This project examines proneness to submissive behavior in rats and interventions to prevent its expression, by way of modeling human depression and its alleviation. Occidental Low Saccharin-consuming (LoS) rats, which are more emotionally reactive than Occidental High Saccharin-consuming (HiS) rats, more frequently become the submissive rat in the pair in a food-competition task. This suggests LoS rats have a phenotypic difference which results in both greater emotional reactivity and greater likelihood for developing depression in response to social stress. LoS rats showed a larger decrease in baseline tail skin temperature between the start of the experiment and establishment of dominant-submissive relationships, implying they experienced greater resting anxiety during competitions. Additionally, those rats that established weaker relationships also showed a larger decrease in tail skin temperature, regardless of dominant or submissive status, suggesting that anticipation of a struggle for dominant status results in greater anxiety. Increased submissiveness was correlated with a larger increase of tail temperature during a trial, suggesting that the more submissive a rat was, the more physiologically aroused it was. Furthermore, the possible acute antidepressant effects of the κ- opioid receptor antagonist nor-BNI were assessed and no significant acute antidepressant effects were found in this model.