Differential expression of bladder neurotrophic factor mRNA in male and female rats after bladder outflow obstruction

PURPOSE: We validated a male rat model of bladder outflow obstruction and compared the expression of bladder neurotrophic factor mRNA in male and female rats 6 weeks after bladder outlet obstruction. MATERIALS AND METHODS: We examined the proximal urethra in male Wistar rats. Urethral lumen reducing ligatures were placed in 15 females and 19 males, while 10 male and 10 female controls underwent sham surgery. Awake cystometry was performed 6 weeks after surgery. Ribonuclease protection assay was used to measure changes in bladder neurotrophic factor mRNA expression in the 2 sexes. RESULTS: Average bladder capacity in rats with bladder outlet obstruction increased 3-fold in males and 4.4-fold in females compared with controls, while bladder weight increased 2.2 and 4.3-fold, respectively. Filling and threshold pressure increased significantly and nonvoiding bladder contractions were recorded in 100% of female and 80% of male rats with bladder outlet obstruction. An 8-fold increase in bladder brain derived neurotrophic factor mRNA was noted in each sex after obstruction. A 2-fold increase in bladder nerve growth factor mRNA after obstruction was only observed in females. CONCLUSIONS: This male rat model of bladder outlet obstruction was created by placing lumen reducing ligatures at the urethrovesical junction. The dramatic increase in bladder brain derived neurotrophic factor mRNA expression and differential expression of nerve growth factor mRNA in male and female rats with bladder outlet obstruction suggest that additional neurotrophic factors may contribute to the lower urinary tract neuroplasticity associated with bladder outlet obstruction and this contribution may be gender dependent.