Increased vulnerability to stress during opiate dependence: Molecular, anatomical, and behavioural correlates

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Heroin addiction is a major health and societal problem in Australia. It is consistently associated with an adverse impact upon individual users, their families, and communities. It is a chronically relapsing condition for which few, if any effective prevention and treatment strategies exist. Moreover, why an individual initiates and maintains heroin taking remains unclear. Stress and negative emotions have a strong impact on heroin use. Stress may drive some individuals to start using heroin, stress increases the pleasurable effects of heroin and stress increases the aversive effects of heroin withdrawal. These effects will encourage addiction and discourage addicts from seeking treatment. Stress can also cause an otherwise drug-free individual to relapse to heroin addiction despite having been drug-free for some time. In this project we will study why stress has such a large impact on heroin addicts and heroin addiction. We will test the hypothesis that heroin use actually produces profound alterations in the neural network in the brain which controls responses to stress. This project uses a simple animal model of heroin addiction whereby rats are injected with morphine to study the regulation of several genes which are important in responding to stress. We will also study how this exposure and changes in gene expression alter neurobiological, cardiovascular, and behavioural responses to stress. This project will identify parts of the brain that are altered during heroin addiction, and will also identify why heroin addicts are more vulnerable to stress than the general population. Therefore, this project will help us to identify targets for therapeutic intervention (both psychological and pharmacological) and possibly disrupt the addictive cycle.