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Effect of Calcium on the Membrane Potentials of Single Pacemaker Fibres and Atrial Fibres in Isolated Rabbit Atria


IN previous investigations it was found that in the isolated dog heart1, as well as in isolated guinea pig atria2, calcium produced a marked change in the sino-atrial rhythm. The curve relating changes in sino-atrial rhythm to external calcium concentration showed a typical pattern: an ascending limb, which reached a maximum at several times the normal calcium concentration, and a descending limb, indicating a rate-decreasing component of the action of calcium at high concentrations. A similar curve was obtained from experiments with isolated rabbit atria, as shown in Fig. 1 (for method, see ref. 2).

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  1. Seifen, E., Flacke, W., and Alper, M. H., Amer. J. Physiol. (in the press).

  2. Schaer, H., J. Pharmacol. (in the press).

  3. Trautwein, W., Pharmacol. Rev., 15, 277 (1963).

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  4. Marshall, J. M., Circ. Res., 5, 664 (1957).

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  5. Hoffman, B. F., and Cranefield, P. F., Electrophysiology of the Heart, (McGraw-Hill Book Co., Inc., New York, 1960).

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SEIFEN, E., SCHAER, H. & MARSHALL, J. Effect of Calcium on the Membrane Potentials of Single Pacemaker Fibres and Atrial Fibres in Isolated Rabbit Atria. Nature 202, 1223–1224 (1964).

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