Abstract
Sleep and metabolism are closely related and nutritional elements such as sugars and amino acids are known to regulate sleep differently. Here we comprehensively investigated the effects of D-amino acids fed in the diet on the sleep of Drosophila melanogaster. Among 19 amino acids examined, both D-serine (Ser) and D-glutamine (Gln) induced a significant increase in sleep amount and the effect of D-Ser was the largest at the same concentration of 1% of the food. The effects were proportional to its concentration and significant above 0.5% (about 50 mM). D-Ser is known to bind NR1 subunit of NMDA type glutamate receptor (NMDAR) and activate it. D-Ser did not increase the sleep of the NR1 hypomorphic mutant flies indicating its effects on sleep is mediated by NMDAR. In addition, hypomorphic mutants of D-amino acid oxidase (Daao1), which catabolizes D-amino acids and its disruption is known to increase D-Ser in the brain, showed increase in sleep. These results altogether suggested that D-Ser activated NMDAR in the brain thus increase sleep, and that D-Ser work physiologically to regulate sleep.
