Mechanisms of enhanced synaptic drive in basolateral amygdala following stress

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Project Summary Fear conditioning, where an initially neutral warning stimulus becomes associated with an innately aversive stimulus such as nociceptive electric shock, has proven to be an effective model for the study of learning and memory processes generally and how learned experiences contribute to anxiety disorders particularly. We reported that a single experience with a strong stressor leads to a long-term enhancement of fear learning, an effect we termed Stress-Enhanced Fear Learning (SEFL). Previously, we demonstrated the importance of the basolateral amygdala (BLA) in SEFL and that SEFL is accompanied by a long-term upregulation of the GluA1 subunit of the AMPA receptor, specifically in the BLA. AMPA receptors mediate normal excitatory neural transmission. This suggests that SEFL, and perhaps other negative consequences of stress, may be mediated by alterations in excitatory synaptic transmission. However, the precise mechanisms by which stress alters fear conditioning are not known. Such knowledge is important to understand how state variables impact learning and memory processes. Additionally, understanding how stress alters fear learning may point to translational targets for stress-related disorders. Therefore, we propose a series of studies using amygdala slice electrophysiology to address this gap in the literature and open the door to future studies determining the necessary and sufficient mechanisms for SEFL. Our preliminary data using whole-cell recordings indicates that there is enhanced excitatory drive in the basolateral amygdala following SEFL-inducing stress. In this exploratory application we propose to use BLA slice electrophysiology to achieve two aims. First to identify the specific inputs to the BLA that carries this enhanced excitatory drive. The second is to identify the molecular mechanisms responsible for this change in excitatory synaptic transmission focusing on the possibility that an abnormal form of neural plasticity underlies these maladaptive changes.