Developmental expression of urinary bladder neurotrophic factor mRNA and protein in the neonatal rat

These studies were performed to determine the developmental expression patt ern of neurotrophic factor (beta NTF): nerve growth factor (beta NGF), brai n-derived neurotrophic factor (BDNF), glial-derived neurotrophic factor (GD NF), ciliary neurotrophic factor (CNTF), neurotrophin-3 (NT-3) and NT-4 mRN A and NGF, NT-3 and NT-4 protein in the urinary bladder of the postnatal Wi star rat. It was hypothesized that NTFs may contribute to the development o f the spinobulbospinal micturition reflex that represents the adult micturi tion pattern. Changes in NTF mRNA or protein expression in the urinary blad der at the time of development of the mature micturition reflex (postnatal days (P) 16-18) may suggest an involvement of target-derived NTFs in this m aturation process. Developmental ages, prior to (P5, PIG, P15) or following (P20, P30, adult P90) the development of the spinobulbospinal micturition reflex were selected and the urinary bladder was analyzed for levels of neu rotrophic factor mRNA or protein. Results from ribonuclease protection assa ys demonstrated a similar developmental pattern among each neurotrophic fac tor examined. Neurotrophic factor mRNA levels increased by P10 and reach a maximum by P15. Subsequently, NTF mRNA levels declined to adult levels that were less than the earliest postnatal time examined (P5). NTF mRNA express ion was significantly (p less than or equal to 0.05-0.001) greater at P10, P15, P20 and P40 (NT-4 mRNA) compared to adult levels for each NTF examined except GDNF mRNA. In general, NGF, NT-3 and NT-4 urinary bladder protein l evels in early postnatal development, as determined by ELISA, were similar when compared to the corresponding mRNA expression. Differences in the corr elation between NT-3 and NT-4 mRNA and protein expression were demonstrated in the adult urinary bladder where significantly (p less than or equal to 0.001) greater levels of protein were revealed despite relatively low abund ance of NT-3 and NT-4 mRNA. The developmental expression pattern (maximum e xpression at the second to third postnatal week) of NTFs in the urinary bla dder is consistent with a potential role in the development of the spinobul bospinal reflex. Relatively high expression of NT-3 and NT-4 protein in the adult urinary bladder suggests a potential importance of these factors in the adult lower urinary tract. (C) 2000 Elsevier Science B.V. All rights re served.