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Drug versus sweet reward: greater attraction to and preference for sweet versus drug cues
Author(s) -
Madsen Heather B.,
Ahmed Serge H.
Publication year - 2015
Publication title -
addiction biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.445
H-Index - 78
eISSN - 1369-1600
pISSN - 1355-6215
DOI - 10.1111/adb.12134
Subject(s) - lever , psychology , conditioned place preference , conditioning , classical conditioning , addiction , nucleus accumbens , heroin , drug , pharmacology , neuroscience , dopamine , medicine , psychiatry , statistics , physics , mathematics , quantum mechanics
Despite the unique ability of addictive drugs to directly activate brain reward circuits, recent evidence suggests that drugs induce reinforcing and incentive effects that are comparable to, or even lower than some nondrug rewards. In particular, when rats have a choice between pressing a lever associated with intravenous cocaine or heroin delivery and another lever associated with sweet water delivery, most respond on the latter. This outcome suggests that sweet water is more reinforcing and attractive than either drug. However, this outcome may also be due to the differential ability of sweet versus drug levers to elicit P avlovian feeding‐like conditioned responses that can cause involuntary lever pressing, such as pawing and biting the lever. To test this hypothesis, rats first underwent P avlovian conditioning to associate one lever with sweet water (0.2% saccharin) and a different lever with intravenous cocaine (0.25 mg) or heroin (0.01 mg). Choice between these two levers was then assessed under two operant choice procedures: one that permitted the expression of P avlovian‐conditioned lever press responses during choice, the other not. During conditioning, P avlovian‐conditioned lever press responses were considerably higher on the sweet lever than on either drug lever, and slightly greater on the heroin lever than on the cocaine lever. Importantly, though these differences in P avlovian‐conditioned behavior predicted subsequent preference for sweet water during choice, they were not required for its expression. Overall, this study confirms that rats prefer the sweet lever because sweet water is more reinforcing and attractive than cocaine or heroin.