Lateralized amygdala activation: Importance in the regulation of anxiety and pain behavior

Background: The amygdala is involved in the emotional responses to fear including anxiety and heightened pain reporting. In a rodent model, bilateral activation of the central amygdala (CeA) with corticosterone (CORT) produces anxiety-like behavior, somatic allodynia and visceral hypersensitivity. Although hemisphere-specific processing differences between the left and right amygdala have been reported, it remains unclear whether the right or left CeA is involved in the production of anxiety-like behavior, and abnormal somatic and visceral perception. The goal of the present study was to investigate the hypothesis that lateralized corticoid-mediated mechanisms in the CeA produce anxiety as well as abnormal pain perception. Methods: Anesthetized rats received stereotaxic implants of cholesterol (Choi; 30 mu g) or CORT (30 mu g) micropellets onto the left, right or both dorsal margins of the CeA. Following implantation (5-7 days), anxiety-like behavior was assessed on the elevated plus-maze (EPM), somatic allodynia was measured using Von Frey filaments, and visceral sensitivity was quantified as a visceromotor response (VMR) to colorectal distention (CRD) at 0-60 mm Hg. Results: Unilateral implants of CORT onto either the left or right CeA produced anxiety-like behavior and somatic allodynia. However, our data illustrated that the bilateral placement of CORT onto the CeA was required to increase visceral sensitivity. Conclusion: These results provide evidence that there is no hemispheric lateralization of the CeA involved in corticoid-mediated anxiety-like behavior and heightened pain reporting. Published by Elsevier Inc.