The goals of the proposed research are to (1) determine the extent to which cocaine-taking history affects the reinforcing strength of cocaine, (2) to determine the extent to which cocaine-taking history affects the reinforcing strength of food, and (3) to determine the degree to which a long cocaine history causes compulsive cocaine use. The first of the proposed experiments will examine the effects of cocaine history on the reinforcing strength of cocaine. This will be accomplished by assigning two groups of animals to a short or long history (determined by the number of sessions) of cocaine self-administration. Following the respective history of each group, the elasticity of demand for cocaine will be measured using a demand curve where the number of earned cocaine reinforcers will be plotted as a function of cocaine's price (the number of responses required for a single cocaine reinforcer). Demand analysis is used because it is to date, the most valid assay for quantifying the reinforcing strength of a given reinforcer. The second experiment will examine the effects of a long cocaine self-administration history on the elasticity of food demand using a procedure similar to that described for Exp. 1 except that following the drug history, the elasticity of food will be assayed. A third experiment will be performed to determine the degree to which a long cocaine history causes compulsive use of cocaine that leads to the loss of a natural reinforcer (food). This will be accomplished by comparing the number of cocaine and food reinforcers chosen within a discrete trials, mutually-exclusive choice procedure. The results from these experiments could provide profound insight into the processes underlying drug addiction, namely, the capacity for addictive drugs such as cocaine to increase in their reinforcing strength with increased drug use and the capacity for natural rewards such as food to decrease in their rewarding strength with increased drug use. In addition, the proposed work could provide a model showing the capacity of addictive drugs to increase compulsive drug with increased drug experience at the expense of serious negative consequences, such as the loss of food. Altogether, such findings will be important for the further study of behavioral and neurobiological variables involved in producing drug addiction and for the development of treatments for this disease.
| Marks, Katherine R; Kearns, David N; Christensen, Chesley J et al. (2010) Learning that a cocaine reward is smaller than expected: A test of Redish's computational model of addiction. Behav Brain Res 212:204-7 |
| Christensen, Chesley J; Kohut, Stephen J; Handler, Samantha et al. (2009) Demand for food and cocaine in Fischer and Lewis rats. Behav Neurosci 123:165-71 |
| Christensen, Chesley J; Silberberg, Alan; Hursh, Steven R et al. (2008) Demand for cocaine and food over time. Pharmacol Biochem Behav 91:209-16 |
| Christensen, Chesley J; Silberberg, Alan; Hursh, Steven R et al. (2008) Essential value of cocaine and food in rats: tests of the exponential model of demand. Psychopharmacology (Berl) 198:221-9 |
