Rats raised in an enriched condition (EC) show decreased stimulant self-administration relative to rats reared in an isolated condition (IC). However, few studies have examined the behavioral mechanisms underlying this environment-induced difference in self-administration. Because economic demand for drugs of abuse predicts addiction-like behavior in both humans and animals, we applied a behavioral economic analysis to cocaine self-administration data in EC and IC rats. During cocaine self-administration, the dose decreased across blocks of trials (0.75–0.003 mg/kg/inf), which allowed for a determination of demand intensity and demand elasticity. Demand intensity did not differ between EC and IC rats; however, cocaine was more elastic in EC rats relative to IC rats (i.e. EC rats were less willing to respond for cocaine as the unit price increased). When EC rats were placed in an isolated condition, demand elasticity decreased, whereas elasticity increased for IC rats placed in an enriched condition. Additionally, we applied behavioral economic analyses to previously published self-administration data and found that our results replicate past findings with cocaine and methylphenidate. To determine if differences in demand elasticity are specific to drug reinforcement, a separate group of rats was tested in sucrose or saccharin self-administration. Results showed that sucrose and saccharin were more elastic in EC rats relative to IC rats, and demand intensity was lower for saccharin in EC rats relative to IC rats. Overall, drug and nondrug reinforcers are more elastic in EC rats, which may account for the protective effects of environmental enrichment against stimulant self-administration.
|Number of pages||11|
|State||Published - Jan 2019|
Bibliographical noteFunding Information:
The current study was supported by NIH grants DA05312, DA12964, DA033373, and DA016176. We would like to thank Emily Denehy and Travis McCuddy for technical assistance. We would also like to thank Kristin Alvers, Dr. Thomas Green and Dr. Rebecca Hofford for allowing us to include data in the manuscript.
© 2017 Society for the Study of Addiction
- behavioral economics
- environmental enrichment
ASJC Scopus subject areas
- Medicine (miscellaneous)
- Psychiatry and Mental health