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The pacemaker potential which is responsible for rhythm generation in heart involves four currents namely If (funny currents), currents due to T-type calcium channels,           L-type calcium channels, and Sodium calcium Exchanger (NCX) in forward mode. Of the four currents, we have studied the  contribution of NCX in rhythm generation using Ouabain in  isolated rat heart model. Isolated heart preparation of Wistar rats (n-5) perfused with Physiological salt solution (PSS) in  Langendorff mode was used for this study. The basal heart rate with Physiological salt solution (PSS) was recorded for the first 15 minutes , then Ouabain (100 microM) was added to the perfusate and the heart rate was recorded for 15 minutes, followed by 15 minute recording of heart rate again with normal Physiological salt solution (PSS). There was a significant  reduction in heart rate following perfusion with 100 microM  Ouabain (p value is 0.03 with Wilcoxon Signed Rank test). And there was partial reversal of heart rate after washout of Ouabain with normal Physiological salt solution (PSS). The significant reduction in heart rate with Ouabain, while the other three  currents remained active shows the importance of NCX in rhythm generation.


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