Researchers at the University of Geneva have mapped a neural circuit in Drosophila melanogaster that connects the biological clock to dopamine-producing neurons, revealing how circadian rhythms regulate daytime wakefulness through the mushroom body.
Neural Mapping of Circadian Rhythms in the Fruit Fly Brain
Sleep and wakefulness are governed by an internal biological system that maintains approximately 24-hour rhythms. While science has long understood that this circadian clock controls cycles of rest, body temperature, and hormone production, the specific neural pathways translating these temporal rhythms into actual behavioral changes remained poorly understood. At the Section of Biology of the UNIGE Faculty of Science, Emi Nagoshi’s laboratory tackled this problem using the fruit fly. By employing genetic mapping of connections between neurons, the team identified the nerve cells located downstream of the biological clock.
Imaging techniques that measure neuronal activity revealed that this activity varies throughout the day. The clock communicates with a population of neurons that produce dopamine, a molecule that enables neurons to communicate with one another.
Dopaminergic Circuits and the Mushroom Body
Dopamine serves as a central role in promoting wakefulness in this circuit. When clock neurons fire, they exert an inhibitory effect on these dopaminergic cells. That suppression lowers the wake-promoting signal across the network.
Blanca Lago Solis and Rafael Koch, postdoctoral researcher and research associate in Emi Nagoshi’s group, mapped this exact dynamic:
Through this relay, the biological clock can transmit information about the time of day to a brain circuit involved in regulating sleep and wakefulness.
Implications for Circadian Disruption
Disruptions of the circadian clock are associated with various sleep disorders and alterations in brain function.
