Effect of taurine and caffeine on sleep–wake activity in Drosophila melanogaster

Abstract

Caffeine and taurine are two major neuromodulators present in large quantities in many popular energy drinks. We investigated their effects on sleep-wake control in constant darkness using the fruit fly Drosophila as a model system. It has been shown that caffeine, as the most widely used psychostimulant, can boost arousal through the dopamine pathway in the mushroom bodies of flies. Taurine is a GABA receptor agonist, which is inhibitory to neuronal firing. We show here that flies receiving a low dose of caffeine (0.01%) increase locomotor activity by 25%, and decrease total sleep by 15%. Treatment with taurine at 0.1% to 1.5% reduces locomotor activity by 28% to 86%, and shifts it from diurnal to nocturnal. At 0.75%, taurine also increases total sleep by 50%. Our results show that taurine increases sleep, while caffeine, as previously reported, attenuates sleep. Flies treated with both caffeine and taurine exhibit two differential effects which depend upon the ratio of taurine to caffeine. A high taurine:caffeine ratio promotes sleep, while a low ratio of taurine:caffeine inhibits sleep to a greater extent than the equivalent amount of caffeine alone. This intriguing enhancement of caffeine action by low doses of taurine may account for the presence of both compounds in energy-promoting drinks such as Red Bull® and Monster®.

The Taurine Transporter Eaat2 Functions in Ensheathing Glia to Modulate Sleep and Metabolic Rate

“…Eaat2 is a member of the conserved EAAT family of membrane transport proteins [8], raising the possibility that it affects sleep by controlling the movement of ions and neuroactive chemical messengers to and from ensheathing glia. In vitro, Eaat2 is a transporter of taurine [9], which promotes sleep when fed to flies [10]. We find that the acute effect of taurine on sleep is abolished in Eaat2 mutant flies.…”

“…In humans, taurine is one of few serum and urinary metabolites consistently upregulated upon sleep deprivation [35,36], but it remains to be determined whether taurine levels change in the brain under these conditions. Interestingly, flies fed high doses of taurine increase their total sleep by up to 50% [10], although the neurobiological basis for this effect is unknown. To explore whether the ability of Eaat2 to promote daytime wakefulness is related to taurine transport, we tested control flies and Eaat2 n1 mutants for the effects of taurine feeding on sleep.…”

Behavioral Changes and Survival in <i>Drosophila melanogaster</i>: Effects of Ascorbic Acid, Taurine, and Caffeine

“…17) Also, Lin et al reported the interaction of caffeine and/or taurine on locomotion and sleep of Drosophila, and addressed the potential impact of energy drink consumption. 10) Taurine is the second most abundant amino acid in the mammalian brain and is also present in mushroom bodies (MBs) in Drosophila.…”

The Effect of Caffeine Supplementation on Exercise Performance Evaluated by a Novel Animal Model

“…In the literature, the effect of drinks composed by CTG on exercise performance has been compared against placebo [23][24][25][26][27][28] . In humans, improved athletic performance after taking 3-6 mg of caffeine per kg of body weight, has been described in different types of exercise, especially in endurance activities [29][30][31] .…”