In relation to PPARγ it has been recently demonstrated that this receptor is present in the VTA, where it co-localizes with tyrosine hydroxylase (TH), suggesting its expression in dopaminergic cells (30). The VTA dopamine system has a well established role in several aspects of drug dependence including sensitization, drug intake and relapse, which may explain the findings with alcohol, methamphetamine and heroin reviewed above. In this respect, recent data from our laboratory demonstrated that activation of PPARγ by pioglitazone reduced morphine-induced increases in the firing rate of VTA dopamine cells and dopamine release in the shell portion of the nucleus accumbens.
