TY - JOUR T1 - Ethanol Regulates Presynaptic Activity and Sedation through Presynaptic Unc13 Proteins in Drosophila JF - eneuro JO - eNeuro DO - 10.1523/ENEURO.0125-18.2018 SP - ENEURO.0125-18.2018 AU - Shiyu Xu AU - Satyabrata Pany AU - Kevin Benny AU - Khadeeja Tarique AU - Ola al-Hatem AU - Kathleen Gajewski AU - J. Leigh Leasure AU - Joydip Das AU - Gregg Roman Y1 - 2018/06/04 UR - http://www.eneuro.org/content/early/2018/06/04/ENEURO.0125-18.2018.abstract N2 - Ethanol has robust effects on presynaptic activity in many neurons, however, it isn't yet clear how this drug acts within this compartment to change neural activity, nor the significance of this change on behavior and physiology in vivo. One possible presynaptic effector for ethanol is the Munc13-1 protein. Herein, we show that ethanol binding to the rat Munc13-1 C1 domain, at concentrations consistent with binge exposure, reduces diacylglycerol binding. The inhibition of diacylglycerol binding is predicted to reduce the activity of Munc13-1 and presynaptic release. In Drosophila, we show that sedating concentrations of ethanol significantly reduce synaptic vesicle release in olfactory sensory neurons, while having no significant impact on membrane depolarization and Ca2+ influx into the presynaptic compartment. These data indicate that ethanol targets the active zone in reducing synaptic vesicle exocytosis. Drosophila, haploinsufficent for the Munc13-1 ortholog Dunc13, are more resistant to the effect of ethanol on presynaptic inhibition. Genetically reducing the activity of Dunc13 through mutation or expression of RNAi transgenes also leads to a significant resistance to the sedative effects of ethanol. The neuronal expression of Munc13-1 in heterozygotes for a Dunc13 loss-of-function mutation can largely rescue the ethanol sedation resistance phenotype, indicating a conservation of function between Munc13-1 and Dunc13 in ethanol sedation. Hence, reducing Dunc13 activity leads to naïve physiological and behavioral resistance to sedating concentrations of ethanol. We propose that reducing Dunc13 activity, genetically or pharmacologically by ethanol binding to the C1 domain of Munc13-1/Dunc13, promotes a homeostatic response that leads to ethanol tolerance.Significance Statement At relatively low concentrations, ethanol inhibits the activity of many presynaptic termini (Liu and Hunt, 1999). Homeostatic changes in presynaptic activity are proposed to underlie the formation of functional tolerance (Koob and Bloom, 1988; Ghezzi and Atkinson, 2011). We do not currently know where ethanol binds to bring about changes in presynaptic activity and homeostasis. We now show that ethanol will bind to the C1 domain of the Munc13-1 protein at intoxicating concentrations and inhibit the binding of diacylglycerol. Reducing the activity of the Drosophila Dunc13 ortholog leads to a homeostatic change that promotes behavioral and physiologic resistance to intoxicating levels of ethanol. Hence, Unc13 proteins are likely sites for ethanol’s action within the presynaptic compartment that bring about tolerance. ER -