Loss of VIP-VPAC2 receptor signaling disrupted coordinated day-night variation in SCN neuron excitability, caused neurons to manifest random electrical states, and impaired responses to light-input signals.
Loss of coordinated day-night variationWithout VPAC2 receptors, SCN neurons displayed random electrical states at both day and night instead of the synchronized rhythm seen in normal mice
What the researchers found
VPAC2 receptor knockout mice exhibited loss of coordinated day-night variation in SCN neuronal excitability, with neurons manifesting random electrical states, lacking voltage-gated sodium current components, and showing altered responses to light-pathway input signals.
Why it matters
VIP is one of the most important neuropeptides in circadian biology. Understanding how it coordinates clock neuron activity could lead to treatments for circadian rhythm disorders, jet lag, shift work problems, and the many diseases linked to disrupted body clocks (metabolic syndrome, depression, cancer risk).
The numbers in context
Recordings captured day-night variation in neuronal excitability across the circadian cycle in both knockout and wild-type mice.
How the study worked
Patch-clamp electrophysiology recordings from SCN neurons in brain slices from Vipr2-/- (VPAC2 knockout) and Vipr2+/+ (wild-type) mice across the circadian cycle, measuring membrane properties, action potential thresholds, voltage-gated sodium currents, and responses to neurochemical mimics of light input.
Who was studied
VPAC2 receptor knockout and wild-type mice
What this study cannot tell us
Complete genetic knockout of VPAC2 is more extreme than any natural variation in VIP signaling — results may overestimate the impact of partial VIP dysfunction. Mouse SCN organization may differ from humans. Brain slice preparations remove the SCN from its normal context, though this is standard methodology.
How to read the evidence
Preliminary evidence from a rigorous electrophysiology study using genetic knockout mice. The findings are mechanistically clear but translation to human circadian disorders requires further research.
When this study was published
Published in 2024, advancing our understanding of the molecular basis of circadian timekeeping in the SCN.
The bigger picture
Circadian disruption is linked to obesity, diabetes, depression, cardiovascular disease, and even cancer. VIP-VPAC2 signaling is the master synchronizer of the body clock. This study shows exactly what goes wrong at the single-neuron level when that synchronization fails — providing potential therapeutic targets for the many diseases associated with circadian rhythm disruption.
Questions still open
- Could drugs that enhance VIP-VPAC2 signaling help resynchronize disrupted circadian rhythms in shift workers?
- Do partial reductions in VIP signaling (as might occur with aging) produce intermediate disruptions in SCN coordination?
- Is the missing sodium current component a direct consequence of VPAC2 loss or a downstream developmental effect?
Common questions
What does VIP do in the brain's clock?
Could problems with VIP explain why some people have trouble with sleep schedules?
Read the original research
Loss of neuropeptide signalling alters temporal expression of mouse suprachiasmatic neuronal state and excitability.
The European journal of neuroscience, 60(11), 6617-6633
Citation
Wegner, Sven; Belle, Mino D C; Chang, Pi-Shan; Hughes, Alun T L; Conibear, Alexandra E; Muir, Charlotte; Samuels, Rayna E; Piggins, Hugh D. (2024). Loss of neuropeptide signalling alters temporal expression of mouse suprachiasmatic neuronal state and excitability.. The European journal of neuroscience, 60(11), 6617-6633. https://doi.org/10.1111/ejn.16590