Modulation of different states of anxiety-like behavior by chronic stress.

Recent studies have identified putative cellular correlates of stress-induced amygdalar plasticity underlying anxiety-like behavior. Chronic immobilization stress (CIS), but not chronic unpredictable stress (CUS), has been reported to induce dendritic remodeling in the basolateral amygdala (BLA). The BLA is also important for consolidation of anxiety in the elevated plus-maze, which is manifested as increased open-arm avoidance on reexposure to the maze. The authors found that CIS, unlike CUS, facilitated anxiety-like behavior in the plus-maze, and this occluded further increase in anxiety when CIS rats were reexposed to the maze 72 hr after the first trial. However, both CUS and control rats exhibited consolidation between trials. Thus, consolidation of anxiety may share common cellular mechanisms that also underlie chronic stress-induced structural plasticity in the amygdala.