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Purpose:

Autonomous bladder activity can take the form of localized micromotions (MMs), suggesting that the detrusor may be arranged into component modules, of which each is capable of contracting autonomously. We examined MMs in isolated whole rat bladder and the effects of partial bladder outlet obstruction as a model of detrusor overactivity (DO) to ascertain whether altered modular activity could be an etiological factor in DO.

Materials and Methods:

A total of 12 adult female Sprague-Dawley rats underwent obstruction or sham operation for 1 or 4 weeks. Bladders were microsurgically removed and mounted in whole organ tissue baths. Recordings of intravesical pressure and simultaneous registration of intramural contractions were performed under standardized conditions.

Results:

Prior to filling MMs took the form of localized contractions near the vesicoureteral junction in sham operated animals and multifocal microcontractions in obstructed animals. Intravesical volume increases were associated with a change in localized MMs to propagated contraction waves. In sham operated animals stretch resulted in increased MM frequency but decreased amplitude. After obstruction stretch elicited highly coordinated MMs and enhanced intravesical pressure transmission. The time since surgery did not alter observations in the sham or obstructed group.

Conclusions:

Detrusor muscle in isolated bladders under conditions modeling urine storage may have a functional modular arrangement with the basolateral region most active prior to filling. Peripheral factors determining intravesical pressure include the number of modules active, coordination and intramural tension at other sites. After bladder outlet obstruction more modules are active at baseline and their coordination is enhanced by stretch, leading to increased pressure fluctuations. Such changes may contribute to the development of DO.

References

  • 1 : New concepts in relation to urge and detrusor activity. Neurourol Urodyn1993; 12: 463. Google Scholar
  • 2 : Micturition and premicturition contractions in unanesthetized rats with bladder outlet obstruction. J Urol1994; 151: 244. LinkGoogle Scholar
  • 3 : Motility of the urinary bladder in cats during filling at physiological rates. II. Effects of extrinsic bladder denervation on intramural tension and on intravesical pressure patterns. Acta Physiol Scand1977; 101: 176. Google Scholar
  • 4 : Urine storage mechanisms. Prog Neurobiol1995; 46: 215. Google Scholar
  • 5 : Model of peripheral autonomous modules and a myovesical plexus in normal and overactive bladder function. Lancet2001; 358: 401. Google Scholar
  • 6 : Micromotions of bladder wall in chronic pelvic pain (CPP): a pilot study. Int Urogynecol J Pelvic Floor Dysfunct2001; 12: 89. Google Scholar
  • 7 : Autonomous activity in the isolated guinea pig bladder. Exp Physiol2003; 88: 19. Google Scholar
  • 8 : Effects of intravesical administration of the K+ channel opener, ZD6169, in conscious rats with and without bladder outflow obstruction. J Urol1999; 162: 943. LinkGoogle Scholar
  • 9 : Influence of temperature on activity of the isolated whole bladder preparation of neonatal and adult rats. Am J Physiol Regul Integr Comp Physiol2000; 278: R238. Google Scholar
  • 10 : Multiple-coupled pacemaker system in renal pelvis of the unicalyceal kidney. Am J Physiol1981; 241: R412. Google Scholar
  • 11 : A myogenic basis for the overactive bladder. Urology1997; 50: 57. Google Scholar
  • 12 : Connexins 43 and 26 are differentially increased after rat bladder outlet obstruction. Exp Cell Res2002; 274: 216. Google Scholar
  • 13 : Physiology of the urinary bladder and urethra. Ann Intern Med1980; 92: 312. Google Scholar
  • 14 : Innervation of bladder and bowel. Ciba Found Symp1990; 151: 2. Google Scholar
  • 15 : Decrease and disappearance of intramural neurons in the rat bladder during post-natal development. Neurosci Lett1996; 218: 103. Google Scholar
  • 16 : Identification of the cells underlying pacemaker activity in the guinea-pig upper urinary tract. J Physiol1999; 519: 867. Google Scholar
  • 17 : kit positive cells in the guinea pig bladder. J Urol2002; 168: 832. LinkGoogle Scholar
  • 18 : Gap junctions and connexin expression in human suburothelial interstitial cells. BJU Int2002; 90: 118. Google Scholar
  • 19 : A neurologic basis for the overactive bladder. Urology1997; 50: 36. Google Scholar

From the Urophysiology Research Group (MJD, IJH, JIG), School of Surgical Sciences, University of Newcastle, United Kingdom, and Department of Clinical Pharmacology (PH, RKP, K-EA), Lund University Hospital, Sweden

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