Post-Overdrive Suppression of the Rabbit Sinus Node Pacemaker Cells : Symposium on Sinus Node Function and Its Abnormality

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Effects of rapid stimulation (overdrive) on the isolated rabbit sinus node pacemaker cells were examined in order to elucidate the mechanism of post-overdrive suppression. Small specimens of sinus node tissue having a size of approximately half or less of the length constant of sinus nodes were driven at a fast rate through single sucrose gap methods for 10 to 120 seconds. Under the control perfusion (35℃ oxygenated Tyrode's solution), overdrive was followed by a slight suppression of spontaneous activity of the preparations. The post-overdrive suppression was accompanied by the decrease in maximum diastolic potential (MDP), overshoot (OS) and maximum rate of depolarization ((dV/dt)_<max>) as well as a slowing of the rate of diastolic depolarization. The values of MDP, OS, (dV/dt)_<max> and the spontaneous activity returned to the pre-overdrive level within a few seconds. Atropine (2 × 10^<-6>g/ml) did not influence the effects of overdrive. After ouabain administration (2 × 10^<-7>g/ml) or in the low temperature perfusate (25℃), the effects of overdrive were potentiated and a marked post-overdrive suppression characterized by a long pause of over several seconds was obtained. The decrease in MDP, OS and (dV/dt)_<max> following overdrive was also accentuated in both experimental conditions. These results would suggest that the post-overdrive suppression of sinus node is, at least partly, due to some ionic shifts following overdrive and may be potentiated by the metabolic dysfunction of pacemaker cells.
社団法人日本循環器学会の論文
1980-08-20

Post-Overdrive Suppression of the Rabbit Sinus Node Pacemaker Cells : Symposium on Sinus Node Function and Its Abnormality

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