Large Ventral Lateral Neurons Modulate Arousal and Sleep in Drosophila

BACKGROUND Large ventral lateral clock neurons (lLNvs) exhibit higher daytime-light-driven spontaneous action-potential firing rates in Drosophila, coinciding with wakefulness and locomotor-activity behavior. To determine whether the lLNvs are involved in arousal and sleep/wake behavior, we examined the effects of altered electrical excitation of the LNvs. RESULTS LNv-hyperexcited flies reverse the normal day-night firing pattern, showing higher lLNv firing rates at night and pigment-dispersing-factor-mediated enhancement of nocturnal locomotor-activity behavior and reduced quantity and quality of sleep. lLNv hyperexcitation impairs sensory arousal, as shown by physiological and behavioral assays. lLNv-hyperexcited flies lacking sLNvs exhibit robust hyperexcitation-induced increases in nocturnal behavior, suggesting that the sLNvs are not essential for mediation of arousal. CONCLUSIONS Light-activated lLNvs modulate behavioral arousal and sleep in Drosophila.