The role of basolateral amygdala in the regulation of stress-induced phosphorylated extracellular signal-regulated kinase expression in the hippocampus.

Previous studies have shown that the amygdala plays a key role in the modulation of uncontrollable stress effect on hippocampal long-term potentiation and memory in rats. This study aimed to determine the effects of selective neurotoxic lesions of the basolateral amygdala (BLA) on stress-induced glucocorticoid receptor (GR) translocation and alteration of phosphorylated extracellular signal-regulated kinases (pERK) in the hippocampus. Intrinsic neurons of the BLA in rats were destroyed using N-methyl-d-aspartate and the rats were subjected to uncontrollable stress induced by restraint and electrical tail shocks. Western blot analyses showed that stress-induced GR translocation occurred in both rats with sham-operated surgery and rats with BLA lesions. As in the Western blot analyses, immunohistological analyses revealed stress-induced reduction of GR expression in CA1 and dentate gyrus (DG) of the hippocampi in control rats and rats with BLA lesions. In addition, the Western blot analyses showed that, in response to stress, the levels of hippocampal pERK were reduced in the sham-operated controls, but not in the rats with BLA lesions. Interestingly, the immunohistological analyses showed that BLA lesions prevented the stress-induced reductions in hippocampal pERK levels, only in the DG. These results suggested that the amygdala modulates stress-induced cognitive impairments by regulating the ERK signaling pathway in the hippocampus.