Summary
In order to polarize simultaneously a group of fibers of the isolated right atrium of the rabbit, a relatively large extracellular suction electrode was used and the electrotonic spread of the applied current was measured by means of microelectrodes impaled at various distances from this polarizing electrode.
This method (described in detail) seemed to be reliable since in sheep Purkinje fibers the current spread with approximately the same space and time constants as when current was injected intracellularly by means of a microelectrode (Weidmann, 1952; Fozzard, 1966). In the crista terminalis and the atrial trabecula space constants of about 1 mm and 0.65 mm respectively were found. In both preparations the membrane time constant, as measured by the time-course of electrotonic potentials, was about the same, namely 3.0 msec and 2.7 msec respectively.
From the conduction velocity and the time constant of the early exponential change of the foot of the propagated action potential, the specific membrane capacity of atrial fibers could be calculated to be about 1 μF/cm2 when assumptions were made for the specific internal resistance and the diameter of these fibers. From the values given above the specific membrane resistance of rabbit atrial fibers is of the order of 3000 ohmcm2.
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Bonke, F.I.M. Passive electrical properties of atrial fibers of the rabbit heart. Pflugers Arch. 339, 1–15 (1973). https://doi.org/10.1007/BF00586977
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DOI: https://doi.org/10.1007/BF00586977