Extinction of aversive memories has been a major concern in neuropsychiatric disorders such as anxiety disorders and drug addiction. However, the mechanisms underlying extinction of aversive memories are not fully understood. Here, we report that extinction of conditioned place aversion (CPA) to naloxone-precipitated opiate withdrawal in male rats activates Rho GTPase Rac1 in the ventromedial prefrontal cortex (vmPFC) in a BDNF-dependent manner, which determines GABAA receptor (GABAAR) endocytosis via triggering synaptic translocation of activity-regulated cytoskeleton-associated protein (Arc) through facilitating actin polymerization. Active Rac1 is essential and sufficient for GABAAR endocytosis and CPA extinction. Knockdown of Rac1 expression within the vmPFCof rats using Rac1-shRNA suppressed GABAAR endocytosis and CPA extinction; whereas expression of a constitutively active form ofRac1 accelerated GABAAR endocytosis and CPA extinction. The crucial role of GABAAR endocytosis in the LTP induction and CPAextinction is evinced by the findings that blockade of GABAAR endocytosis by a dynamin function-blocking peptide (Myr-P4) abolishes LTP induction and CPA extinction. Thus, the present study provides first evidence that Rac1-dependent GABAAR endocytosis plays an crucial role in extinction of aversive memories and reveals the sequence of molecular events that contribute to learning experience modulation of synaptic GABAAR endocytosis.SIGNIFICANCE STATEMENTThis study reveals that Rac1-dependent GABAARendocytosis plays an crucial role in extinction of aversive memories associated with drug withdrawal and identifies Arc as a downstream effector of Rac1 regulations of synaptic plasticity as well as learning and memory, thereby thereby suggesting therapeutic targets to promote extinction of the unwanted memories.