Repeated exposure to many drugs of abuse results in a progressive and enduring enhancement in the motor stimulant effect elicited by a subsequent drug challenge. This phenomenon, termed behavioral sensitization, is thought to underlie certain aspects of drug addiction. Behavioral sensitization is the consequence of drug-induced neuroadaptive changes in a circuit involving dopaminergic and glutamatergic interconnections between the ventral tegmental area, nucleus accumbens, prefrontal cortex and amygdala.