Abstract

Introduction: The basolateral amygdala (BLA) is implicated in stress-related disorders such as anxiety-like behavior. Substantial data exist demonstrating a close relationship between anxiety and adrenergic receptor function in patients with anxiety disorders; however, little is known about the effects of the beta 1 adrenergic receptor in the BLA on anxiety. This experiment examined the effects of the beta 1 adrenergic receptor in the BLA on anxiety-like behavior. Methods: Male Wistar rats were exposed to foot-shock stress four consecutive days that were uncontrollable. The beta 1-adrenoreceptor agonist (dobutamine; 0.5 mu l/side) or antagonist (atenolol; 0.25 mu l/side) bilaterally infused into the BLA five minutes before foot-shock stress. Anxiety-like behaviors were assessed 24h after four consecutive day's uncontrollable stress using elevated plus-maze (EPM) and open field test (OFT). Results: Findings of EPM revealed that foot-shock stress leads to anxiogenic effect with reduction the time spent and the number of entries into the open arms and increased head-dipping. Intra-BLA infusions of atenolol before stress affected animal behavior differently, such that it significantly increased the time spent and the number of entries into the open arms and decreased head-dipping. Also, OFT results showed the intra-BLA infusion of atenolol increased the time periods spent in the center, number of center entries and reduced the number of rearing as compared with the stress group. Conclusion: These results suggest that the anxiety-like behavior observed after the foot-shock stress is mediated, in part, by exaggerated beta 1 adrenergic receptor acting at the BLA.