Renewal of drug seeking by contextual cues after prolonged extinction in rats.

Contextual stimuli associated with drug exposure can modulate various effects of drugs, but little is known about their role in relapse to drug seeking. Using a renewal procedure, the authors report that drug-associated contextual stimuli play a critical role in relapse to drug-seeking previously maintained by a heroin-cocaine mixture (speedball). Rats were trained to self-administer speedball, after which drug-reinforced behavior was extinguished over 20 days in the self-administration context or in a different context. On the test day, rats exposed to the drug-associated context, after extinction in a different context, reliably renewed drug seeking. The authors suggest that the renewal procedure can be used to study mechanisms underlying relapse to drug seeking elicited by drug-associated contextual stimuli.