Behavioral sensitization is proposed as a process that occurs with repeated administration of drugs of abuse whereby both behavioral and neurochemical responses to the drugs are progressively enhanced. Sensitization has been suggested to be the result of neuroadaptations that also contribute to such phenomenon as drug craving and relapse. These lasting activity-dependent changes require new protein synthesis and remodeling at the synapses. It is well established that mRNA can be transported to neuronal distal processes, where it undergoes localized translation regulated in a spatially restricted manner in response to stimulation. Therefore it is hypothesized that behavioral sensitization in response to intermittent ethanol exposure may result, at least in part, from alterations in the synaptic transcriptome, contributing to synaptic remodeling and plasticity. This hypothesis will be explored through the following specific aims: 1) perform gene expression profiling of the synaptic transcriptome of DBA/2J mice subjected to behavioral sensitization by intermittent repeated ethanol and 2) determine if alterations in the transport of a known ethanol-responsive gene, brain-derived neurotrophic factor (BDNF), modulates ethanol behaviors. Expression profiling of the synaptic transcriptome will be undertaken by isolating RNA from synaptoneurosomes, which are membranous structures formed from the resealing of presynaptic nerve terminals attached to resealed post-synaptic entities obtained through a subcellular fractionation procedure. Bioinformatics analysis of the resulting microarray data will be used to generate gene networks and pathways regulated by repeated ethanol and can be used to prioritize candidate genes for further investigation. Quantitative real time polymerase chain reaction (Q-rtPCR) performed on RNA isolated from synaptoneurosomes from a separate cohort of sensitized animals will be used for independent verification of gene expression changes from the microarray data. Western blot analysis followed by densitometry will be used to quantitate the changes in synaptic proteins encoded by targeted transcripts. Finally, BDNFflox/flox mice, which have reduced levels of synaptic BDNF transcript as a result of a truncated long 3'UTR, will be used to probe the involvement of a synaptically targeted transcript in ethanol-induced behaviors.
Alcoholism is a disease defined by uncontrolled, compulsive, dependent use of alcohol that persists despite adverse consequences that may afflict the user's health, relationships, or occupation. It is estimated to affect 17.6 million people in the United States alone (NIAAA). Despite decades of research and the use of current pharmacological and psychological interventions, the relapse rate for alcoholics remains alarmingly high. Elucidating the molecular mechanisms that underlie the transition to compulsive, uncontrolled alcohol consumption will provide novel targets for the treatment of this disease.