E-GEOD-2870 - Transcription profiling of amaygdala, cortex and hippocampus from rats subjected to immobilization stress
Submitted on 1 July 2005, released on 31 July 2007, last updated on 10 June 2011
Prolonged stress has adverse consequences for neurons in the hippocampus (HIPP). The amygdala (AMY) is a brain region that is similar to HIPP across many measures, suggesting that chronic stress might modulate AMY and HIPP function in similar ways. However, studies addressing this issue have produced surprising results. For example, a regimen of chronic stress shown to produce atrophy in HIPP neurons caused dendritic branching in AMY neurons. These and other data have revealed that excessive stress induces fundamentally opposing processes in the AMY and HIPP, such that AMY function is facilitated by levels of stress that produce deleterious effects in HIPP. The mechanisms that contribute to the opposing responses of these brain regions to chronic stress are unknown. Such knowledge may suggest novel directions for pharmacological interventions to protect the HIPP from stress-mediated damage.,We will determine gene expression patterns in the hippocampus and amygdala under basal and stressful conditions, with a particular interest in those genes that are differentially regulated across the two regions. ,We hypothesize that genes that are oppositely regulated in the amygdala and hippocampus after stress mediate the opposing functional consequences of chronic stress in these two brain regions. Moreover, genes which are differentially expressed in these regions under basal conditions may underlie the distinct responses of these regions to stress.,Rats will receive either 30sec of handling (Control group; n=15) or 3hr of immobilization stress (Stress group; n=15) each day for 14 consecutive days. This stress paradigm has previously been shown to produce opposing effects on dendritic morphology and region-dependent behaviors for the hippocampus versus amygdala. Twenty-four hours after the last stress or handling session, the rats will be overanaesthetized, and the brain will be removed and placed in ice-cold buffer. Tissue will be rapidly dissected from the basolateral complex of the amygdala and the CA3 region of the hippocampus of both hemispheres, flash frozen in liquid nitrogen, and stored at -80C until further processing. The tissue from each brain region will be pooled across groups, yielding four samples (Control-Hippocampus, Control-Amygdala, Stress-Hippocampus, and Stress-Amygdala). Total RNA will be extracted using standard methods, and sent to the centers. Each sample will be run in triplicate, utilizing a total of 12 Affymetrix Rat Genome U34A gene chips. A triplicate array assay of pooled samples has previously been shown to both substantially increase the sensitivity of detecting genes of interest and reduce the variability associated with individual microarrays. In addition, the large number of rats used in each group will reduce the variability in gene expression associated with individual responses to chronic stress, as well as variability due to slight anatomical differences in the tissue extracted from each rat.
transcription profiling by array, co-expression, organism part comparison, stimulus or stress