title: Daily melatonin intake resets circadian rhythms of a sighted man with non-24-hour sleep-wake syndrome who lacks the nocturnal melatonin rise.
abstract: Effects of daily melatonin intake on the circadian rhythms of sleep and wakefulness, rectal temperature and plasma cortisol were examined in a sighted man who had suffered from the non-24-hour sleep-wake syndrome. The subject lacked the nocturnal melatonin rise in plasma, but showed robust circadian rhythms in rectal temperature and plasma cortisol. The sleep-wake rhythm free-ran with a period longer than 24 hours. Daily melatonin intake at 21:00 h concentrated sleep episodes in the nocturnal period (24:00-8:00 h), and increased the length of the episodes. A single oral dose (3 mg) of melatonin increased plasma melatonin levels to about 1300 pg/mL within one hour and remained at pharmacological levels for approximately 6 hours. The trough of rectal temperature and the circadian rise of plasma cortisol were fixed to the early morning. A higher dose of melatonin (6 mg) did not improve the general feature. After the cessation of melatonin intake, the sleep-wake rhythm began to free-run together with the circadian rhythms in rectal temperature and plasma cortisol. It is concluded that daily intake of melatonin at early night time resets the circadian rhythms in a sighted man who lacked the nocturnal melatonin rise and showed free-running circadian rhythms in routine life.
authors.affiliation: Department of Physiology, Hokkaido University School of Medicine, Sapporo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Nakamura
authors.forename: S
authors.initials: S
authors.lastname: Hashimoto
authors.forename: S
authors.initials: S
authors.lastname: Honma
authors.forename: K
authors.initials: K
authors.lastname: Honma
mesh_terms: D000284:Administration, Oral; D000328:Adult; D001831:Body Temperature / Q000502:physiology*; D002940:Circadian Rhythm / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D008137:Longitudinal Studies; D008297:Male; D008550:Melatonin / Q000008:administration & dosage* / Q000378:metabolism; D012007:Rectum; D012894:Sleep Stages / Q000187:drug effects* / Q000502:physiology; D012893:Sleep Wake Disorders / Q000188:drug therapy*
chemical_list: D008550:Melatonin; D006854:Hydrocortisone