[Abstract Title]. - Society for Neuroscience

Disclosures: C.A. Fuller , None; T.M. Hoban-Higgins, None; E.S. Ingham, None; G.
Sonnenfeld, None.
Poster
280. Stress and the Brain: Stress and Neuroimmunology I
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 280.13/NN13
Topic: E.06.b. HPA axis: Brain systems and behavior
Title: Dysphoric-like behavior correlates with lack of chronic stress-induced increases in
glucocorticoids: relevance to atypical depression?
Authors: N. BOWENS, *L. JACOBSON;
Dept Pharmacol & Neurosci, Albany Med. Coll, Albany, NY
Abstract: Evidence has shown a correlation between atypical depression and abnormally low
hypothalamic-pituitary-adrenal (HPA) axis activity that may explain some symptoms of this
disorder. To develop better treatments for atypical depression, an animal model is needed to
identify causes and factors that can reverse this hypoactivity. Chronic social stress has been
reported to cause HPA hypoactivity in rats. We hypothesized that the resident intruder model
would produce similar HPA hypoactivity in mice. We placed male mice 5 minutes daily in the
home cage of another male mouse, whereas the controls were only handled. Morning
corticosterone levels were divergent enough for us to separate the intruders into two groups with
corticosterone levels at the control mean (low morning cort: LMC), and two standard deviations
above the control mean (high morning cort: HMC). Tail suspension immobility, a measure of
depression-like behavior, was significantly lower in the LMC intruders. Although this measure
suggested greater resilience, LMC mice showed other evidence of maladaptive behavior and
physiology, including increased tail suspension-induced defecation, an autonomic response to
stress, and reduced sucrose preference, a measure of depression-like anhedonia. After social
defeat, c-fos, a marker of neuronal activity, was significantly lower in the hypothalamus of HMC
versus control mice. This reduction suggests a habituation to chronic stress, which the LMC mice
did not show. Adrenocortical 11-beta hydroxylase gene expression was significantly increased in
HMC versus control mice. Overall the results show that compared to the HMC mice, the LMC
mice show reduced adrenocortical activity relative to hypothalamic activity. This hypoactivity in
the LMC mouse may prove useful in elucidating the role of HPA hypoactivity in atypical
depression.
Disclosures: N. Bowens, None; L. Jacobson , None.