著者

江原 有信 佐藤 利夫

出版者

日本動物学会

雑誌

動物学雑誌 (ISSN:00445118)

巻号頁・発行日

vol.80, no.10, pp.358-363, 1971-10

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Square pulse (17.5 V, 50 msec) was applied to oyster ventricle which had been isolated and mounted on a separation box. Myocardial activity was intracellularly recorded by means of microelectrode filled with 3 M KCl. Electric stimulation of threshold strength affected the beat interval as follows: Length of beat interval was changed by the simulation applied even during repolarization phase which corresponded to so-called refractory period. Depolarizing current did not always produce an extra action potential, and sometimes delayed the production of succeeding spontaneous action potential according to stimulating moment (Fig. 1). Hyperpolarizing current did not always elongate the interval, and often evoked an extra action potential as the result of rebound excitation th shorten the interval. Compensatory pause could not be found in these experiments. The change in length of the beat interval caused by the stimulation applied before the critical point (Fig. 2) had an opposite relation against that applied after it. The change in the beat interval caused by depolarizing current differed markedly from that produced by hyperpolarizing current. The effect of depolarizing stimulation was essentially similar to that of small potential (Ebara, 1964b) which conceivably had an important role in rhythm formation of the whole ventricle.