title: Relationship of atypical melatonin rhythm with two circadian clock outputs in B6D2F(1) mice.
abstract: Circadian rhythms in body temperature, locomotor activity, and the circadian changes of plasma and pineal melatonin content were investigated in B6D2F(1) mice synchronized by 12 h of light and 12 h of darkness. During 8 wk continuous recording, activity and temperature displayed a marked stable and reproducible circadian rhythm, with both peaks occurring near the middle of darkness. Both 24- and 12-h rhythmic components were also significantly detected. Mean plasma melatonin concentration rose steadily during the light span and reached a maximum (30.6 +/- 10.0 pg/ml) at 11 h after light onset (HALO), then gradually decreased after the onset of darkness to a nadir (4.7 +/- 0.4 pg/ml) at 20 HALO. Mean pineal content followed a pattern parallel to that of plasma concentration (peak at 11 HALO: 17.7 +/- 1.0 pg/gland; trough at 17 HALO: 4.7 +/- 1.0 pg/gland). In addition, a second sharp peak was observed at 21 HALO (20.2 +/- 3.5 pg/gland). Plasma and pineal contents displayed large and statistically significant circadian changes, with a composite rhythm of period (24 + 12 h). This mouse model has predominant production and secretion of melatonin during the day. This possibly contributes to a similar coupling between chronopharmacology mechanisms and the rest-activity cycle in these mice and in human subjects.
authors.affiliation: Laboratoire "Rythmes Biologiques and Chronothérapeutique," Institut du Cancer et d'Immunogénétique et Université Paris XI, Hôpital Paul Brousse, 94807 Villejuif Cedex, France.
authors.forename: X M
authors.initials: XM
authors.lastname: Li
authors.forename: X H
authors.initials: XH
authors.lastname: Liu
authors.forename: E
authors.initials: E
authors.lastname: Filipski
authors.forename: G
authors.initials: G
authors.lastname: Metzger
authors.forename: P
authors.initials: P
authors.lastname: Delagrange
authors.forename: J P
authors.initials: JP
authors.lastname: Jeanniot
authors.forename: F
authors.initials: F
authors.lastname: Lévi
mesh_terms: D000818:Animals; D001831:Body Temperature / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D008124:Locomotion / Q000502:physiology; D008297:Male; D008550:Melatonin / Q000032:analysis / Q000097:blood* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D010870:Pineal Gland / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D012146:Rest / Q000502:physiology; D013045:Species Specificity
chemical_list: D008550:Melatonin