Role of INa and Ito in rate-dependent effect of ajmaline: action potential voltage clamp analysis
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| Year of publication | 2004 |
| Type | Conference abstract |
| MU Faculty or unit | |
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| Description | The efficacy of antiarrhythmic drugs is significantly affected by their frequency dependent effect. This study was aimed to assess how Ca2+-independent currents contribute to the ajmaline-induced rate-dependent changes of action potential (AP) waveform in rat ventricular myocytes. To bring the analysis nearer to natural conditions, we used the AP voltage clamp method. In control, the gradual prolongation of AP correlated with gradual decrease of charge carried by transient outward current Ito measured in the AP voltage clamp mode. Under the effect of ajmaline, marked gradual decrease of AP amplitude correlated with gradual decrease of charge carried by sodium current INa. We conclude that INa, slowly recovering form ajmaline-induced block, can account for the gradual decrease of AP amplitude whereas the suppressed Ito was unable to induce significant changes of AP. |
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