The Effects of Cocaine-paired Contextual Stimuli on Impulsive Decision Making in Rats (2012)

Undergraduates: Antonia Bista, Xiaohu Xie

Faculty Advisor: Xiaohu Xie
Department: Psychology & Neuroscience

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Chronic cocaine exposure creates unconditioned enhancement in impulsive decision making; however, little is known about the effects of cocaine-paired conditioned stimuli on this behavior. This study explored the effects of cocaine-paired contextual stimuli on impulsive decision making using the delay discounting task in rats. The delay discounting task consisted of lever press-based choices between a single food pellet (small reward) available immediately and three food pellets (large reward) available after a 10-, 20-, 40-, or 60-s time delay. After rats (N=8) were trained to achieve a stable performance on this task in a neutral context, they received Pavlovian context-cocaine (15mg/kg, IP) and context-saline (1 ml/kg, IP) pairings in two distinctly different contexts over 14 days. On subsequent test days, delay discounting performance was assessed in the previously cocaine-paired or the saline-paired context following pretreatment with saline or cocaine, using a counterbalanced within-subjects testing design. Cocaine conditioning failed to alter delay discounting in the neutral context. Without cocaine pretreatment, cocaine conditioning produced a greater decrease in preference for the large reward as a function of delay duration in the cocaine-paired context, relative to the saline-paired context. These results suggested that exposure to the previously cocaine-paired context evokes a state of impulsive decision making, which may facilitate drug relapse in cocaine users.