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Transporter Mechanism of Amphetamine Sensitization

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This proposal will provide for the first time characterization and understanding of amphetamine (AMPH)- induced dopamine transporter (DAT) and serotonin transporter (SERT) trafficking in the AMPH sensitized mouse. Repeated AMPH in humans and laboratory animals leads to a behavioral and neurochemical sensitization which may underlie the incentive salience of drugs, e.g., "drug wanting". Understanding the effect of drugs on a sensitized animal is of significant clinical relevance given that human drug addicts, often already sensitized to drugs, repeatedly take drugs. Since AMPH exerts its effect by binding to surface DAT, DAT trafficking is important for the strength and duration of DAT substrate (AMPH and dopamine) action. DAT trafficking is primarily induced by DAT substrate (e.g. AMPH) and D2R agonist (e.g. quinpirole). AMPH is also a substrate for SERT, and SERT is importantly involved in AMPH reinforcement and sensitization. SERT trafficking is regulated by substrates. An alteration in repeated AMPH-induced DAT and SERT trafficking will affect dopaminergic and serotonergic signaling, which may contribute to the cellular mechanisms of AMPH sensitization or tolerance upon repeated AMPH exposure. This proposal will expand upon my present non-NIH funded grant to analyze three specific aims: 1) characterize AMPH- and quinpirole-induced DAT internalization and recycling in AMPH sensitized vs. saline- treated mice and determine whether PKC2 plays a role;2) determine if repeated AMPH will alter SERT trafficking and enhance serotonin efflux, and whether or not PKC2 plays a role;and 3) determine if repeated AMPH alters syntaxin 1A association with DAT and SERT. This will be the first study to investigate DAT and SERT trafficking in AMPH sensitized state in rodents, and may shed light on different phases of drug responses in humans upon drug exposure and during withdrawal. This study has a broad application because DAT and/or SERT are implicated in many other neuropsychiatric diseases such as schizophrenia, bipolar disorder and depression, which are commonly comorbid with drug abuse. 1

PUBLIC HEALTH RELEVANCE: Human drug craving and abuse is modeled by amphetamine sensitization in rodents induced by repeated amphetamine treatment. Understanding the trafficking of dopamine transporter and serotonin transporter in the animal model of amphetamine sensitization will provide pertinent information about the dopaminergic and serotonergic signaling in the state of drug sensitization in drug addicts, and provide a new cellular avenue for potential drug intervention. The changes found in dopamine and serotonin trafficking will also be relevant to schizophrenia bipolar disorder and depression, which are often comorbid with substance abuse.

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