BERKELEY, CA (UroToday.com) - Irritable bowel syndrome and interstitial cystitis frequently overlap.

Ustinova and colleagues from the University of Pittsburg have shown that acute colitis sensitizes urinary bladder afferents to both mechanical and chemical stimuli and that chronic colitis likewise produces neurogenic cystitis. Convergence of afferent pathways from the bladder and bowel is known to be a common feature of visceral interneurons which are thought to mediate vesico- and colono-sphincteric reflexes and colono-vesical corss-inhibitory interactions. Studies performed at the University of Pittsburg employing single unit C-fiber bladder afferent recording revealed that acute colonic irritation is capable of sensitizing urinary bladder afferents to mechanical and chemical stimuli, and interruption of the neural input to the bladder can ameliorate this effect, suggesting a direct afferent pathway from the colon.

The investigators hypothesized that chronic irritation of the colon releases neuropeptides from bladder afferent endings leading to receptor sensitization and neurogenic inflammation. They recorded single unit C-fiber bladder activity from fine filaments of the pelvic nerve in urethane-anesthetized Sprague-Dawley female rats and assessed their responsiveness to mechanical (bladder distention) and chemical (intravesical capsaicin, bradykinin, or substance P) stimulation 10 days following intracolonic administration of trinitrobenzenesulfonic acid (TNBS) or vehicle. To evaluate the role of C-fiber afferents and their associated neuropeptides, animals were pre-treated with capsaicin or vehicle 3 days prior to TNBS administration.

Chronic colonic irritation in the rat with TNBS sensitizes urinary bladder afferents to mechanical and chemical stimuli and induces bladder mastocytosis. A role of C-fiber afferents was further substantiated in this model of neurogenic cystitis as capsaicin pretreatment significantly ameliorated these effects. The authors experiments provide further support for neural processes in mediating cross-sensitization of pelvic organs and the overlap of PBS/IC, irritable bowel syndrome, and other chronic pelvic pain disorders.

Elena E Ustinova, Dmitriy W Gutkin, and Michael A Pezzone

American Journal of Physiology Renal Physiology (August 22, 2006)
doi:10.1152/ajprenal.00162.2006.

Written by Philip M. Hanno, MD, a Contributing Editor with UroToday.

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