GABAergic mechanisms of opiate reinforcement

The neurobiological mechanisms of opiate-induced reinforcement are still not completely understood. Over the past two decades, the vast majority of studies have focused on the role of the mesolimbic dopamine (DA) system. However, current studies strongly suggest that opiate actions on gamma-aminobutyric acid (GABA)-ergic cells in both the ventral tegmental area (VTA) and the nucleus accumbens (NAcc) appear to play critical roles. In this review, we focus on the neurochemical substrates of opiate reinforcement and review the role of DA and non-DA substrates, including opioid, GABA, glutamate and serotonin on opiate-reinforced behaviour and the activity of dopaminergic and GABAergic neurons in the VTA and the NAcc.