Updated project metadata. The postsynaptic density (PSD) of excitatory synapses contains a highly organized protein network with thousands of proteins and is key node in the regulation of synaptic plasticity. To gain new mechanistic insight into experience-induced changes in the PSD, we examined the global dynamics of the hippocampal PSD proteome and phosphoproteome in mice following 4 different types of experience. Mice were trained using an inhibitory avoidance (IA) task and hippocampal PSD fractions were isolated from individual mice to investigate molecular mechanisms underlying experience-dependent remodeling of synapses. We developed a new strategy to identify and quantify the relatively low level of site-specific phosphorylation of PSD proteome from the hippocampus, by using a modified iTRAQ-based TiSH protocol. In the PSD, we identified 3,938 proteins and 2,761 phosphoproteins in the sequential strategy covering a total of 4,968 unique protein groups (at least 2 peptides including an unique peptide). On the phosphoproteins, we identified a total of 6,188 unambiguous phosphosites (75% site localization probability)