Effect of temperature on pacemaker activity of rabbit sinus node

Abstract

The effect of temperature on the membrane potential of the true pacemaker of the rabbit sinus node was investigated and compared with that of latent pacemakers and atrial fibers. The amplitude of the true pacemaker action potential was constant between 34 and 42[degree] C, and it declined above 42[degree] C. On the other hand, the slow diastolic depolarization and maximal rate of rise of the action potential increased consistently until 43[degree] C. For latent pacemakers and atrial fibers, the action potential diminished above 40 and 36[degree] C, respectively. In the action potential of the true pacemaker, the slopes of the different phases had the following Q10 values: upstroke 2.7, plateau 4.7, final repolarization 2.6, and slow diastolic depolarization 3.2. The durations of the slow diastolic depolarization and of the action potential were changed equally at all temperature levels examined. Conduction velocity in the sinus nodal area increased with an increase in temperature, even if that in the atrium stopped. Moreover, it was more sensitive to temperature change than that in the atrium.