ABSTRACT Objective: To establish the detrusor overactivity (DO) model induced by visceral hypersensitivity (VH) and investigate the relationship between mast cell (MC) infiltration and DO. Materials and Methods: Sixty rats are divided into 4 groups randomly: Group 1:Baseline group; Group 2: DO group; Group 3: CON group; Group 4: VH group. The colorectal distension (CRD) and abdominal withdral reflex (AWR) scores are performed to evaluate VH. The cystometric investigation and histological test of MC infiltration are assessed. Results: The threshold pressure of CRD in the VH group is significantly lower than that in the CON group (P<0.001). At the distension pressure ≥20 mmHg, the AWR scores of the VH group are significantly higher than those of the CON group (10 mmHg: P=0.33; 20 mmHg: P=0.028; 40 mmHg: P<0.001; 60 mmHg: P<0.001; 80 mmHg: P<0.001). DO model is successfully established in the VH group (DO rate=100%). Compared with the CON group, the numbers of MC infiltration are significantly increased in the VH group, including submucosa of bladder (P<0.001), mucosa lamina propria/mesentery of small intestine (P<0.001), and mucosa lamina propria/mesentery of large intestine (P<0.001). Furthermore, more MC activation as well as degranulation are observed in the VH group. Conclusions: It is indicated that DO model can be established in the VH rats. The MC infiltration may play an important role in DO induced by VH, and may be helpful to understand the mechanisms of DO in VH patients.

Objective To improve the model for establishment and evaluation of detrusor overactivity in female Wistar rats. Materials and Methods We ligated the perineal urethra of female Wistar rats and then performed filling cystometry. The probability of detrusor overactivity, bladder capacity, peak voiding pressure and histological changes were investigated. Results Detrusor overactivity ratio of the obstruction group was 32.4%. Bladder capacity increased from 0.273 ± 0.036mL in control group to 0.89 ± 0.19mL in detrusor overactivity group (P < 0.001), and peak voiding pressure increased from 45.9 ± 4.1 cm.H2O to 63.5 ± 17.4cm.H2O (P = 0.007). For obstruction group, compared to no detrusor overactivity rats, detrusor overactivity rats had higher bladder capacity (0.89 ± 0.19mL versus 0.43 ± 0.09mL, P < 0.001) and higher peak voiding pressure (63.5 ± 17.4cm.H2O versus 44.8 ± 6.2cm.H2O, P = 0.005). Detrusor overactivity rats were classified according to peak voiding pressure (49.2 ± 4.2cm.H2O versus 80.8 ± 7.1cm.H2O, P < 0.001). Moreover, bladder weight increased significantly in detrusor overactivity rats (P = 0.003, P = 0.028) and detrusor histological hypertrophy was observed. Conclusions Ligating perineal urethra and filling cystometry with intra-urethral cannula approach is a simple and easily reproducible method to establish and evaluate the model of detrusor overactivity in rats.