Timed Activation of Morning and Evening Brain Clocks Shifts the Daily Rhythm in Fruit Flies

The depolarization of all clock neurons in Drosophila melanogaster resulted in a phase response curve (PRC) resembling the light PRC, with significant phase delays and modest advances.

• Phase delays were observed during the first half of the subjective night, while modest phase advances occurred in the second half.
• Activation of pigment-dispersing factor (PDF)-positive morning neurons induced phase advances that extended into the subjective day.
• Evening neurons and PDF-positive l-LNvs appeared to mediate phase delays in the activity rhythm.
• The molecular clock, indicated by Period protein cycling, shifted in parallel with behavioral changes after depolarization.
• cAMP response element binding protein B (CREB) was identified as a potential link between membrane depolarization and the molecular clock.

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