and sudden fast discharge during recovery from high [K+]
to Tyrode solution. Vos, ThVos and sudden fast discharge during recovery from high [K+]o to Tyrode solution. The SAN was quiescent in 19.2 mM [K+]o and recovery in the Tyrode solution started at the downward arrow and continued for the rest of the figure. In panel A, subthreshold stimuli (15 V, 3 ms; leftward oblique arrows) were applied at 6 min-1. Subthreshold ThVos is shown at higher gain in inset 1. In panel B, the star indicates ThVos leading to spontaneous discharge and the rightward oblique arrow points to the depolarising slope of a ThVos that initiated an AP and fast rhythm. In the inset 2, the arrow points to the peak of Vos. The trace indicated by a horizontal line ending with two dots is shown at higher gain in inst 3, where the dots and the shaded areas emphasize the growth of Vos. In the inset 4, the subthreshold stimuli initiated ThVos at the resting potential (upward arrow), but not during early DD1 (leftward oblique arrow). The dots show ThVos that began prior to the electrical stimulus.