 Addictive drugs and behaviors are rewarding and reinforcing (i.e., are "addictive") due to their effects on the dopamine reward pathway.The lateral hypothalamus and medial forebrain bundle has been the most-frequently-studied brain-stimulation reward site, particularly in studies of the effects of drugs on brain stimulation reward.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.