Through the proposed research and training I will improve my research skills and continue to investigate neural substrates underlying the complex phenomenon of memory. Specifically, the long-term goal of this project is to understand the contribution of ubiquitin-proteasome mediated protein degradation to the stability of long-term memory in the amygdala following retrieval. The contribution of this molecular process will be examined using two approaches. The first approach is to quantify the rate of protein degradation following memory retrieval using a highly selective GST-protein fusion system, which is an in vitro protein purification technique, and highly specific tissue fractionation procedure, which provides a synaptosomal membrane fraction. The second approach is to manipulate specific molecular processes in the amygdala with infusions of drugs that prevent protein degradation through the ubiquitin-proteasome system, protein synthesis by blocking translation, glutaminergic activity by blocking NMDA receptors, and intracellular signaling by blocking several protein kinases. Four specific aims will be addressed. The first aim is to determine whether protein degradation is increased in the amygdala following the retrieval of context and auditory fear memories. To achieve this aim, fear conditioning will be used to create aversive context- and auditory-based memories and the rate of protein degradation will be quantified in the amygdala following retrieval using the GST-protein fusion system. The second aim, which addresses what the specific synaptic targets of the ubiquitin- proteasome system are following retrieval, will be achieved using the synaptosomal membrane preparation and GST-protein fusion system. The third aim, which addresses whether protein degradation in the amygdala is critical for the reconsolidation of context and auditory fear memories, will be achieved using targeted infusions of drugs that block protein degradation and protein synthesis. The final aim is to determine what molecular mechanisms signal these increases in protein degradation within the amygdala following retrieval. To achieve this aim, infusions of drugs which block NMDA receptor activity and several intracellular signaling cascades will be given prior to retrieval and the rate of protein degradation will be quantified following retrieval using the GST-protein fusion system. Collectively, this set of experiments will answer questions about whether proteasome-dependent protein degradation 1) is involved in postsynaptic density rearrangement following retrieval, 2) is critically involved in amygdala-dependent fear memory reconsolidation, 3) is underlying the requirement for protein synthesis in the reconsolidation process and 4) is being triggered by the same mechanisms which regulate protein synthesis and the "destabilization" of stored memory following retrieval.