Protein-protein interaction is a widely existing phenomenon and is essential for almost all biological processes, extending from the formation of cellular macromolecular structures and enzymatic complexes to the regulation of signal transduction pathways. Proteins interact with each other through the dynamic associations between modular protein domains within different cellular compartments and with distinct temporal dynamics. Disrupting protein interactions has emerged as an effective way to specifically modulate certain signaling pathways. Tat-tagged peptide mimics are a recently developed experimental tool that is used to disrupt specific interactions between protein complexes. TAT, an 11-amino acid protein transduction domain from HIV Tat protein, is tagged to peptides that mimic the functional fragment of protein interaction domains, and facilitates the delivery of peptides into cells to disrupt the associated protein both competitively and selectively. Here we provide a technical description on the utilization of Tat-tagged peptide mimics as a tool to disrupt protein interaction in cultured neurons and in the rat brain.