Decreased methylation of the NK3 receptor coding gene (TACR3) after cocaine-induced place preference in marmoset monkeys.

Epigenetic processes have been implicated in neuronal plasticity following repeated cocaine application. Here we measured DNA methylation at promoter CpG sites of the dopamine transporter (DAT1) and serotonin transporter (SERT) and neurokinin3-receptor (NK3-R)-receptor (TACR3) coding genes in marmoset monkeys after repeated cocaine injections in a conditioned place preference paradigm. We found a decrease in DNA methylation at a specific CpG site in TACR3, but not DAT1 or SERT. Thus, TACR3 is a locus for DNA methylation changes in response to repeated cocaine administration and its establishment as a reinforcer, in support of other evidence implicating the NK3-R in reinforcement- and addiction-related processes.