A transient outward current in isolated cells from the crista terminalis of rabbit heart.
- 1 November 1985
- journal article
- research article
- Published by Wiley in The Journal of Physiology
- Vol. 368 (1), 243-264
- https://doi.org/10.1113/jphysiol.1985.sp015856
Abstract
1. Voltage-clamp experiments were carried out with the objective of identifying and characterizing the time- and voltage-dependent properties of a transient outward current recorded in single myocytes from the crista terminalis region of the rabbit heart. 2. A collagenase enzymic dispersion procedure similar to that described by Desilets and Horackova (1982) was used to obtain these viable individual myocytes. Transmembrane ionic currents were recorded using a single micro-electrode voltage-clamp technique. 3. In experiments aimed at studying a tetrodotoxin-resistant transient inward current, (ICa); a transient outward current was consistently recorded following blockade of ICa with Cd2+ (5 .times. 10-4M). 4. The time and voltage dependence of the activation and inactivation of this current were measured. Its steady-state inactivation curve spans the voltage range -70 to -10mV, and it is activated between -20 and +10 mV. 5. The reversal potential of this transient outward current is approximately -75 mV in [K+]o 5 mM, suggesting that it is carried mainly by K+. 6. This transient outward current can be inhibited completely by external application of 4-aminopyridine (4-AP, 3 mM). 7. The time and voltage-dependent properties, the reversal potential, and the sensitivity to 4-AP of this transient outward current are all very similar to those of a transient outward current first identified in molluscan neurones. Hence, we have labelled it, IA. 8. Selective inhibition of IA and knowledge of its voltage- and time-dependent properties yield specific predictions concerning its role in the action potential of isolated crista terminalis cells. Consistent with these predictions, a decrease in stimulus rate is found to decrease the duration of the action potential and vice versa; and application of effective doses of 4-AP results in a substantial lengthening of the action potential. 9. These results are discussed in terms of the possible physiological role of IA in subsidiary of follower pace-maker tissue, and the anatomical and physiological heterogeneity of the sino-atrial node region of the rabbit heart.This publication has 38 references indexed in Scilit:
- Electrophysiology of single cardiac cells.The Japanese Journal of Physiology, 1984
- Effects of low-chloride solutions on action potentials of sheep cardiac Purkinje fibers.The Journal of general physiology, 1977
- On the relationship between action potential duration and tension in cat papillary muscleCardiovascular Research, 1977
- The repolarization phase of the cardiac action potential: A comparative study of rate-induced changes in its waveformJournal of Molecular and Cellular Cardiology, 1976
- A Fourier method for the analysis of exponential decay curvesBiophysical Journal, 1976
- Activities of potassium and sodium ions in rabbit heart muscle.The Journal of general physiology, 1975
- The positive dynamic current and its inactivation properties in cardiac Purkinje fibresThe Journal of Physiology, 1973
- Two Fast Transient Current Components during Voltage Clamp on Snail NeuronsThe Journal of general physiology, 1971
- Voltage clamp studies of a transient outward membrane current in gastropod neural somataThe Journal of Physiology, 1971
- The dynamic chloride component of membrane current in Purkinje fibersPflügers Archiv - European Journal of Physiology, 1967