Abstract: BACKGROUND: Spinal cord injury often leads to neurogenic bladder with hyperreflexia of the forced urethral muscle, but there is a lack of clear understanding of its pathogenesis and treatment, and establishing a stable and reliable animal model has an important impact on revealing its pathomechanisms and exploring therapeutic approaches.
OBJECTIVE: To investigate the effect of the number of times to urinate on neurogenic model rats after complete spinal cord transection in order to improve the postoperative survival and modeling rate of neurogenic model rats.
METHODS: Out of 46 female Sprague-Dawley rats, 6 were selected as the sham-operated group using the random number table method, and the remaining 40 rats were randomly divided into 0, 1, 3, and 5 times daily urination groups after complete spinal cord transection modeling, with 10 rats in each group. The residual urine volume was measured every 3 days within 19 postoperative days, and the survival and modeling were observed on the 19th day after the operation, and urodynamics tests and contraction experiments of isolated forced urethra muscle strips were performed.
RESULTS AND CONCLUSION: (1) Survival and modeling rate: there was 10% survival rate and 10% modeling rate in the group of 0 times daily urination; 20% survival rate and 10% modeling rate in the group of 1 time daily urination; 70% survival rate and 70% modeling rate in the groups of 3 and 5 times daily urination. (2) Residual urine volume: compared with the sham-operated group, the residual urine volume of the groups of 3 and 5 times daily urination was significant increased on postoperative days 3, 6, 9, 12, and 15 (P < 0.01); the residual urine volume of the groups of 3 and 5 times daily urination was increased on the 18th day after surgery (P < 0.05). Compared with the 3 times daily urination group, the residual urine volume was decreased in the 5 times daily urination group on the 6th day after surgery (P < 0.05), while there was no significant difference in the residual urine volume between the 3 and 5 times daily urination groups on the 3rd, 9th, 12th, 15th, and 18th days after surgery. (3) Urodynamics: Compared with the sham-operated group, the differential pressure at the point of leakage was significantly reduced (P < 0.01) and the maximal volume was significantly increased (P < 0.01) in the 3 and 5 times daily urination groups. There was no statistical difference in the differential pressure at the point of leakage and the maximal volume between the 3 and 5 times daily urination groups. (4) Muscle-strip contraction test of isolated detrusor muscles: Compared with the sham-operated group, the contraction amplitude and frequency of detrusor muscle strips were significantly reduced in the 3 and 5 times daily urination groups (P < 0.01). There was no statistically significant difference in the contraction amplitude and frequency of detrusor muscle strips between the 3 and 5 times daily-urination groups. In conclusion, assisted urination is one of the keys to establish a successful neurogenic model of urethral reflexes, and there is no significant difference in the effects of urinating 3 or 5 times a day on the neurogenic model. It is recommended to urinate at least 3 times a day based on the actual workload and the modeling rate. 

中国组织工程研究杂志出版内容重点：组织构建；骨细胞；软骨细胞；细胞培养；成纤维细胞；血管内皮细胞；骨质疏松；组织工程

Key words: neurogenic bladder model, hyperreflexia of the urethral muscle, spinal cord injury, complete spinal cord transection, number of urinations, manually assisted voiding techniques, SD rat, engineered animal model