Effect of partial bladder outlet obstruction on detrusor compliance, excitability and contractility in rats

OBJECTIVE: Partial bladder outlet obstruction (PBOO) is believed to change the functions of the detrusor, and can lead to an overactive detrusor (OD). The aim of this study was to investigate changes in bladder compliance, excitability and contractility after PBOO in rats. MATERIAL AND METHODS: PBOO was performed for 6 weeks in 20 Wistar rats, 13 of which (OD group) had an OD and seven of which (non-OD group) did not. Simultaneously, 10 rats that underwent sham operations (control group) were also studied. Bladder compliance and cystometric capacity were identified in vivo, but bladder compliance was detected without elimination of bladder capacity. Isolated bladder smooth muscle strip (BSMS) was dissected to determine excitability and contractility. RESULTS: After 6 weeks of PBOO, cystometric capacity and compliance were significantly higher than those in the control group. Compliance was 0.170+/-0.029 and 0.149+/-0.042 ml/cmH2O in the OD and non-OD groups, respectively, compared to 0.037+/-0.017 ml/cmH2O in the control group. The corresponding cystometric capacities were 3.66+/-0.490, 3.08+/-0.590 and 1.14+/-0.225 ml. The excitability in the OD group increased significantly compared to that in the non-OD and control groups. The tension threshold for BSMS contraction was lower in the OD group, and BSMS contracted more frequently at the same tension. The contractility of the BSMS in the OD group decreased significantly compared to that in the non-OD and control groups. CONCLUSIONS: PBOO can cause a higher cystometric capacity and compliance. After PBOO, there is a chance that an OD may develop. When this occurs, the detrusor excitability increases and contractility decreases.