Clock neurons on the side of fruit flies produce three signaling chemicals and connect with multiple parts of the daily rhythm network and other systems

The three lateral posterior neurons (LPNs) in Drosophila exhibit distinct morphologies and synaptic connections that may influence sleep and activity patterns.

• Two of the LPNs likely promote sleep, while one unique LPN may promote wakefulness.
• The LPNs form numerous connections with other circadian clock neurons that regulate daily activity.
• All three LPNs rhythmically express neuropeptides, with peak levels occurring in the morning and evening.
• These neuropeptides may interact with the insect hormonal center, potentially affecting metabolism, feeding, and reproduction.
• LPNs are heterogeneous in structure and function, contributing to a complex neural network regulating circadian rhythms.

Simplified