BDNF and Mental deterioration: However, our previous study showed that cognitive decline in rats with pinealectomy in 14-month-old rats correlated with reduced BDNF/ERK1/2/CREB signaling in some regions of the hippocampus, while ERK 1/2 and its phosphorylated form were increased in the other areas compared to the matched sham group, suggesting that melatonin-associated changes in this age are complex.