Propagation characteristics of the electrical impulse in the normal and obstructed ureter as determined at high electrophysiological resolution

OBJECTIVE To investigate the propagation of the electrical impulses in a unilateral ureteric obstruction model using a high-resolution technique in vivo. MATERIALS AND METHODS In Wistar rats (n = 15), the left mid-ureter was occluded and the electrical activity was recorded from the proximal and distal part of the obstructed ureter and from the right ureter at different times up to 2 weeks post-obstruction using 64 extracellular electrodes. RESULTS In the left ureter, impulses propagated in an antegrade direction at a frequency of 15.5 +/- 1.3/min and a velocity of 1.6 +/- 0.1 cm/s. Immediately post-obstruction, the proximal part showed an increase in frequency (19.1 +/- 2.5/min; P < 0.05) followed by a gradual decrease (at 2 weeks: 2.5 +/- 1.2/min; P < 0.001). The velocity of these impulses decreased gradually (at 2 weeks: 0.5 +/- 0.1 cm/s; P < 0.05). Distally, the antegrade propagations gradually disappeared and, at 1 week, 33% of ureters showed retrograde impulses and 67% displayed no electrical activity. The frequency of both antegrade and retrograde impulses distal to the obstruction dropped immediately after obstruction so that, at 1 day, it was 1.0 +/- 0.3 and 1.5 +/- 0.2/min, respectively (P < 0.01 for both). The velocity of these antegrade and retrograde impulses showed a significant rise throughout the post-obstruction period. The right ureter showed only a transient increase in frequency from 18.7 +/- 2.7 to 30.3 +/- 6.1/min (P < 0.05). CONCLUSIONS Using this high-resolution technique, it is concluded that, after ureteric obstruction, there were immediate and significant changes in the propagation of electrical impulses in the proximal and distal left ureter and in the right ureter, all of which behaved differently. This data may provide a better insight into the electrophysiological function of the normal and obstructed ureter.