[The role of CC-chemokine ligand 2 in the development of psychic dependence on methamphetamine].

Addiction is described as a chronic neurological disorder associated with plasticity in the mesolimbic system. Recently, it has been suggested that neuroinflammation plays an important role in the induction of neuronal plasticity and the formation of pathogenesis in chronic neurological disorders. Therefore, we examined the role of CC-chemokine ligand 2 (CCL2), a proinflammatory chemokine, in the development of psychic dependence on methamphetamine. In mice treated with methamphetamine, CCL2 mRNA was significantly increased in prefrontal cortex and nucleus accumbens. Moreover, phosphorylated tyrosine hydroxylase serine40 (pTH Ser40) levels in the ventral tegmental area (VTA) were increased by methamphetamine. Similarly, pTH Ser40 levels in the VTA were also increased by the intracerebroventricular administration of recombinant CCL2. The increment of pTH Ser40 levels in the VTA by methamphetamine was attenuated by RS504393, a selective CC-chemokine receptor 2 (CCR2) antagonist, indicating that the increased CCL2 activates the brain reward system via CCR2 activation. In the conditioned place preference test, methamphetamine produced place preference in a dose-dependent manner, which was attenuated by RS504393. These results suggest that the activation of the brain reward system via CCL2-CCR2 pathway plays an important role in the development of psychic dependence on methamphetamine.