following 4 days of treatment. Treatment of hippocampal cells in culture with 5-HT also results in the hypomethylation of the 5' CpG dinucleotide of the NGFIA consensus sequence within the exon 17 promoter of the GR gene, with no effect at the 3' site (Weaver IGC et al, unpublished results). Treatment with 8-bromocAMP produces an even more pronounced effect on cytosine methylation at the 5' CpG site. In both studies, cultures maintained under control conditions show complete methylation of both the 5' and 3' CpG sites of the NGFIA consensus sequence. Bromodeoxyuridine labeling, which marks newly generated cells, reveals little or no cell replication in the cultures at the time of 5-HT treatment. These findings reinforce the idea that the alterations in cytosine methylation occur independently of cell replication and in response to intracellular signals associated with variations in maternal care. These cells establish that 5-HT signaling induced by maternal care triggers replication-independent changes in methylation of GR exon 17 promoter through an increase in cAMP Since increased cAMP activates NGFIA, it seems that ectopic expression of NGFIA can target the demethylation process to the GR exon 17 promoter. Indeed, there is direct evidence that NGFIA can actively target methylated
