The role of heritable phenotype and social environment on fear extinction learning in rats
Prater KE, Aurbach EL, Larcinese HK, Blandino P, Watson SJ, Maren S, Akil H
Society for Neuroscience. 2016.
Heritable propensities, such as temperament, that promote vulnerability or resilience in certain individuals are likely to interact with environmental factors (like trauma) to predict the development of PTSD. However, we know little about these interactions in humans or in animal models. The social buffering hypothesis posits that social support can mediate the effects of stress on an individual. We manipulated the social environment of rats to examine whether this variable would affect extinction behavior in male outbred and selectively bred animals. We compared outbred Sprague Dawley rats to rats selectively bred for high (bHR) or low (bLR) locomotor response to a novel environment. We demonstrated that the heritable phenotype of selectively bred animals leads to stable differences in fear extinction behavior across generations, indicating that these differences are similar to “genetic” propensities. We also observed that social environment significantly influenced the extinction learning of both outbred and selectively bred rats. We then manipulated the locomotor phenotype of the selectively bred animals through selective breeding and observed the interaction of this change in their heritable phenotype with the social environment. We found evidence that manipulating both the heritable locomotor phenotype and the social environment of selectively bred rats leads to additive effects, demonstrating a possible gene-by-environment interaction between novelty-seeking phenotype and social environment during extinction learning. Our work provides strong evidence that social environment significantly affects the extinction of learned fear in outbred and selectively bred rats, and has implications for both experimental design considerations and developing further understanding of gene-by-environment interactions in animal models.