AGE-RELATED PRODUCTION OF NEW GRANULE CELLS IN THE ADULT DENTATE GYRUS

UNLIKE most neurones, the dentate granule cells continue to be produce d in adults. Recently our study has demonstrated that a highly polysia lylated neural cell adhesion molecule (NCAM-H) is reliable molecular m arker for newly generated and developing dentate granule cells. Here w e examined age-related changes in the number of newly generated and de veloping granule cells. In rats injected with 5-bromo-2'-deoxyuridine (BrdU), a thymidine analogue, at 35 days to 18 months of age, double i mmunohistochemistry for BrdU and NCAM-H showed that the numbers of NCA M-H-positive and BrdU-/NCAM-H-positive granule cells gradually decreas ed over more than one year, but they were still detected in 18-month-o ld rats. These findings indicate that newly formed and developing gran ule cells occur in the dentate gyrus of young and aged rats, but the n umber of these cells decreases with age.