Voiding function in mice lacking TRPV 1

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Purpose :Some investivators reported that transient receptor potential vanilloid 1 (TRPV1) played an important role during bladder inflammation, namely in hyperalgesia and hyperactivity. However, the mechanisms of activation during chronic bladder inflammation are poorly understood. Therefore, we evaluated the bladder function in mice lacking TRPV1 (TRPV1 KO) with cyclophosphamide (CYP)-induced cystitis.Methods :1.Cystometryin conscious restrained mice. TRPV1 KO and wild type control (WT) were administered CYP (150 mg/kg) or vehicle (sterile water) intraperitoneally. Forty-five hours after administration of CYP, the mice were anesthetized with sevoflurane for surgical insertion of an intravesical catheter. After the surgery, cystometry was performed in conscious restrained mice by infusing saline into the bladder at a constant rate (0.5 ml/hr).2.Histopathological examination. TRPV1 and WT were administered CYP (150 mg/kg) or vehicle intraperitoneally. Forty-eight hours after administra … More tion of CYP, the mice were anesthetized. Bladder was taken intact and fixed for 24 hours in 10% buffered formalin. Tissue (3 micrometer thickness) was stained with hematoxylin-eosin. Histological damage, including hemorrhage and inflammation were evaluated.Results :1.Cystometry in conscious restrained mice. In vehicle administrated mice, there was no significant difference in intercontraction interval (ICI) between WT and TRPV1 KO. In WT, ICI of CYP administrated group was significantly shorter than that of vehicle administrated group. In TRPV1 KO, there was no significant difference in ICI between vehicle administrated group and CYP administrated group. There was no significant difference in maximal voiding pressure between each group.2.Histopathological examination. Vehicle administrated mice had histologically normal bladders. CYP administration caused hemorrhage and inflammation of bladders in both TRPV1 KO and WT. Under microscopic examination, the area and size of inflammation in the bladder were similar in TRPV1 and WT.Conclusions :TRPV1 might be responsible for mechanisms of bladder hyperactivity in mice with CYP-induced cystitis. Less