科研之友
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摘要
Neurotransmitters affect the membrane potential (V-m) of target cells by modulating the activity of receptor-linked ion channels. The direction and amplitude of the resulting transmembrane current depend on the resting level of V-m and the gradient across the membrane of permeant ion species. V-m, in addition, governs the activation state of voltage-gated channels. Knowledge of the exact level of V-m is therefore crucial to evaluate the nature of the neurotransmitter effect. However, the traditional methods to measure V-m, with microelectrodes or the whole-cell current-clamp technique, have the drawback that the recording pipette is in contact with the cytoplasm, and dialysis with the pipette solution alters the ionic composition of the interior of the cell. Here we describe a novel technique to determine the V-m of an intact cell from the reversal potential of K+ currents through a cell-attached patch, Applying the method to interneurons in hippocampal brain slices yielded more negative values for V-m than subsequent whole-cell current-clamp measurements from the same cell, presumably reflecting the development of a Donnan potential between cytoplasm and pipette solution in the whole-cell mode. Cell-attached V-m measurements were used to study GABAergic actions in intact CA1 interneurons. In 1- to 3-week-old rats, bath-applied GABA inhibited these cells by stabilizing V-m at a level depending on contributions from both GABA(A) and GABA(B) components. In contrast, in 1- to 4-d-old animals, only GABA(A) receptors were activated resulting in a depolarizing GABA response.
- 出版日期1999-4-1
