Funding: USPHS/NIDA grants R01 DA015449, R01 DA020669, and T32 DA007267.
Individual differences in discount rate are associated with demand for self-administered cocaine, but not sucrose
Article first published online: 4 AUG 2011
© 2011 The Authors, Addiction Biology © 2011 Society for the Study of Addiction
Volume 18, Issue 1, pages 8–18, January 2013
How to Cite
Koffarnus, M. N. and Woods, J. H. (2013), Individual differences in discount rate are associated with demand for self-administered cocaine, but not sucrose. Addiction Biology, 18: 8–18. doi: 10.1111/j.1369-1600.2011.00361.x
- Issue published online: 25 DEC 2012
- Article first published online: 4 AUG 2011
- Behavioral economics;
- cocaine demand;
- delay discounting;
- impulsive choice;
- Sprague Dawley rats
Substance abusers, including cocaine abusers, discount delayed rewards to a greater extent than do matched controls. In the current experiment, individual differences in discounting of delayed rewards in rats (choice of one immediate over three delayed sucrose pellets) were assessed for associations with demand for either sucrose pellets or an intravenous dose of 0.1 mg/kg/infusion cocaine. Twenty-four male Sprague Dawley rats were split into three groups based on sensitivity to delay to reinforcement. Then, demand for sucrose pellets and cocaine was determined across a range of fixed-ratio values. Delay discounting was then reassessed to determine the stability of this measure over the course of the experiment. Individual differences in impulsive choice were positively associated with elasticity of demand for cocaine, a measure of reinforcer value, indicating that rats having higher discount rates also valued cocaine more. Impulsive choice was not associated with the level of cocaine consumption as price approached 0 or with any parameter associated with demand for sucrose. Individual sensitivity to delay was correlated with the initial assessment when reassessed at the end of the experiment, although impulsive choice increased for this cohort of rats as a whole. These findings suggest that impulsive choice in rats is positively associated with valuation of cocaine, but not sucrose.