Action potential of isolated human ureter recorded with sucrose gap technique.

The action potential of human ureter was recorded in vitro by sucrose gap technique and the effects of some cations and drugs were studied. The action potential was composed of an initial fast component of spike and a subsequent slow component, a plateau, without a definite after-positive potential. Duration of the action potential was 1.0 +/- 0.1 (mean +/- standard deviation, n = 5) seconds at resting membrane potential level and 0.8 +/- 0.1 seconds at 90 per cent of the repolarization level. Ratio of plateau potential to spike potential was 80 +/- 4 per cent. The results of ionic influence suggested that calcium played an important role in the generation of spike potential and sodium in the generation of plateau potential. The application of noradrenaline and serotonin showed an excitatory effect which was observed as an increase of spontaneous discharge with depolarization of membrane potential and slow depolarization preceding the action potential. The slow depolarization was never observed in control preparations. These findings suggested that the ureter might have the capacity to generate a pacemaker-like slow depolarization which could conceivably relate to the automaticity of the ureter. Acetylcholine showed an excitatory effect only when the preparation was pretreated by physostigmine.