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Measurement of cell impedance in frequency domain using discontinuous current clamp and white-noise-modulated current
M Weckström1, E Kouvalainen, M Juusola
1Department of Physiology, University of Oulu, Finland.
Abstract:
A method is described for the determination of cellular input impedance of non-spiking neurones. The input impedance is important when cellular geometry and the effects of voltage-dependent channels are considered. Cells are impaled with a single glass microelectrod and current is injected using a time-sharing technique. The cell's impedance is measured by randomly modulating the injected current and calculating the impedance as a transfer function between current and recorded membrane voltage. Corresponding coherence functions can also be calculated for estimating the signal-to-noise ratio, and also linearity (i.e. possible activation of voltage-dependent conductances) of the membrane.