Experimental determination of Cm measurement related hardware parameters of the patch-clamp amplifier

Abstract

Accurate C m measurements rely on accurate determination of specific parameters of a patch-clamp amplifier (PCA). Hardware-related parameters, such as the resistance R f and the stray capacitance C f of the feedback resistor, the input capacitance C i, the injection capacitance C j, and the extra capacitances introduced by the BNC connector, are of significance in the sense of obtaining absolute estimates of cell parameters. In the present paper, a frequency-domain method, or the f-method for simplicity, is put forward to experimentally determine the actual values of basic circuit elements for our self-developed PCA. The f-method makes use of sine waves and amplitude/phase measurements instead of the square-wave responses to determine the above parameters of a PCA, and thereby calibrates the PAC for capacitance measurements. Experimental results prove that the f-method is excellent in determining hardware-related parameters, with 3–5% error of the impedance of the “10 MΩ setting”, and about 2% error of the impedance of the “model cell” of the model circuit for our PCA. The f-method enables us not only to picture components of fast capacitances, but also to guarantee complete fast capacitance compensation; it may be applicable for other PCAs.