BackgroundCyclooxygenase 2 (COX-2) elevation and subsequent prostaglandin E2 (PGE2) production play a major role in bladder inflammation and hyperactivity. EP4 receptor, a subtype of PGE2 receptors, mediates tissue inflammation and hypersensitivity. ObjectiveTo investigate the effect of intravesical botulinum toxin A (BoNT-A) on COX-2 and EP4 expression in cyclophosphamide (CYP)-induced cystitis in rats. Design, setting, and participantsExperimental (N=40) and control animals (N=20) were injected with CYP (75mg/kg intraperitoneally) or saline on days 1, 4, and 7. BoNT-A (1ml, 20unit/ml) or saline were administered into the bladder and retained for 1h on day 2. InterventionWaking cystometrograms (CMGs) were performed. Bladder and L6 and S1 spinal cord were harvested on day 8. MeasurementsCMG parameters, histology, and COX-2 and EP4 expression by immunostaining or western blotting were measured. Results and limitationsCYP induced increased bladder inflammatory reaction, bladder hyperactivity, and COX-2 and EP4 expression in the bladder and spinal cord. The CYP effects were suppressed by BoNT-A treatment. BoNT-A treatment decreased inflammatory reaction (56.5% decrease), COX-2 expression (77.8%, 61.7%, and 54.8% decrease for bladder, L6, and S1 spinal cord, respectively), EP4 expression (56.8%, 26.9%, and 84.2% decrease for bladder, L6, and S1 spinal cord, respectively), and suppressed bladder hyperactivity (intercontraction interval, 107% increase and contraction amplitude, 43% decrease). ConclusionsCYP injection activated COX2 and EP4 expression in the bladder and spinal cord and induced bladder inflammation and hyperactivity, which effects were suppressed by BoNT-A treatment. These findings suggest a potential benefit of EP4-targeted pharmacotherapy and BoNT-A treatment for bladder inflammatory conditions.