Evening melatonin and bright light administration induce additive phase shifts in dim light melatonin onset.
In healthy young men, administration of a single light pulse (5000 lux for 3 hr) or a single melatonin pill (5 mg) at 20:40 hr under controlled constant routine conditions of <10 lux, yielded a phase delay and a phase advance, respectively, in the circadian marker of dim light melatonin onset 24 hr later. Phase shifts after combining the two interventions were additive. Melatonin suppression is not necessary for a phase shift by light, and melatonin is not a 'weak' Zeitgeber relative to bright light when ambient lighting is strictly controlled.
Wirz-Justice
Anna
A
Centre for Chronobiology, Psychiatric University Clinic, Basel, Switzerland. anna.wirz-justice@unibas.ch
Kräuchi
Kurt
K
Cajochen
Christian
C
Danilenko
Konstantin V
KV
Renz
Claudia
C
Weber
Jakob M
JM
D000328:Adult; D002940:Circadian Rhythm / Q000502:physiology*; D018592:Cross-Over Studies; D006801:Humans; D008027:Light; D008297:Male; D008550:Melatonin / Q000097:blood*
D008550:Melatonin