The Deleterious Influence of Adolescent Alcohol Misuse on the Structural Cohesion of the Tripartite Synapse

Adolescent binge drinking impairs cognitive function in both human and animal models and increases the risk of developing an alcohol use disorder. Recent research indicates that adolescent intermittent ethanol (AIE) exposure, a rat model of binge drinking, disrupts the tripartite synapse. This is composed of a pre- and post-synaptic terminal and an ensheathing peripheral astrocyte process (PAP) that is critical in regulating synaptic function. Tripartite synapses are stabilized by several bridging proteins, e.g., neuroligin and neurexin, that are essential for maintaining synaptic health. Previously, our laboratory has shown that AIE results in a progressive loss of PAP-synaptic coupling at excitatory synapses in the hippocampus. We hypothesize that AIE disrupts the interaction between neurexin-neuroligin, driving a loss of tripartite synapse structural integrity, and subsequent PAP-synaptic decoupling. To conduct this research, Sprague Dawley rats were subjected to AIE or water intermittently over 16 days. After various washout/abstinence periods, brain samples were collected for analysis using techniques such as adeno-associated virus (AAV) to assess astrocyte morphology and immunohistochemistry, western blotting, and co-immunoprecipitation to assess changes in bridge protein expression and interactions. The primary focus was on samples collected at 26 days of washout, as previous studies have shown the most significant uncoupling at this stage. We will show how AIE disrupts PAP-synaptic coupling and how alterations in neurexin and neuroligin interactions contribute to this decoupling. Whether changes in astrocyte morphology contribute to the loss of physical interactions at the synapse remains to be determined and will be the focus of our future investigations.