Music-induced context preference following cocaine conditioning in rats

Traditional models of drug-seeking behavior have shown that exposure to associated environmental cues can trigger relapse. These learned associations take place during repeated drug administration, resulting in conditioned reinforcement. Although considerable investigation has occurred regarding simple conditioned stimuli, less is known about complex environmental cues, particularly those that may be salient in human addiction. Recent studies indicate that music can serve as a contextual conditioned stimulus in rats and influence drug-seeking behavior during abstinence. The purpose of the present study was to further assess the effectiveness of music as a conditioned stimulus in rats, to determine rats' preferences for two contrasting pieces of music, and to determine rats' preferences for music versus silence. To this end, we created an apparatus that gave instrumental control of musical choice (Miles Davis vs. Beethoven) to the rats themselves. After determining baseline musical preference, animals were conditioned with cocaine (10 mg/kg) to the music they initially preferred least, with alternating conditioning sessions pairing saline with the music preferred most. The animals were subsequently tested in a drug-free state to determine what effect this conditioning had on musical preference. The results indicate that music serves as an effective contextual conditioned stimulus, significantly increasing both musical preference and locomotor activity after repeated cocaine conditioning. Furthermore, we found that rats initially favor silence over music, but that this preference can be altered as a result of cocaine-paired conditioning. These findings demonstrate that, after repeated association with reward (cocaine), music can engender a conditioned context preference in rats; these findings are consistent with other evidence showing that musical contextual cues can reinstate drug-seeking behavior in rats.