Simultaneous registration of intraabdominal and intravesical pressures during cystometry in conscious rats-effects of bladder outlet obstruction and intravesical PGE2

Aims: A method was developed and evaluated to simultaneously register intraabdominal pressure (IAP) and intravesical pressure (IVP) during cystometry in conscious rats. In addition, IAP and IVP were recorded in rats with experimental detrusor overactivity (DO). Methods: Sprague Dawley rats (n = 24) were used. Six female rats were subjected to partial bladder outlet obstruction for 2 weeks. A catheter was implanted into the bladder to record the IVP, and a balloon-fitted catheter was positioned in the abdominal cavity to record the IAP. PGE(2) was given intravesically to induce DO. Detrusor pressure (DP) was defined as the IVP corrected for IAP. Results: Recorded as increases in LAY, all rats of both sexes exhibited abdominal straining during every void. In controls, a maximal LAP of 6.0 +/- 1.4 cmH(2)O (range 3-15 cmH(2)O) was registered (n = 12) at the time of the flow pressure (FP). Intravesical administration of PGE2 or BOO did not affect the IAP at basal pressure, FP or micturition pressure. Changes in LAP due to movement or non-voiding-related straining were subtracted from IVP to generate DP and to visualize DO after BOO or intravesical PGE(2). Conclusions: The conscious rat uses abdominal straining during voiding, and maximal LAP is recorded at the onset of urinary flow. Simultaneous registration of IAP and IVP during the micturition cycle in conscious rats is a convenient method for accurate quantification of pressures inside the bladder and for studying "true" DO without interference from movement artifacts.