BACKGROUNDOveractive bladder (OAB) can be caused by many factors such as inflammation, bladder outlet obstruction, neurogenic factors. We performed an intraperitoneal (ip) injection of cyclophosphamide to induce cystitis in rats, which causes their detrusors to overact, to provide a valuable disease model for discussing OAB pathogenesis and to study effective curing methods.

METHODSFemale Sprague-Dawley rats were induced to form cystitis by cyclophosphamide (200 mg/kg, ip). The day after the injection, two catheters were inserted into each rat's bladder to study its urodynamics. The BL-410 model bio-function experimental system was used to monitor bladder pressure while the rats were conscious. Unstable detrusor contractions appear in the urine storage period as a standard to determine OAB, and the positive rate was calculated. Urodynamic parameters such as bladder basal pressure (BP), maximum voiding pressure (MVP), intercontraction interval (ICI), spontaneous activity (SA), maximum cystometric capacity (MCC), and bladder compliance (BC) were recorded in each group, and a light microscope was used to observe the pathological changes in the rat bladder tissue.

RESULTSThe detrusor instability rate of the model group was 83.33%. The MVP, MCC and BC of rats in the model group were lower than the control group (P < 0.01), and the BP, ICI and SA of the model group rats were higher than the control group (P < 0.01). The difference between the control group and the model group is statistically significant. The model group rats' bladder walls swelled and bled, the submucosa thickened and leukocyte infiltration became serious.

CONCLUSIONSAcute cystitis and OAB symptoms can be induced by ip injections of cyclophosphamide in rats. This can provide a valuable animal model to study OAB in human beings.