単一歩調取り細胞の活動電位と細胞内通電との関係

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タイトル別名
  • ON THE RELATIONSHIP BETWEEN DOMINANT PACEMAKER POTENTIALS AND APPLIED TRANSMEMBRANE CURRENT BY USE OF TWO BARRELS GLASSMICROELECTRODES
  • タン イッポ チョウシュリ サイボウ ノ カツドウ デンイ ト サイボウナイ

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説明

On the isolated frog's S-A node is investigated the relationship between dominant pacemaker potentials and applied transmembrane current by use of two barrels glassmicroelectrodes. namely, the dominant pacemaker potentials are recorded with one electrode, while the transmembrane current is simultaneously applied to the same cell through the other electrode. The direction of transmembrane current is alternated and the KCl solution with which is filled in the other electrode is also exchanged for many other solutions. The following results are obtained.<BR>1) Two notches which show the phase boundary of excitation appear on the plateau when the transmembrane current is applied to true or latent pacemaker cell. The one is at the site of 150-200 msec. from the upstroke of action potential, the other at the site of 400 msec.<BR>2) Applying the outward current, the notches project upward, and make the plateau increase. On the contrary, the inward current, the notches depress downward and make the plateau decrease.<BR>3) When the transmembrane current is applied through the microelectrode filled with 2M-NaCl solution instead of 3M-KCl, it is difficult to get these notches. On that occasion the prepotentials show slight changes.<BR>4) Changes above mentioned can not be. seen on the ordinary cardiac muscle fibre.<BR>5) Even if the microelectrode for transmembrane current is filled with acetylcholine or epinephrine solution instead of 3M-KCl, the rhythm during and after the transmembrane current is not changed.<BR>6) Mechanical movement in the pacemaker cell shows the similar change as the pacemaker potential timely, but variations of action potential induced by transmembrane current are independent mechanogram.<BR>The main conclusions to be drawn from these resluts are as follow.<BR>a) The dominant pacemaker rhythm is not changed even if one cell of the dominant pacemaker is stimulated.<BR>b) The phase boundary of excitation of the pacemaker cell is clearly shown by applying subthreshold transmembrane current to the exciting cell.<BR>c) It is needless to say that there is a fundamental difference between pacemaker potential and its mechanical movement in view of the fact that the variations of action potential induced by transmembrane current are independent of mechanogram.

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