Contractile behaviour of the human pyelo-ureteral musculature. II. Repetitive electrical stimulation effects

In normal proximal and distal pyeloureteral human strips and in pathological reflux or obstructive segments the influence of repetitive electrical stimulation at frequencies between 0.01 and 200 Hz on their contractile behaviour was studied. Between 0.01 and 1 Hz baseline tone and maximum amplitude of contraction were dependent on stimulation frequencies, but some strips showed an irregular response pattern. At frequencies between 1 and 200 Hz half of the strips showed a typical "on" and "off" contraction (at the beginning and end of the stimulus period respectively) separated by a plateau. We consider the "off" reaction to be a response to an ionic displacement at the end of the stimulus. Spontaneous activity was mostly observed in Tyrode solution and in calix and pyelum. Transmural nerve stimulation did not change the contraction patterns.