Pacemaker activity of the pelvicalyceal border recorded by an intracellular glass microelectrode

Applying intracellular glass microelectrodes to the smooth muscle obtained from the guinea pig pelvicalyceal border, we have succeeded in recording periodic spontaneous action potentials, the so-called slow waves, which are characteristic of a pacemaker. This experiment proved that the pacemaker exists at the pelvicalyceal border. The slow waves originate from the pelvicalyceal border, close to the papilla renalis; they show a biphasic pattern and have the characteristics of a spontaneously excitable cell. The resting potential is 42.3 +/- 1.1 mV, the spontaneous depolarizing potential is 12.1 +/- 0.7 mV, and the depolarizing period is 12/min. The rate of rise of the potential is 22.9 +/- 2.1 mV/s in the first slow depolarization phase, and 50.9 +/- 9.5 mV/s in the following rapid depolarization phase. The rate of decline of the potential is 47.3 +/- 5.4 mV/s in the repolarization phase.