Repeated exposures intensify rather than diminish the rewarding effects of amphetamine, morphine, and cocaine
✍ Scribed by Bow Tong Lett
- Publisher
- Springer
- Year
- 1989
- Tongue
- English
- Weight
- 743 KB
- Volume
- 98
- Category
- Article
- ISSN
- 0033-3158
No coin nor oath required. For personal study only.
✦ Synopsis
It is commonly believed that repeated exposures diminish the pleasurable effects of drugs and hence that pleasure must have only a minor role in addiction. In six experiments with rats, repeated exposures to amphetamine, morphine, or cocaine were found to enhance the drug-induced rewarding effect as measured by conditioned place preference. Thus, sensitization to the rewarding effect, rather than tolerance, was obtained. Also, cross-sensitization was obtained; exposures to amphetamine enhanced the rewarding effect of morphine and vice versa; similarly, exposures to morphine enhanced the rewarding effect of cocaine. These findings support a new theory: drugs of abuse are addictive because repeated exposures sensitize the central reward mechanism so that drug taking produces a progressively greater reinforcing effect each time it occurs.