This study investigated the effects of neonatal hyperoxia (high oxygen exposure) on neurotrophin gene expression in mice. The researchers found that hyperoxia induced alterations in brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) mRNA expression levels in the isocortex and prefrontal cortex. Specifically, BDNF mRNA expression decreased in the prefrontal cortex but increased in the isocortex, while GDNF mRNA expression increased in both regions following hyperoxia. Hyperoxia also altered mRNA expression levels of DNA methyltransferases DNMT1 and DNMT3a, which regulate neurotrophin gene expression through DNA methylation. These results suggest that neonatal