ISSN:
1432-2013
Keywords:
Microelectrode techniques
;
High-frequency microelectrode recording
;
Intracellular impedance measurements
;
Negative capacitance amplifiers
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract The fabrication of a new glass microelectrode for high-speed recording is reported. It consists of a Ling-Gerard microelectrode which is slit into a “spacer” capillary with the tip slightly protruding. Except for the ultimate tip (of ∼30 μm length) the entire assembly is coated with silver and insulated. After proper insertion into the cell the electrode provides a shield, which extends from the surface of the cell membrane up to the input of the amplifier. This electrode has two advantages: 1. it eliminates all capacitive pickup of bath potentials which is of paramount importance in impedance measurements and 2. if used in conjunction with negative capacitance amplifiers, it allows more faithful high-frequency recordings, than was possible with the conventional techniques, because the capacitance neutralization can be properly set even though the non-ideal transmission properties of the electrode tips are not known. Test experiments using a rapid amplifier circuit of own design show that the electrode assembly allows error-free phaseshift measurements of up to 30 kHz to be obtained with electrodes of 20 MΩ or risetimes (10–90%) of squarewave pulses of 10 to 12 μs. The corresponding time constants of 5 to 6 μs indicate that the time resolution of the new technique is superior to the apparent time resolution of the conventional techniques.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00584447
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