| Goals of Dissertation Research. Cocaine use and abuse is a burden on society with high treatment costs and high relapse rates despite rehabilitation efforts. Many studies have tried to identify changes in gene expression that are associated cocaine abuse (Chapter 1A); however, the goal of this dissertation research was to identify molecules that may play a role not only in cocaine abuse, but also in relapse-associated behaviors. The central hypothesis of this research was that increases in drug-seeking and drug-taking behavior, which occur during periods of abstinence from cocaine self-administration, produce (or are caused by) differential regulation of the proteomic and gene expression profiles in brain regions associated with drug abuse. Identification of these changes may help to elucidate the molecular mechanisms of abstinence-induced behaviors and provide targets for therapeutic intervention.;Specific Aims. Specific Aim 1: Testing the hypothesis that enforced abstinence from cocaine self-administration is accompanied by protein expression changes in the mesolimbic system (Chapter 2). A large-scale discovery experiment was conducted using 2-dimensional differential in-gel electrophoresis (2D-DIGE), to elucidate protein expression changes that occur during abstinence from cocaine self-administration in the medial prefrontal cortex.;Specific Aim 2: Modify existing methods to isolate high-quality synaptosomes from brain tissue and examine the idea that changes occur in the expression of proteins associated with exocytosis and endocytosis at the synapse during periods of abstinence from cocaine self-administration (Chapter 3). A directed study of protein expression was conducted on isolated synaptosomes to directly look at the effect of enforced abstinence on this sub-cellular compartment.;Specific Aim 3: Testing the hypothesis that enforced abstinence from cocaine self-administration is accompanied by gene expression changes in the mesolimbic system (Chapter 4). A whole-genome microarray analysis of the medial prefrontal cortex and nucleus accumbens was conducted to identify changes in mRNA expression that result from cocaine self-administration followed by increasing periods of abstinence.;Original Breakthroughs and Findings. Identified in these studies was a panel of changes that occur following cocaine self-administration and increasing periods of enforced abstinence. Using a systems biology approach, the combined analysis of these changes reveals possible mechanisms by which relapse-associated behaviors incubate over periods of abstinence from cocaine. Such mechanisms include changes in neuronal structure and synaptic plasticity, signal transduction (specifically MAPK, TNF, and calcium signaling), and changes in glial cell function. Additionally, preliminary epigenetic analysis of identified changes in mRNA expression (Appendix) illuminates a possible mechanism by which persistent changes in gene and protein expression may occur. Together, these data open the door for future examination of the functional effect of these changes, as well as providing possible targets for therapeutic intervention. |
