Abstract: Second-order schedules, which are called second-order schedules of drug self-administration when put into experiments, stress the significance of the conditioned stimuli in the acquiring and keeping of the behavior that takes place in this model. Under the influence of conditioned stimuli, animals press a lever to seek drugs. The results of many studies suggest that nucleus accumbens core, basolateral amygdale and medial prefrontal cortex play an important role in the drug-seeking behavior aroused by conditioned stimuli. The use of second-order schedules makes it possible to predict substance that may result in addiction, which also provides new ideas in preclinical testing of potential treatment strategies for drug addiction

Key words: second-order schedules, drug-addiction, conditioned stimuli, drug seeking