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Pharmacological modulation of ureteral peristalsis in a chronically instrumented conscious pig model. I: Effect of cholinergic stimulation and inhibition.

PURPOSE
We evaluated in vivo the role of muscarinic receptors on ureteral peristaltic frequency and contraction force in a large animal model using pharmacological manipulation.


MATERIALS AND METHODS
A total of 12 female pigs weighing a mean +/- SEM of 72 +/- 4 kg were chronically instrumented using an electronic pressure monitoring catheter in the right ureter. Furthermore, nephrostomy, arterial, venous and cystostomy catheters were placed. Ureteral peristalsis was repeatedly recorded before and after the administration of atropine and carbachol.


RESULTS
Systemic and local effects of the 2 agents were observed. Compared with controls we recorded an increase in mean ureteral peristaltic frequency (2.0 +/- 0.3 versus 1.6 +/- 0.6 minutes-1, p <0.05) and mean contraction force (50.1 +/- 1.4 versus 45.3 +/- 1.7 cm H(2)O, p <0.05) during renal pelvis perfusion with 0.25 ml per minute saline. Administration of atropine or carbachol modulated neither the force of contraction nor the frequency of ureteral peristalsis in vivo (p >0.05).


CONCLUSIONS
Smooth muscle motor activity at the mid and distal ureter is not modulated by muscarinic receptors. Peristaltic frequency is directly related to the pyelocaliceal load during a rate of diuresis not exceeding animal normal diuresis plus 0.25 ml per minute. Ureteral contraction force increases only in the mid ureter with increased diuresis.