Potential role of anxiety and stress in aggressive behavior in rats (839.2)

Abstract

The social defeat paradigm involves aggressive encounters by a large Long‐Evans (LE) male rat (resident) toward a smaller Sprague‐Dawley (SD) male rat (intruder). Successful application of chronic social defeat stress to SD rats is dependent upon appropriate selection of LE rats with consistent levels of aggressive behaviors, as determined from the 3‐d screening process. During screening for the aggressor LE rats, we observed that half of all screened LE rats did not reach the criterion for aggression (LE rats performing a defeat, characterized by the intruder surrendering or acquiring a supine position for at least 3 sec). This difference in aggression between age and weight matched LE rats was startling and led us to the present study. Herein, we measured behavioral differences between the two groups of LE rats (aggressors and non‐aggressors). We analyzed their anxiety‐like behavior using open‐field and elevated plus maze tests. We also examined aggressive behavior in the two groups. (Aggression was measured by recording time taken to defeat the intruder SD rat and time taken to attack a novel object. We observed a significant increase in anxiety‐like behavior in aggressor rats when compared to the non‐aggressive group. Furthermore, time taken to defeat the intruder rat and to attack a novel object was significantly lower in aggressive LE rats. Biochemical data suggests occurrence of significant differences in the levels of stress (assessed via corticosterone assay) and oxidative stress (analyzed via 8‐isoprostane and protein carbonylation) in rats associated with aggressive and non‐aggressive behaviors.Grant Funding Source: NIH‐R15‐G103327