Peptide signals play a key role in controlling the body's daily rhythms in the brain's clock center

Mice lacking the VPAC2 receptor exhibit altered circadian rhythms and fail to show circadian expression of core clock genes.

• PACAP and VIP are two neuropeptides that play distinct roles in regulating circadian rhythms in mammals.
• Mice deficient in the PACAP-selective PAC1 receptor can maintain robust circadian patterns despite altered light responsiveness.
• VPAC2 receptor null mice rely on light for activity regulation and do not display consistent circadian behaviors in constant darkness.
• These mice show immediate re-entrainment to changes in the light/dark cycle, indicating a disruption in their internal clock.
• Lack of VIP signaling in the SCN correlates with the absence of rhythmic expression of core clock genes and the clock-controlled gene AVP.

Simplified