Mechanosensory Stimulation via Nanchung Expressing Neurons Can Induce Daytime Sleep in Drosophila

The neuronal and genetic bases of sleep, a phenomenon considered crucial for well-being of organisms, has been under investigation using the model organism Drosophila melanogaster. Although sleep is a state where sensory threshold for arousal is greater, it is known that certain kinds of repetitive sensory stimuli, such as rocking, can indeed promote sleep in humans. Here we report that orbital motion-aided mechanosensory stimulation promotes sleep of male and female Drosophila, independent of the circadian clock, but controlled by the homeostatic system. Mechanosensory receptor nanchung (Nan) -expressing neurons in the chordotonal organs mediate this sleep induction: flies in which these neurons are either silenced or ablated display significantly reduced sleep induction on mechanosensory stimulation. Transient activation of the Nan -expressing neurons also enhances sleep levels, confirming the role of these neurons in sleep induction. We also reveal that certain regions of the antennal mechanosensory and motor center in the brain are involved in conveying information from the mechanosensory structures to the sleep centers. Thus, we show, for the first time, that a circadian clock-independent pathway originating from peripherally distributed mechanosensors can promote daytime sleep of flies Drosophila melanogaster.