258— Differential response to cocaine in mice exposed to stress

Abstract

Exposure to trauma is a risk factor for substance use disorders. Using a mouse model of PTSD, we tested the effects of exposure to a stressor (synthetic fox pheromone: TMT) on response to cocaine. Cocaine induced locomotion and cocaine seeking behavior in a conditioned place preference (CPP) were assessed. TMT was an effective stressor, indicated by freezing behavior, which is a known fear response in mice. In both males and females, TMT-exposed mice showed a greater locomotor response to cocaine compared to control mice, resulting in the interaction between time and TMT treatment. TMT-exposed males, but not females, were overall more active than control mice. During CPP, female mice were first conditioned to associate one side of a 3-chambered arena with cocaine (10 mg/kg) and then tested in a 30-minute session of free exploration (15 minutes of cue-prime, 15 minutes of drug-prime). Time spent inside the drug-associated context was considered an indication of the rewarding properties of cocaine. Results indicated no group differences between female mice exposed to TMT and those that weren’t. Additionally, mice only displayed a preference for the cocaine-paired chamber during cue-primed testing. After receiving a cocaine-prime (10 mg/kg), mice did not continue this behavior

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