Mechanisms of pelvic organ cross-talk : 1 : peripheral modulation of bladder inhibition by colorectal distension in rats
Faculty of Medicine and Health Sciences
The journal of urology. - Baltimore, Md
, p. 765-771
University of Antwerp
Purpose Bladder activity can be inhibited by afferent input from the colorectum (inhibitory rectovesical reflex, IRVR). We evaluated the functional response of the rat urinary bladder to non-noxious and noxious colorectal distension (CRD), and investigated peripheral modulation (mechanical and pharmacological) of this response. Materials and Methods Sprague-Dawley rats (N=70, females) were used for this study. We evaluated the effect of non-noxious (20 mmHg) and noxious (40, 60mmHg) CRD on the volume threshold for micturition (VT) and on bladder activity in a filled bladder. Secondly, we studied the effect of rectal balloon size (1.5cm versus 3.5cm long), and of rectal administration of 2% lidocaine jelly and of a 1mM allyl isothiocyanate solution, on the IRVR. Results Sixty mmHg CRD increased the VT (0.640±0.056ml; control: 0.448±0.035ml; p<0.001). Bladder contraction frequency (BCF) was significantly decreased by both 40 (0.62±0.06/min; p<0.001) and 60mmHg CRD (0.33±0.05/min; p<0.001) compared to control measurements (0.77±0.03/min). These effects were reversible and pressure-dependent (p<0.001) and more pronounced (p=0.004) with a large rectal balloon (40mmHg CRD: 0.35±0.12/min, 60 mmHg CRD: 0.07±0.04/min). Significant graded inhibition of amplitude and duration of bladder contractions was not shown. The IRVR was reversibly abolished by intrarectal administration of lidocaine. Intrarectal administration of allyl isothiocyanate significantly increased the effect of noxious CRD on BCF. Conclusions Only noxious levels of CRD initiate the IRVR. The effect increases with rectal balloon size and with intrarectal administration of allyl isothiocyanate, and is reversibly abolished by lidocaine. Our results suggest that spinal interneurons are the mechanism behind the IRVR.