Central clock drives foraging rhythm through modulating food odor attraction in Drosophila.

Animals display rhythmic foraging behavior synchronized with the Earth's 24-h cycle. However, the underlying neural mechanism remains poorly understood. In this study, we found that one group of olfactory inhibitory projection neurons (iPNs) in Drosophila, called mlPN3, exhibits circadian responses to food odor and plays an essential role in promoting rhythmic foraging. We show that this circadian activity of mlPN3 neurons is driven by a rhythmic inhibition from a group of dopaminergic neurons (DANs), PAM-β'2. Furthermore, PAM-β'2 DANs are activated in the early morning by a group of circadian neurons, called morning cells, through pigment-dispersing factor (PDF) neuropeptide. Suppressing either PAM-β'2 DANs or morning cells impairs morning foraging, which is fully rescued by inhibiting mlPN3 neurons. Together, our findings show that the constant inhibition on foraging behavior of these iPNs is lifted by the circadian signal through dopaminergic suppression, providing critical insights into the function of the disinhibition circuit in circadian regulation.