Answer to Question 1
Answer: Extended experience with a drug results in conditioning of environmental drug cues with the drug state. These environmental cues can elicit craving for the drug during drug abstinence. In the procedure, rats are trained to self-administer a drug for an extended period of time with each lever press accompanied by a variety of cues (pump sound, lights, and perhaps tones). The drug response is extinguished by replacing the contents of the drug syringe with salineover time the pressing ceases. On a test day, the rat receives a free-shot of the drug or experiences the drug cues. The key question is whether the drug prime or the drug cue will reinstate responding on the former drug lever.
Answer to Question 2
Answer: cannabinoid-1 (CB1)