Time-Dependent Effects of Stress on Cocaine Conditioned Place Preference Using a Rat Model of Posttraumatic Stress Disorder

Posttraumatic Stress Disorder (PTSD) affects approximately 8% of the entire population within their lifetimes. A startling trend of co-occurring PTSD and cocaine use has surfaced among humans who express these disorders. The present study employed the rat model of PTSD, Single Prolonged Stress, to examine the effects of stress on the rewarding properties of cocaine. Place conditioning was used to specifically evaluate differences between animals that had undergone a post-stress delay of conditioning in comparison to animals that were not delayed. This delay before conditioning, or incubation period, is a time spent undisturbed in the home cage for 10-days post-stress and has been implicated as the phase in which many of the physiological, neurochemical and behavioral changes observed in humans who have experienced stress take place. Although cocaine conditioned place preference was observed, no significant differences were detected between animals that were not stressed, stressed but not incubated, or stressed and then incubated. These results suggest that it is possible that the changes that are understood to take place within this incubation period did not directly influence cocaine reward, or that they did not take place. Future work should focus on examining different drugs, in addition to including additional testing intervals, and varying drug dose