependent calcium channels was recorded from cultured rat cortical neurons with the whole-cell configuration of the patch-clamp technique. The maximal current evoked by depolarising pulses from -80 mV to 0 mV was divided into inactivating and non-inactivating fractions. During the first minutes of whole-cell recording, the amplitude of the inactivating fraction increased from less than 0.1 nA to an average value of 1 nA, whereas the amplitude of the non-inactivating component remained essentially the same. This increase in amplitude was prevented when the "perforated-patch technique" was used, suggesting that some intracellular factor that inhibited the barium current was lost or destroyed during conventional whole-cell experiments. When GTP[gamma-S] or GTP was added to the pipette solution, no increase or only a weak rise of the inactivating current was seen, whereas GDP[beta-S] accelerated its increase. The results suggest that some of the calcium channels expressed in cultured cortical neurons are inhibited by a G protein even in the absence of added neurotransmitter. The current increase observed during whole-cell recordings may be due to a loss of intracellular GTP and the subsequent inactivation of an inhibitory G protein.
采用膜片钳技术的全细胞记录模式，记录培养的大鼠皮层神经元中通过电压依赖性钙通道的钡电流。从-80mV去极化到0mV的脉冲所诱发的最大电流被分为失活部分和非失活部分。在全细胞记录的最初几分钟内，失活部分的电流幅度从小于0.1nA增加到平均值1nA，而非失活部分的电流幅度基本保持不变。当使用“穿孔膜片技术”时，这种幅度增加被阻止，这表明在传统的全细胞实验中，一些抑制钡电流的细胞内因子丢失或被破坏。当向微电极溶液中加入GTP[γ-S]或GTP时，未观察到失活电流增加或仅有微弱增加，而GDP[β-S]加速了其增加。结果表明，即使在没有添加神经递质的情况下，培养的皮层神经元中表达的一些钙通道也受到G蛋白的抑制。在全细胞记录过程中观察到的电流增加可能是由于细胞内GTP的丢失以及随后抑制性G蛋白的失活所致。
