Fig. 1.

Reward circuit (schematic), including dopamine neurons in the VTA projecting to “reward neurons” in the NAc. The NAc is divided into the core (C) and the shell, which is subdivided into ventral (V), medial (M), and dorsal (D) parts. The reward system is affected by most categories of drugs of abuse and involves numerous transmitters in the two main regions. The extended amygdala, not shown for simplicity, is sometimes considered part of the circuit. Color code: red, dopamine; violet, glutamate; blue, GABA. Acetylcholine, 5-hydroxytryptamine (5HT), and cannabinoid cells are not shown. Receptors are indicated for N (brown, nicotine and nicotinic acetylcholine receptor), O (yellow, opioid peptides and opiate drug receptor), and the orange ball (cocaine sites on dopamine transporter on dopamine nerve endings); BZ (sites implicated for the action of benzodiazepines on GABA interneurons in VTA) (16); and EtOH (sites implicated for action of EtOH). The author acknowledges input to this figure (17–19).