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Research Highlights

Periodically, we highlight one paper that was recently published by a Ph.D. student in the Neuroscience Institute.

Neuroscience Institute Highlighted Paper:

Jeffress EC, Huhman KL.
Copulatory and agonistic behavior in Syrian hamsters following social defeat.
Aggressive Behavior (2013) 39(3):239-45. doi: 10.1002/ab.21465. Epub 2013 Feb 4.
http://www.ncbi.nlm.nih.gov/pubmed/23382023

Stress is a pervasive problem in modern society. The most common type of stress that affects humans is social stress, which stems from conflicts with other individuals such as family members, co-workers, or peers. Unfortunately, social stress can have deleterious effects on health, including changes in weight, blood pressure, mood, and social behavior. Similar changes are found not only in humans but also in wide variety of non-human animals. Therefore, we can use animal models to improve our understanding of the neurobiological and behavioral effects of exposure to social stress.  We believe that advances in this understanding will lead to the development of new treatments to combat the deleterious effects of social stress.

The Huhman lab uses Syrian hamsters to model social stress. Syrian hamsters normally defend their home cage against intruders. After a hamster has experienced social defeat, however, they no longer defend their home cage. Instead, these previously defeated animals flee from intruders and produce only submissive and defensive behavior toward conspecifics. This dramatic behavioral change is called conditioned defeat (CD). Given that exposure to social defeat reduces plasma testosterone in a wide variety of species including humans and hamsters, and socially stressed humans often report lower sexual activity and interest, we predicted that defeated hamsters might exhibit lower sexual behavior.  Further, because exposure to receptive females can increase plasma testosterone, we also predicted that the opportunity to engage in sexual behavior after social defeat might counterbalance the effects of defeat and block the expression of CD. To our surprise, neither a single social defeat (15 min) nor exposure to repeated defeats (9, 5 min defeats) altered copulatory behavior in Syrian hamsters. Next, we demonstrated that defeated hamsters exhibited CD regardless of whether they were exposed to a receptive female after defeat. Thus, the opportunity to copulate with a female did not restore normal territorial aggression. The current data suggest that CD is not necessarily a maladaptive response to social stress, at least in terms of reproductive behavior, but that it may instead represent a viable behavioral strategy adopted by losing animals following social defeat. Further, these data indicate that CD is relatively persistent and stable, as the opportunity to copulate does not reduce the subsequent display of submissive behavior.