Glass microelectrode tip capacitance: Its measurement and a method for its reduction

doi:10.1016/0165-0270(81)90057-1

Journal of Neuroscience Methods

Volume 3, Issue 3, February 1981, Pages 225-232

https://doi.org/10.1016/0165-0270(81)90057-1 Get rights and content

Abstract

The frequency response of input amplifiers used for measurement of bioelectric signals from small cells is severely limited by the resistance and capacitance of the fine glass microelectrodes which are required for these measurements. A significant improvement in the frequency response can be realized by employing the technique of input capacitance neutralization. This capacitance neutralization, however, is incomplete since: (1) the bandwidth of the input amplifier is finite; and (2) a fraction of the electrode capacitance is isolated from the amplifier input by a part of the electrode resistance and cannot be compensated. It is therefore desirable to ensure that the electrode capacitance is as low as possible before neutralization. A method is discussed for measuring and predicting the distributed capacitance of the microelectrode and a technique is described for coating the outside of the electrode near the tip with a substance which can lower the electrode capacitance per unit length by as much as 7-fold. The significance of the improved frequency response of the input amplifier that this technique provides is discussed in light of recent advances in intracellular single electrode voltage clamp technique.

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A simple and rapid method for improving recording characteristics using multibarrelled micropipettes
1992, Journal of Neuroscience Methods
A method for the simple and rapid fabrication of multibarrelled micropipettes with improved signal-to-noise characteristics is described. The process of silicone coating the exterior of the multibarrel assembly was found to improve recording characteristics greatly and to reduce recording noise during the passage of ionophoretic current. This simple process of fabrication and silicone coating is completed within 15–20 min and is technically undemanding.
Two-Suction Electrode Voltage-Clamp Recording
1991, Methods in Neurosciences
This chapter focuses on two-suction electrode voltage-clamp recording. The use of suction electrodes to implement a two-electrode voltage clamp offers advantages over conventional intracellular microelectrode-based systems. These derive from the lower resistance of suction electrodes and the greater mechanical stability of the recording configuration. In general, because the microelectrode tends to be the limiting factor in voltage clamp, the use of low-resistance suction or patch electrodes improves the quality of the recording. However, a serious drawback of suction electrodes is that the intracellular solution is quickly lost to the electrode interior. The chapter also illustrates the basic principle of two-electrode voltage clamp. One electrode is used to measure the potential across the membrane to be clamped. This membrane potential is subtracted from the desired membrane potential giving an error voltage. The error voltage is inverted, amplified, and applied to the second electrode that drives current into the cell until the error voltage is zero.
Driven shield for multi-barrel electrode
1985, Brain Research Bulletin
A driven shield for a nine-barrel micropipette containing a carbon fiber recording electrode in the center barrel is described. Two of the nine surrounding micropipettes were used as a driven shield channel to reduce capacitance between the recording electrode and the brain tissue. This method facilitates recording of single neuron activity, even in deep areas of the monkey brain, such as the amygdala and lateral hypothalamic area.
Bridge balance in intracellular recording; introduction of the phase-sensitive method
1983, Journal of Neuroscience Methods
Passing current through the microelectrode during intracellular recording produces an artifactual voltage-drop across the electrode's resistance. In modern biological amplifiers, the means of removing this artifact is through what is no more than an analog arithmetic unit which substracts a voltage, having some fixed proportion to the current being injected, from the voltage appearing at the input to the amplifier. Various techniques have evolved for determining that fixed proportion, an operation which has come to be referred to as bridge balance, and these are reviewed.
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Intracellular ca<sup>2+</sup> activity during slow synaptic hyperpolarizations in Helix pomatia
1983, Comparative Biochemistry and Physiology. Part C, Comparative
1. In the “bursting” cell RPa₁ of Helix pomatia, intracellular Ca²⁺ activity increased during the slow synaptic hyperpolarization termed LLH.
2. The Ca²⁺ increase had a double exponential time course and the kinetics provide evidence for an intracellularly located Ca²⁺ source.
3. The Ca²⁺ wave could be mimicked by dopamine and inhibited by ergometrine. dB-cAMP also enhanced the Ca²⁺ activity.
4. Intracellular K⁺ was measured during LLH.
5. An appendix by J.D.C. Lambert demonstrates that a dominant mechanism underlying LLH is the increase of K⁺ permeability.

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¹: Present address: Shell Biosciences Laboratory, Sittingbourne, Kent ME9 8AG, U.K.

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Research paperGlass microelectrode tip capacitance: Its measurement and a method for its reduction

Abstract

Neuroscience

Electroenceph. clin. Neurophysiol.

A voltage clamp study of the light response in solitary rods of the tiger salamander

J. Physiol. (Lond.)

Negative Capacity Amplifier

Wavelength dependent effects of membrane conductance in scallop photoreceptors

An analysis of extracellular potentials from single neurons in the lateral geniculate nucleus of the cat

J. gen. Physiol.

Research paper
Glass microelectrode tip capacitance: Its measurement and a method for its reduction