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Abstract
P2X receptors (P2XRs) are a family of cation-permeable, ligand-gated ion channels gated by synaptically released extracellular adenosine-5'-triphosphate (ATP). Of the seven P2XR subtypes (P2X1-P2X7), P2X4 is the most abundantly expressed subtype in the central nervous system and to date is the most ethanol sensitive when measured in recombinant expression systems. Previous work demonstrates that ethanol inhibits ATP-activated currents in rat and mouse neurons, suggesting a role for P2X4Rs in ethanol-related behaviors. A recent in vivo study identified p2rx4 as a candidate gene linked to ethanol intake and/or preference in rodents. Despite these reports, the lack of specific agonists and antagonists has hampered our ability to directly determine the role that P2X4Rs play in regulating ethanol-induced behaviors. The availability of p2rx4 null (i.e., knockout; KO) mice has partially overcome this limitation. However, transgenic animal models do not allow for brain-regional analysis of P2X4R regulation on ethanol drinking and the effect of constitutive p2rx4 gene deletion on general behavior has not been assessed. This dissertation addresses these issues via a two-pronged approach utilizing transgenic mice and lentiviral gene delivery techniques to investigate the hypothesis that P2X4Rs play a role in regulating ethanol intake. Chapter 2 involves characterization of inherent behaviors in P2X4R KO mice, specifically meant to capture changes in general behavior and emotional reactivity. Chapter 3 examines differences between wildtype C57Bl/6 and KO mice in ethanol intake and begins to elucidate the role of P2X4Rs in the underlying mechanisms for differential drinking. Finally, Chapter 4 describes the development of lentiviral vectors for spatial and temporal control of P2X4R expression and begins to investigate the regulation of ethanol intake by P2X4Rs in the striatum (i.e., nucleus accumbens; NAc). Findings from each experimental chapter support the notion that a deficiency in P2X4Rs 1) causes perceptual and socio-communicative functions akin to autism spectrum disorder; 2) increases ethanol intake in two drinking paradigms that model different degrees of alcohol consumption and 3) suggests a specific role for accumbal P2X4Rs in regulating ethanol intake in mice. Overall, these studies increase our knowledge regarding the broad spectrum of P2X4R involvement in alcohol and non-alcohol behaviors and implicate P2X4Rs as a molecular target for novel therapies to treat alcoholism and select endophenotypes related to neurodevelopmental disorders.