Non‐photic phase shifting of the circadian clock: role of the extracellular signal‐responsive kinases I/II/mitogen‐activated protein kinase pathway
Bibliographic record
Abstract
The master circadian clock, located in the suprachiasmatic nucleus (SCN), is synchronized to the external world primarily through exposure to light. A second class of stimuli based on arousal or activity can also reset the hamster circadian clock in a manner distinct from light. The mechanism underlying these non-photic phase shifts is unknown, although suppression of canonical clock genes and immediate early genes has been implicated. Recently, suppression of one of the mitogen-activated protein kinases (MAPK), namely extracellular signal-responsive kinases I/II (ERK), has been implicated in phase shifts to dark pulses, a stimulus with both photic and non-photic components. We investigated the involvement of the ERK/MAPK pathway in phase shifts in response to 3 h of sleep deprivation initiated at mid-day. About three-quarters of animals subjected to this procedure demonstrated large phase advances of about 3 h. Those that shifted exhibited a significant decrease in phosphorylated ERK (p-ERK) in the SCN. Those animals that were perfused during the sleep deprivation also exhibited immunoreactivity for p-ERK in a distinct portion of the ventrolateral SCN. Finally, injections of U0126 to the SCN to prevent phosphorylation of ERK significantly decreased levels of p-ERK but did not produce phase shifts. These data demonstrate that a purely non-photic manipulation is able to alter the activity of the MAPK pathway in the SCN, with downregulation in the SCN shell and activation in a portion of the SCN core.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".