The mesolimbic dopamine (DA) system consists of projections from the ventral tegmental area (VTA) to the nucleus accumbens (NAcc) and mediates in part the motor-stimulatory and reinforcing effects of drugs of abuse (Nestler 2004; Wise 2004; Bjorklund and Dunnett 2007). Though drugs of abuse have distinct molecular targets, they share the ability to increase DA levels in the NAcc (Luscher and Ungless 2006). Cocaine, for example, elevates NAcc DA levels by blocking the re-uptake of released DA. The physiological relevance of this effect and location is underscored by the impact of destruction of the dopaminergic projection from the VTA to NAcc, which includes hypoactivity and insensitivity to the motor-stimulatory effects of cocaine (Koob et al. 1981).
