Abstract: Methamphetamine (Meth) and related amphetamine compounds, which are potent psychostimulants, are among the most commonly used illicit drugs. With > 35 million users worldwide, Meth abuse poses a significant health and economic threat globally. Acute and chronic doses of Meth have been shown to produce long-term damage in many brain regions. However, the mechanisms underlying Meth neurotoxicity are still not known. The current proposal focuses on one important and emerging player called extracellular vesicles (EVs) and their role in chronic Meth abuse. Extracellular vesicles (EVs) have been garnering increasing interest for their role in several neurological disorders and understanding their role in the brain during drug abuse is just beginning to emerge. EVs can release their cargo into target cells and trigger downstream signaling pathways . Our own recent study has revealed that EV associated microRNA (miRNA) cargo can be responsible for neuronal injury. However, EV miRNA cargo and their involvement in Meth associated neurotoxicity is not well understood thus warranting further studies in this direction. We are particularly interested in understanding the effect of such EV-carried miRNAs on neurons. The overarching goal of this proposal is to examine the role of EVs in the damaging effects of Meth on the central nervous system, specifically in a setting of chronic Meth exposure. During course of this study, we will investigate several key questions in the field including molecular and functional changes in neurons that are specifically driven by EVs during Meth abuse. These studies will be conducted in three specific aims; (1) In Specific aim 1 we will utilize a robust strategy to isolate EVs from archived monkey brain brains and from primary glial cells infected exposed to Meth, characterize them, and determine Meth induced alterations in EV associated miRNA cargo. (2) Specific aim 2 is specifically designed to study synaptodendritic injury and causative mechanism resulting from treatment with EVs isolated from brains and primary glial cells from Meth treated groups and finally in (3) Specific aim 3, we will use a chronic self-administration rat model to study the effects of brain EVs on neuronal damage and determine the importance of sex as a variable. The experiments proposed in this study will unravel crucial signaling events that mediate such neurotoxicity therefore providing a strong foundation to build further therapeutic studies for the eventual prevention of long-term neuronal damage in Meth abuse that considers the role of sex.