Mariam Vázquez^{1, 3} and Bruno Marie^{1, 2, 3}

¹   Institute of Neurobiology, University of Puerto Rico, Medical Sciences Campus, San

Juan, Puerto Rico.

²   Department of Anatomy and Neurobiology, University of Puerto Rico, Medical

Sciences Campus, San Juan, Puerto Rico.

³   Molecular Sciences Research Center, University of Puerto Rico, Puerto Rico

bruno.marie@upr.edu

Introduction: Alcoholism is an ubiquitous and increasing problem in society. Alcohol provokes changes in the nervous system that underlie changes in behavior and lead to addiction. Understanding the consequences of acute exposure to chronic consumption of alcohol on the nervous system will enable us to decipher the mechanisms leading to addiction. Studies about the effects of alcohol on the nervous system have been prolific, especially alcohol’s postsynaptic targets and mechanisms. Meanwhile, the effects on presynaptic proteins have been less studied.

Methods: We aimed to identify changes in synaptic morphology and presynaptic protein expression at the Drosophila NMJ after acute and chronic exposure to alcohol. Using immunohistochemistry and confocal and super-resolution microscopy, we characterized the synapse by quantifying synaptic boutons and active zones. We also measured the presence and quantity of essential presynaptic proteins (Syntaxin 1A, Synaptotagmin 1, Synapsin) that are possible molecular targets of alcohol.

Results: Acute exposure to alcohol did not affect the synapse nor protein expression. In contrast, chronic treatment impacted synaptic growth and composition. We found that there was a 30% decrease in number of boutons and a 24% decrease in active zones, showing that chronic alcohol exposure can dramatically impact synapse development. In addition, we assessed vesicle proteins and found that Syntaxin 1a increased by 20% and Synaptotagmin 1 increased by 26% after chronic exposure to alcohol. In contrast, this treatment did not affect Synapsin expression, showing that chronic alcohol only provokes the change of a subset of synaptic proteins.

Conclusion: Although acute exposure to alcohol does not affect the structure of the Drosophila NMJ, chronic alcohol exposure impacts synaptic growth and presynaptic protein expression. Elucidating how alcohol targets the synapse and presynaptic proteins may provide a mechanism that explains the changes in behavior that may lead to addiction after alcohol exposure.

Acknowledgements: This work was supported by the NIH NINDS-R21NS114774 to BM, the NSF HRD-1736019 grants to MV and BM. Confocal and super resolution microscopy was supported by NIH NIGMS COBRE P20GM103642.