Much attention has been given to the neurochemical and synaptic changes that influence the behavioral effects of alcohol, with emphasis placed on neuronal mechanisms of action. The potential role of astrocytes as targets or mediators of the central effects of alcohol is largely unknown, and is the major focus of this proposal. The rationale behind the proposed studies is in part based on two key findings from the literature: that acute alcohol exposure causes increased extracellular adenosine via blockade of the equilibrative nucleoside transporter 1, and that sensitivity to and consumption of alcohol can be mediated by activation of the src family kinases (SFK) and a known substrate, the NR2B subunit of the NMDAR. Using an astrocyte-specific transgenic mouse, called dnSNARE, we have shown that an astrocytic source of adenosine acting on A1 receptors (A1R) influences NMDAR-mediated synaptic activity and membrane expression of NR2B. In preliminary studies, dnSNARE mice exhibited increased sensitivity to the acute effects of alcohol and decreased alcohol consumption, supporting the involvement of astrocytes in alcohol behaviors. Collectively, this evidence led to the hypothesis that an astrocytic source of adenosine acting on A1Rs contributes to the synaptic and behavioral changes occurring in response to alcohol exposure. The proposed experiments are designed to establish the potential link between astrocytes and the effects of alcohol on A1R activation and NMDAR-mediated synaptic activity. In the first aim, dnSNARE mice will be tested to determine sensitivity to the hypnotic and motor impairing effects of alcohol, and for consumption of and preference for alcohol.
The second aim will employ pharmacology in dnSNARE and control mice to examine whether these characteristic alcohol behaviors involve A1R activation, independently and/or in concert with downstream changes in activation of SFK and the NR2B subunit of the NMDAR. In the third aim, electrophysiology will be used to compare the effects of alcohol on synaptic transmission in brain slices from dnSNARE and control mice, and to test whether astrocyte-regulated activation of A1Rs, SFK, and NR2B mediates alcohol-induced changes in synaptic transmission. By identifying a novel astrocytic target of alcohol, results from these studies have a unique potential to impact the development of therapies for treatment of alcohol abuse and dependence.
It is well known that alcohol affects brain function by altering neurochemicals that are critical for neuronal activity. A population of non-neuronal cells, called astrocytes, are in direct communication with neurons, but the effects of alcohol on these cells is largely unknown. Understanding the potential mechanisms by which alcohol alters signaling between astrocytes and neurons may provide insight into novel therapies for treatment of alcohol dependence.
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