Acute early life stress (ELS) has major behavioral and physiological implications later in life in mammals. In past experiments, the focus has been on chronic and not acute early life stressors. The literature is growing regarding the effects of ELS on drug-taking behavior later in life in both humans and rodent models. There is increased interest in studying the effects of ELS on sensitization to psychostimulants, and the cross-sensitization to other drugs of abuse. Additionally, females are more vulnerable to the impacts of early life stress and exposure to drugs of abuse. To investigate these questions, we used 68 Long-Evans rats (36 males; 32 females) that were given footshocks for ELS, conditioned place preference (CPP) for reward learning, and locomotor sensitization with amphetamine for drug sensitization (and morphine to test for cross-sensitization). Based on preliminary findings, we expect that acute ELS will sex-dependently alter learning with both natural and drug reinforcers. We expect to see females exposed to ELS will not develop CPP, while males exposed to ELS will. ELS will increase locomotor sensitization to amphetamine in females, but not in males. Finally, ELS will increase morphine/amphetamine cross-sensitization in females, but not in males. This research will provide novel contributions to the literature by showing that acute exposure to ELS leads to long-term consequences on these learning processes, and the sex-dependent effect would further validate our animal model since most animal models of ELS do not show sex-dependent effects, while human drug users show female vulnerability. After completion of the study, future directions could look into different classes of drugs and varying behavioral studies that would contribute to the understanding of drug effects and their relation to ELS. This research has allowed us to work as a team and build up crucial research skills to use in future careers.
Authors: Ellie Abrams, Katherine Block, Emily Manasian, Logan Warner, Lydia Yamashiro
Faculty Advisors: Jennifer Quinn, Psychology
Graduate Student Advisor: Brianna Minshall, Psychology
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