Spatial and temporal variations in pacemaking and conduction in the isolated renal pelvis

Abstract

In renal pelvis preparations isolated from the sheep, the location of the pacemaker and the pathway of conduction of the electrical impulse in the pelvis were analyzed in detail. An electrophysiological acquisition system was used allowing simultaneous recordings from 240 extracellular electrodes. Reconstruction of the spread of activity showed that the site of the pelvis pacemaker was, in virtually all cases, located at the pelvicalyceal border and never in the body of the pelvis or in the area of the pelviureteric junction. One single pacemaker was responsible for a particular spread of activation, and fusion of activity originating from two or more pacemakers did not place. Furthermore, spontaneous shifts of the pacemaker could occur from one site to another along the pelvicalyceal border. Conduction from the site of the current pacemaker to the pelviureteric junction and the ureter was slow, inhomogeneous, and contorted. Multiple instances of partial or total conduction block were seen at all levels in the pelvis and were not restricted to the pelviureteric junction. The occurrence of the conduction block did not seem to be related to the length of the preceding interval, implying that the refractory period did not play a major role in the genesis of intrapelvic conduction block. In conclusion, high-resolution mapping of the renal pelvis is possible and reveals location and behavior of the pacemaker and documents inhomogeneities in conduction and conduction block.

Macroscopic electrical propagation in the guinea pig urinary bladder

“…The 64 recording electrodes were connected through shielded wires to 64 AC preamplifiers, where the signals were amplified (4,000 times), filtered (2-400 Hz), and digitized (1-kHz sampling rate) before being stored as previously described (32) (Fig. 1C).…”

“…2A). The local activation time of a wave was identified by the moment of maximum negative slope and marked with a cursor (21,32), whereby the reference time was determined by the timing of the first detected wave (t ϭ 0.0 s at electrode 3 in column c in Fig. 2B).…”

“…Other technologies, such as optical mapping, have recently been introduced to study the propagation of action potentials and calcium waves in the whole bladder (30). Another mapping technology, multielectrode mapping with a large number of extracellular electrodes, has been used to analyze the propagation of electrical impulses in other smooth muscle organs, such as the stomach (33), the myometrium (34), the renal pelvis (32), and the ureters (21,22) under normal and pathological conditions. In the current study, using the same technology, we have recorded the electrical activities from several parts of the guinea pig bladder at different bladder volumes and analyzed their patterns of propagation.…”

Pacemaker activity in the upper urinary tract

“…It has been postulated that multiple pacemakers may fire simultaneously as coupled oscillators and that their summation gives rise to the ureteral action potential and peristaltic activity (Golenhoffen and Hannappel, 1973;Constantinou and Yamaguchi, 1981). In contrast in the sheep kidney, pacemakers appear to fire individually and with time, pacemaker activity shifts from one site to another along the pelvi-calyceal border (Lammers et al, 1996). In the sheep kidney at any one time, it appears that one single pacemaker is responsible for a particular spread of activation, and fusion of activity originating from two or more pacemakers does not take place.…”

Pacemakers in the upper urinary tract

“…Furthermore simultaneous extracellular recordings from numerous sites on the sheep renal pelvis have revealed that only one pacemaker region on the pelvi-calyceal border is active at any one time and that the pathway of conduction might meander throughout the renal pelvis. The site of the pacemaker signal on the pelvi-calyceal border can shift spontaneously, conduction delays or block of the wave of excitation can occur at any point or time (Lammers WJ et al 1996). These observations do not support the concept of summation of subthreshold pacemaker activity.…”