Intracellular chloride activity of crayfish giant axons.
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Biomedical subjects
A Strickholm
Publications and source records attributed to A Strickholm.
A single electrode voltage, current- and patch-clamp amplifier with complete stable series resistance compensation.
An input headstage for single electrode voltage and current clamping is described which permits selecting desired operational modes during an experiment. These include cell attached or whole cell patch clamping, single micro-electrode voltage or current clamping, potential recording, iontophoresis and voltammetry. Input electrode series resistance with the electrode inserted in a cell or during whole cell patch clamping can be measured at any time. The unique circuitry allows complete compensation of the series resistance with high frequency response. The input series electrode resistance can also vary considerably around an initially set 100% compensation with intrinsic stability. An accelerator 'supercharger' or 'booster circuit' is included which can shorten the rise time of membrane potential to the command potential by a hundredfold. This improves the recording of early ion channel currents. Feedback resistors are selected remotely for the specific experimental need. Signal resolution in patch clamping is that expected from the thermal noise of the feedback resistor and electrode to membrane seal resistance. This headstage circuitry design thus allows interchangeable modes of operation and parameters during an experiment to obtain optimal conditions for signal detection and frequency response.
Electrodes↗
A supercharger for single electrode voltage and current clamping.
The theory and several circuits for supercharging is described for single micro and patch electrode voltage and current clamping. Supercharging is of use where the charging time of the cell membrane capacity results in the membrane potential change to considerably lag behind the command potential. This membrane capacity charging time is dependent on the series electrode resistance, the membrane resistance and capacity. Thus although amplifier voltage response times may be in microseconds, the membrane potential response to a step command potential often requires several milliseconds. Supercharging overcomes this difficulty by accelerating the membrane capacity charging time by applying a large initial and brief supercharging or 'booster' potential or current, to the command signal. Supercharging can improve membrane potential rise times by more than a hundred and thus bring membrane potentials to a stationary state well under a millisecond. Early changes in membrane properties are thus more readily observed during voltage and current clamping without being masked by capacitive currents. This technique also provides for the measurement of membrane time constants. The circuitry described is a simple add-on to the command signal pathway, is easy to adjust and provides the appropriate supercharging potentials for sequential step command signals of different amplitudes.
Electrodes↗