The neurotransmitter system that has been most-clearly identified with the habit-forming actions of drugs-of-abuse is the mesolimbic dopamine system, with its efferent targets in the nucleus accumbens and its local GABAergic afferents. The reward-relevant actions of amphetamine and cocaine are in the dopaminergic synapses of the nucleus accumbens and perhaps the medial prefrontal cortex.
The neural pathway most directly implicated in the addictive effects of substance-abuse drugs is the mesolimbic dopamine system, which includes its output targets in the nucleus accumbens and local inhibitory inputs. The actions that trigger reward from amphetamine and cocaine occur in the dopaminergic connections of the nucleus accumbens and possibly the medial prefrontal cortex.