Circadian Modulation of Alcohol-Induced Sedation and Recovery in Male and Female Drosophila

Abstract

Delineating the factors that affect behavioral and neurological responses to alcohol is critical to facilitate measures for preventing or treating alcohol abuse. The high degree of conserved molecular and physiological processes make Drosophila melanogaster a valuable model for investigating circadian interactions with alcohol-induced behaviors and examining sex-specific differences in alcohol sensitivity. We found that wild-type Drosophila exhibit rhythms in alcohol-induced sedation under light-dark and constant dark conditions with considerably greater alcohol exposure necessary to induce sedation during the late (subjective) day and peak sensitivity to alcohol occurring during the late (subjective) night. The circadian clock also modulated the recovery from alcohol-induced sedation with flies regaining motor control significantly faster during the late (subjective) day. As predicted, the circadian rhythms in sedation and recovery were absent in flies with a mutation in the circadian gene period or arrhythmic flies housed in constant light conditions. Flies lacking a functional circadian clock were more sensitive to the effects of alcohol with significantly longer recovery times. Similar to other animals and humans, Drosophila exhibit sex-specific differences in alcohol sensitivity. We investigated whether the circadian clock modulated the rhythms in the Loss-of-Righting Reflex, alcohol-induced sedation, and recovery differently in males and females. We found that both sexes demonstrate circadian rhythms in the Loss-of-Righting Reflex and sedation with the differences in alcohol sensitivity between males and females most pronounced during the late subjective day. Recovery of motor reflexes following alcohol sedation also exhibited circadian modulation in male and female flies, although the circadian clock did not modulate the difference in recovery times between the sexes. These studies provide a framework outlining how the circadian clock modulates alcohol-induced behaviors in Drosophila and identifies sexual dimorphisms in the circadian modulation of alcohol behaviors.

Aging and circadian dysfunction increase alcohol sensitivity and exacerbate mortality in Drosophila melanogaster

“…Stereotypical alcohol behaviors are highly conserved across species (Guarnieri and Heberlein, 2003, Rodan and Rothenfluh, 2010, Wolf et al, 2002). Moreover, Drosophila exhibit circadian rhythms in alcohol-induced loss of motor control, sedation, and recovery following a single binge-like alcohol exposure (De Nobrega and Lyons, 2016, van der Linde and Lyons, 2011) comparable to the circadian regulation of alcohol-induced behaviors observed in mammalian models.…”

“…1C and D). To determine whether phase specific differences occurred in alcohol responses between 3 d and 10 d flies, we analyzed the magnitude of the difference in the 50% LoRR between age groups at each time point as previously done (De Nobrega and Lyons 2016). The largest factor contributing to the decreased amplitude of the rhythm appeared to be a phase specific increase in alcohol sensitivity during the late subjective day (ANOVA: F 5, 102 = 7.92, p < 0.001).…”

“…To control for stress induced by culture conditions, flies were collected following eclosion and distributed with approximately 25 – 30 flies per vial and subsequently transferred every 3-4 days to new vials. For experiments in which constant light (LL) was used to induce arrhythmicity, CS flies were collected on the day of eclosion and subsequently maintained in constant light (25 °C; 60-70% humidity) as previously (De Nobrega and Lyons, 2016, Lyons and Roman, 2009). Zeitgeber time (ZT) represents time under light-dark entrainment conditions with ZT 0 denoting lights on (dawn) and ZT 12 signifying lights off (dusk).…”

“…Alcohol delivery occurred using an alcohol vapor system in the dark as previously described (De Nobrega and Lyons, 2016, van der Linde et al, 2014, van der Linde and Lyons, 2011). Briefly, four tubes of flies (approximately 30 flies per tube) were exposed to a mixture of alcohol vapor and humidified air at a predetermined ratio of 95% alcohol and de-ionized water (Koptec, Declon Labs, Inc. King of Prussia, PA).…”

“…Sedation was performed as previously (De Nobrega and Lyons, 2016, van der Linde et al, 2014). Flies were exposed to 40% alcohol vapor on the second day of DD, except for 3 d flies that were exposed to 50% alcohol vapor to avoid tolerance development within the time period to sedation.…”