Individual differences in rats selectively bred for locomotor response to a novel environment affect fear conditioning and extinction behavior
Prater KE, Aurbach EL, Larcinese H, Blandino P, Watson SJ, Maren S, Akil H
Society for Neuroscience. 2013.
Understanding why certain individuals succumb to PTSD while others remain resilient following trauma is crucial for the development of novel treatments for anxiety. Here, we used selectively bred animals to determine whether individual differences in baseline anxiety might influence vulnerability to maladaptive fear. Thirty-two rats selectively bred for high (bHR) or low (bLR) locomotor response to a novel environment and 16 rats from the F1 generation of a bHR-bLR cross (bIRs) which display an intermediate locomotor phenotype were used in this study. In a separate study, 48 outbred Sprague-Dawley rats were also fear conditioned for comparison to the selectively bred rats. During conditioning, rats received 5 tone (80dB, 2 kHz, 10s) - shock (0.6mA, 2s) pairings in a novel environment. Twenty-four hours later, rats either received 45 tones in the absence of shock (extinction), or no stimuli (no-extinction) in a different novel environment. Extinction retention was tested 24 hours later with the presentation of an additional 45 tones. bLRs and bIRs demonstrated significantly higher freezing than bHRs during conditioning. bIRs and bLRs show no differences in freezing behavior compared to the outbred rats. Despite differences in freezing behavior, bHRs and bLRs show no differences in fecal output or cortisol levels after fear conditioning indicating equal levels of experienced fear. bLRs show decreased extinction and extinction retention than bIRs and bHRs, while bHRs show faster extinction and greater retention than bIRs. These results indicate that rats selectively bred for differences in locomotor response to a novel environment may provide a good model for developing understanding of underlying differences in vulnerability to maladaptive fear.