RT Journal Article
SR Electronic
T1 Noninvasive Measurements of the Membrane Potential and GABAergic Action in Hippocampal Interneurons
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 2546
OP 2555
DO 10.1523/JNEUROSCI.19-07-02546.1999
VO 19
IS 7
A1 Jos A. H. Verheugen
A1 Desdemona Fricker
A1 Richard Miles
YR 1999
UL http://www.jneurosci.org/content/19/7/2546.abstract
AB Neurotransmitters affect the membrane potential (Vm) 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 Vm and the gradient across the membrane of permeant ion species. Vm, in addition, governs the activation state of voltage-gated channels. Knowledge of the exact level of Vm is therefore crucial to evaluate the nature of the neurotransmitter effect. However, the traditional methods to measureVm, 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 theVm 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 Vm 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-attachedVm 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 stabilizingVm at a level depending on contributions from both GABAA and GABAB components. In contrast, in 1- to 4-d-old animals, only GABAA receptors were activated resulting in a depolarizing GABA response.