beta 1-and beta 2-Adrenoceptors in Basolateral Nucleus of Amygdala and Their Roles in Consolidation of Fear Memory in Rats

It is known that P-adrenoceptor (AR) in the basolateral nucleus of amygdala (BLA) plays an essential role in fear memory formation. However, the cellular and subcellular distributions of beta 1- and beta 2-ARs in the BLA and their roles in fear memory formation are poorly understood. Here, we report that both beta 1- and beta 2-ARs are predominantly expressed in BLA neurons but not in astrocytes. beta 1-AR is distributed in the cell membrane and cytoplasm of neurons, whereas beta 2-AR is localized not only in the cell membrane and cytoplasm but also in the nucleus. Intra-BLA infusion of the beta 1-AR antagonist metoprolol and atenolol or the beta 2-AR antagonist ICI118551 and butoxamine produces a severe deficit in 24-h auditory fear memory, leaving 1-h memory intact. Western-blot analysis reveals that the protein level of cytoplasmic beta 1-AR significantly increases 2- and 4-h postconditioning, whereas that of cytoplasmic or nuclear beta 2-AR is unchanged. The present results indicate that beta 1- and beta 2-ARs in the BLA have differential subcellular localizations and both are required for the consolidation of auditory fear memory. (C) 2008 Wiley-Liss, Inc.