Cystometric evaluation of partial urinary bladder outlet obstruction model in conscious rats

Abstract

Urinary frequency and urgency in benign prostatic hyperplasia (BPH) are associated with involuntary detrusor contractions. Animals with partial bladder outlet obstruction (BOO) exhibit detrusor instability showing non-micturition contractions (NMC) on cystometrogram (CMG). We investigated the conscious CMG and natural voidings (NV) of rats with BOO. The effect of 5-HT1A antagonist WAY100635 (WAY) on NMC was also evaluated in the BOO rats. The proximal urethra was loosely ligated. NV and CMG were measured 2–6 weeks post BOO. The ligature was removed and the bladder was cannulated 2 days prior to CMG. The bladder weight of BOO was increased significantly 3–6 weeks post BOO. [Bladder weight (g): BOO 0.53±0.04 (n=18), sham 0.18±0.01 (n=16)]. Histopathological abnormalities were seen in the bladders and kidneys in BOO rats. No NV difference was observed between BOO and sham. The void pressure (VP), void interval (VI) and void volume (VV) were not significantly different within 3–6 week BOO rats, however the VI and VV were increased and significantly different from sham rats. [VI (min): BOO 13.8±0.8, sham 6.16±0.4 (p<0.01); VV (ml): BOO 2.7±0.3, sham 1.3±0.1 (p<0.01)]. NMC was exhibited in 9 of 17 BOO rats, but not in sham controls. WAY (0.1 mg/kg, iv) significantly inhibited NMC. [Inhibition time (min): WAY 7.4±3.1, veh 0±0 (n=4, p<0.05); Amplitude inhibition (mmHg): WAY −11.3±2.9, veh −0.5±1.2; (n=4, p<0.05)]. These results indicate that BOO could induce increased bladder capacity and void interval and NMC in conscious rats. WAY100635 produced inhibitory effect on NMC, suggesting that 5-HT1A antagonist may inhibit detrusor instability associated with outlet obstruction in BPH.