Cocaine is a reinforcing drug with high abuse liability and substantial morbidity and mortality. Cocaine's potent actions on dopamine (DA), serotonin (5-HT) and norepinephrine (NE) transport are well known. However, the relationship between the long-term effects of chronic cocaine abuse and the regional neuroadaptive changes in human brain is less certain. Because the transit of cocaine from the Caribbean corridor to the United States frequently occurs through South Florida, Metropolitan Miami-Dade County has continued to have a high incidence of cocaine-related deaths. In collaboration with the Miami-Dade County Medical Examiner Department, we have developed a bank of postmortem brain specimens from cocaine users. Based on a retrospective case control analysis of the toxicology reports, scene descriptions, supplemental background information, interviews with next-of-kin, and autopsy findings, we assign cases into three groups: cocaine-related sudden death, excited cocaine delirium, and drug-free control subjects. The proposed studies are designed to identify neuroadaptive and neurodegenerative changes in biogenic amine pathways in the postmortem human brain. Neuroadaptation and neurodegeneration in DA, 5-HT and NE systems are central to the vulnerability, progression and long-term consequences of addictive behavior. DAergic signaling underlies the reinforcing properties of cocaine, while serotonergic dysfunction may be associated with behavioral disinhibition and negative mood states. Recent studies of the noradrenergic system suggest that a dysregulation of NE transport by cocaine may contribute to cerebrogenic cardiovascular and autonomic disturbances that lead to sudden death. Specifically, we plan to test the following hypotheses: 1.) DA transporter upregulation occurs in parallel with an increase in the expression of alpha-synuclein protein in DA and NE neurons. 2.) Asymmetric changes in NE transporter expression occurs in higher brain autonomic centers (insula and amygdaloid subnuclei) in cocaine-related sudden death as compared to age-matched drug-free control subjects. This neuroadaptive change in NET will be a specific marker of cocaine toxicity. 3.) Regulatory changes in biogenic amine transporters and kappa opioid receptor numbers will show lateral asymmetry in the amygdala and anterior insular cortex. 4.) Changes in particular biogenic amine transporters and gene transcripts are specific to the pathology of cocaine excited delirium. The power of the proposed study derives from an integration of molecular and anatomical approaches in examining postmortem human brain from chronic cocaine users. Together, these studies will provide a molecular and circuit-based accounting of the abnormalities in biogenic amine systems in cocaine toxicity.
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