Abstract
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[γ-S] or GTP was added to the pipette solution, no increase or only a weak rise of the inactivating current was seen, whereas GDP[β-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.
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Netzer, R., Pflimlin, P. & Trube, G. Tonic inhibition of neuronal calcium channels by G proteins removed during whole-cell patch-clamp experiments. Pflügers Arch. 426, 206–213 (1994). https://doi.org/10.1007/BF00374773
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DOI: https://doi.org/10.1007/BF00374773