“…In addition, an animal's level of sucrose preference can predict its desire to self-administer cocaine (Levine et al, 2003), and sweets will reduce cocaine's reinforcing value (Comer, Lac, Wyvell, & Carroll, 1996), suggesting a relation between sweet taste and drug reward. Both obese rats and chronic drug users have low basal dopamine levels (Hamdi, Porter, & Prasad, 1992), experience periodic exaggerated dopamine release associated with either food (Fetissov et al, 2002) or drug intake (Worsley et al, 2000), and have reduced dopamine D2 receptor and increased D1 receptor expression (Fetissov et al, 2002). A number of addictive behaviors (alcoholism; cocaine, heroin, marijuana, and nicotine use; and glucose bingeing) have been associated with low expression or dysfunction of D2 receptors (Comings & Blum, 2000).…”