These studies propose to investigate the long-term consequences of cocaine and opiate administration on molecular indices of dopaminergic function. A central problem in substance abuse research is identifying how chronic drug administration changes the brain so as to account for the long-term problems of physical dependence, psychological addiction, and tolerance. One hypothesis is that the drugs create an epigenetic imprint. That is, the chronic administration of drug alters the pattern of gene expression- the levels of RNA and protein- such that they change the state of the brain. The experiments proposed in this portion of the center application are designed to address this issue in a multi-disciplinary way by focusing on a recognized neuroanatomical substrate of substance abuse- the mesolimbic dopamine pathway. Utilizing recombinant DNA research tools developed during the last funding cycle, in combination with the facilities and expertise of both primate and rodent investigators within the Center, the following specific aims will be undertaken. In SA #1, we will test the hypothesis that chronic cocaine regulates dopaminergic gene expression in the non-human primate. Pursuing previous studies from this laboratory and others within the Center, SA #2 will examine the long-term epigenetic consequences of administration of tropane analogs with markedly different pharmacokinetics and transporter selectivity than cocaine. Further experiments are planned to identify molecular correlates for physiological and neurochemical disparities observed based on the context of drug administration. Accordingly, SA #3 will establish the relationships between epigenetic imprinting by response-dependent (self- administration) versus response-independent cocaine administration in the rodent. Finally, SA #4 will examine the hypothesis that opiate administration can alter molecular indices f dopaminergic function. These studies will continue the progress we have made in understanding how long- term drug administration affects neuronal set-points and how this might account for long-term drug abuse liabilities.
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