The goal of the study is to link brain-derived neurotrophic factor (BDNF) to alcohol-drinking behavior. It is hypothesized that decreased BDNF in the mesolimbic dopamine (DA) pathway, a brain circuit that has been implicated in alcohol's rewarding effects, is associated with high alcohol intakes. This hypothesis is prompted by our finding showing innate deficiencies of BDNF in the nucleus accumbens (NACC) of alcohol-preferring (P) rats compared with alcohol-nonpreferring (NP) rats. Previous studies performed in heterozygous BDNF (+/-) mice have shown the relationship between BDNF and alcohol consumption, but they cannot identify brain area(s) in which BDNF may play a role in regulating alcohol intakes. In addition, the approach of genetically modifying animals for target validation is often limited by developmental adaptation and genetic compensation that may mask the establishment of a clear phenotype. Recently, RNA interference (RNAi) has become a valuable tool for investigating gene function. The applicant has generated a lentiviral vector that is capable of delivering and expressing short hairpin RNA that targets BDNF mRNA. This vector has been proved to be effective in silencing the BDNF gene both in vitro and in vivo in our preliminary study. To determine whether RNAi-mediated inhibitions of BDNF expression in the VTA and/or NACC increase alcohol intakes, this lentivirus and several control substances will be bilaterally infused into the VTA or the NACC of groups of the Wistar rat, the progenitor from which the P/NP rats were originally derived. Then, the effects of the infusion on alcohol consumptions and non-alcohol tastant preference are determined by a two-bottle free-choice method and compared among different treatment groups. BDNF expression at the protein level in each brain area after the treatments is also assessed via the enzyme-linked immunosorbent assay and immunohistochemistry to see whether reductions of BDNF expression are associated with increased alcohol intakes. This study would provide more direct evidence for the role of BDNF in alcohol intakes and specifically addresses whether reductions of BDNF in the mesolimbic DA pathway are associated with increased alcohol consumptions. Since there are no reports regarding silencing the BDNF gene in vivo to date, the establishment of the approach to inhibit BDNF expression, particularly in the mesolimbic DA system of intact animals, would benefit researchers in drug addiction including alcoholism.
