The interrelationship between BDNF and its precursor and the level of active caspase-3 in the brain regions of neonatal rats

Brain-derived neurotrophic factor (mat-BDNF) promotes neuronal survival, whereas its precursor protein (pro-BDNF) induces cell death, which indicates the opposite but potentially important roles of both forms of this neurotrophin in brain development. We studied the contents of mat- and pro-BDNF and active caspase-3 in the brain regions of 8-day-old rat pups. Taking the level of caspase-3 in the cerebral cortex into account we may conclude that intense apoptosis occurs in this structure; however, the ratio of mat-BDNF to pro-BDNF in this region was the lowest among all structures studied. In contrast, in the brainstem of neonatal rats, where processes of cell proliferation and elimination are completed, the mat-BDNF/pro-BDNF ratio was substantially higher compared to the cortex. The mat-BDNF/pro-BDNF ratio in the cerebellum and hippocampus also supports the inverse relationship between this index and the level of active caspase-3 in different brain regions. Our data suggest that both forms of BDNF are involved in the determination of cell fate in the developing brain.