Objective To investigate the changes of ureter function in rabbits with neuropathic urinary tract dysfunction (NUTD) and the expression of large-conductance Ca2+-activated K+ channels (BKca) in ureter smooth muscle cell.Methods Thirty Japanese White Rabbits were randomly divided into NUTD group (n =10),experimental control group (n =10) and blank control group (n =10).With a spinal cord transaction at the sixth lumbar level and the sacral cord destroyed,the NUTD group showed significant nerve damage,acontractile detrusor (ACD) without vesicoureteral reflux (VUR) in spine MRI examination and video-urodynamic assessment after two weeks.In experimental control group,only part of spinous process was bitten at the same position and spinal cord exposed without a transaction.In blank group,no operation was performed.Videourodynamic assessment,the observation of ureter function and morphology were performed 2 months after operation.The mRNA and protein expressions of BKca in ureter smooth muscle cell (USMC) were measured by real-time fluorescent quantitative PCR,immunohistochemistry and Western blot.Results Acontractile detrusor was found in all animals from NUTD group without vesicoureteral reflux.There was no significant difference in urine volume among the three groups [NUTD group:(18.5 ± 3.7)ml,experimental control group:(19.5 ± 2.4)ml,Blank control group:(17.8 ± 3.2)ml].However,the peristalsis frequency of left ureteral in NUTD group (39.0 ± 3.0) was significantly lower than that in experimental control group (44.0 ± 5.0) and blank control group (46.0 ± 4.0,P＜ 0.05).There were no abnormal changes in ureteral lamina epithelialis,lamina propria and muscular layer under light microscope among NUTD group.Compared with blank control group (BKcaα mRNA:1.02 ± 0.21,BKcaβ rnRNA:1.03 ± 0.28; BKcaα protein:0.89 ± 0.10;BKcaβ protein:1.03 ± 0.13),the mRNA expressions of BKcaα (2.89 ± 0.67) and BKcaβ(4.59 ± 1.22) were respectively upregulated for 2.89 and 4.59 times in NUTD group (P＜0.001),and expressions of BKcaα (1.35 ± 0.32) and BKcaβ (1.47 ± 0.10) protein also significantly increased (P＜0.001).Conclusions The ureter dysfunction occurs prior to vesicoureteral reflux and the pathological changes in ureter of the rabbits with NUTD.The increased expression of BKca inhibits the ureteral excitability and contractility,which may play an important role in upper urinary tract dysfunction of the rabbits with NUTD.