Melanopsin (Opn4) requirement for normal light-induced circadian phase shifting.
Level 5 - mechanism / opinion, no new human data
Animal knockout experiment (non-human laboratory research)
PubMed 12481141 · doi:10.1126/science.1076848
What was done
Researchers generated melanopsin-knockout mice (Opn4-/-) and assessed their circadian activity rhythms under standard light/dark cycles, constant darkness, and in response to brief pulses of monochromatic light.
What was found
The abstract reports no numerical values. Qualitatively, Opn4-/- mice successfully entrained to standard light/dark cycles and displayed no overt defects in circadian rhythms in constant darkness, but they showed severely attenuated phase resetting in response to brief monochromatic light pulses.
Why it matters
This study provides direct functional evidence that melanopsin is a critical photopigment for acute light-induced phase shifting of the mammalian circadian pacemaker.
Limits
The study was conducted in a mouse model, and the abstract does not provide sample sizes, quantitative effect sizes, variance measures, or specific light pulse parameters (intensity, wavelength, duration).
Cited by
- supports Melanopsin was discovered as a circadian photopigment in 2001 by three independent research groups.