Pflügers Archiv

, Volume 364, Issue 1, pp 45–52

Membrane currents in the rabbit sinoatrial node cell as studied by the double microelectrode method

  • Akinori Noma
  • Hiroshi Irisawa

DOI: 10.1007/BF01062910

Cite this article as:
Noma, A. & Irisawa, H. Pflugers Arch. (1976) 364: 45. doi:10.1007/BF01062910


When a strand of the rabbit sinoatrial node tissue was shortened by ligation, the spatial decay of electrotonic potential decreased and the input impedance increased. In a piece of the tissue 0.2–0.3 mm in diameter apparently uniform current spread was obtained. Action potentials recorded from three different sites in this small piece occurred simultaneously and were superimposable.

In voltage clamp experiments using the double microelectrode method, the membrane potential was usually held at −30 to −40 mV, where no net current flowed. When membrane potential was suddenly changed from the holding potential, the sign and the time course of the ionic current varied with membrane potential. Hyperpolarization gave an inward current which increased with time. Depolarization gave a transient inward current followed by sustained outward current, and repolarization gave an outward current tail which exponentially subsided with a time constant of 0.37 s.

The membrane time constant was 12.0 ms. When the specific membrane capacitance was assumed to be 1 μF/cm2, the specific membrane resistance at the resting potential was 12 kΩcm2. The peak of the transient inward current on depolarization was 1.3×10−5 A/cm2.

Key words

Sinoatrial node cellVoltage clampInward currentOutward current tailCurrent voltage relation

Copyright information

© Springer-Verlag 1976

Authors and Affiliations

  • Akinori Noma
    • 1
  • Hiroshi Irisawa
    • 1
  1. 1.Department of Physiology, School of MedicineHiroshima UniversityHiroshimaJapan