An Assessment of the Double Sucrose-Gap Voltage Clamp Technique as Applied to Frog Atrial Muscle

Abstract

The homogeneity of voltage clamp control in small bundles of frog atrial tissue under double sucrose-gap voltage clamp conditions was assessed by intracellular microelectrode potential measurements from cells in the test node region. The microelectrode potential measurements demonstrated that (1) good voltage control of the impaled cell existed in the absence of the excitatory inward currents (e.g., during small depolarizing clamp pulses of 10-15 mV), (2) voltage control of the impaled cell was lost during either the fast or slow excitatory inward currents, and (3) voltage control of the impaled cell was regained following the inward excitatory currents. Under nonvoltage clamp conditions the transgap recorded action potential had a magnitude and waveform similar to the intracellular microelectrode recorded action potentials from cells in the test node. Transgap impedance measured with a sine-wave voltage of 1,000 Hz was about 63% of that measured either by a sine-wave voltage of 10 Hz or by an action potential method used to determine the longitudinal resistance through the sucrose-gap region. The action potential data in conjunction with the impedance data indicate that the extracellular resistance (R(s)) through the sucrose gap is very large with respect to the longitudinal intracellular resistance (R(i)); the frequency dependence of the transgap impedance suggests that at least part of the intracellular resistance is paralleled by a capacitance. The severe loss of spatial voltage control during the excitatory inward current raises serious doubts concerning the use of the double sucrose-gap technique to voltage clamp frog atrial muscle.

Calcium‐sodium antagonism on the frog's heart: a voltage‐clamp study.

“…619 620 C. BENNINGER AND OTHERS Possible limitations of membrane current measurement due to an imperfect voltage control at high membrane conductances were considered elsewhere (Haas, Kern, Benninger & Einwachter, 1975). Recently a detailed methodological study of the double sucrose gap technique as applied to frog atrial bundles has been presented by Tarr & Trank (1974 (Niedergerke, 1963;Chapman & Tunstall, 1971 (Morad & Orkand, 1971;Morad & Goldman, 1973), frog atrial tissue exhibits a phasic (transient) tension in response to shortlasting depolarizing clamps (Einwachter et al 1972;Vassort & Rougier, 1972). During long-lasting depolarizations the phasic tension is followed by, and partially superimposed on, the development of a tonic contraction.…”

Three‐micro‐electrode voltage clamp experiments in calf cardiac Purkinje fibres: is slow inward current adequately measured?

“…There is general agreement that, in principle, voltage clamp experiments in heart can provide valuable information on events underlying excitation and contraction (see for example Reuter, 1974;Fozzard & Beeler, 1975). Much controversy remains, however, concerning the validity of experimental methods presently in use (Johnson & Lieberman, 1971;Tarr & Trank, 1974;Connor, Barr & Jakobsson, 1975;Attwell & Cohen, 1977). Since cardiac preparations cannot be space-clamped with an internal longitudinal electrode, some spatial and temporal non-uniformity must exist.…”

The Effect of Quinidine on Membrane Electrical Activity in Frog Auricular Fibres Studied by Current and Voltage Clamp

“…Owing to the fact that a certain loss of voltage control exists when voltage clamping the preparation (Johnson & Lieberman, 1971;Tarr & Trank, 1974;[eoty & Poindessault, 1974;Ramon, Anderson, Joyner & Moore, 1975), the results obtained from the experiments described here must be considered as In this work, the phenomenological equations proposed by Hodgkin & Huxley (1952c) will be used to describe the effects of quinidine on the transmembrane conductances and their parameters.…”