Metabolic and endocrine consequences of social stress in a visible burrow system.

The visible burrow system (VBS) is an ethologically relevant model of social stress, which has been used to study the aggression of male rats in a social context. Previous studies using the VBS have established physiological, endocrine, and neurochemical characteristics associated with chronic social stress in dominant and subordinate animals. A critical criterion in establishing an animal model for research is the replication of findings and the independent validation of the model. Here, we independently confirm previously reported findings and include novel control groups that are important in dissociating the effects of chronic social stress from those resulting from group-housing the male rats in an "enriched environment". Furthermore, we show that whereas the VBS model is useful for males, it is not effective for studies of females because they do not form dominance hierarchies when housed in groups. We also extend the use of the VBS model to examine the etiology of stress-induced anorexia and obesity, finding that weight loss in subordinate rats is attributable to decreased adipose and lean tissue, whereas in dominant rats, it is associated only with adipose tissue loss. Consistent with this, the adiposity hormones leptin and insulin are decreased in subordinates and, to a lesser extent, in dominants, compared with the controls. In summary, the VBS model of chronic social stress is an ethologically relevant animal model and provides a valuable tool for studies of stress-related conditions and pathologies.