Furthermore, infusions of a DNA methyltransferase inhibitor, zebularine, significantly induced bdnf DNA demethylation and were sufficient to increase mRNA levels of bdnf in the hippocampus. Consistent with this finding was the discovery that when long-term memory formation was blocked by the NMDA receptor use-dependent antagonist MK801, bdnfDNA methylation as well as bdnfgene expression was altered in the hippocampus, leading to a deficiency in memory formation .