Relationship of atypical melatonin rhythm with two circadian clock outputs in B6D2F1 mice

• Published in: American journal of physiology. Regulatory, integrative and comparative physiology Vol. 278; no. 4; p. 924
• Main Authors: Li, Xiao-Mei, Liu, Xu-Hui, Filipski, Elisabeth, Metzger, Gerard, Delagrange, Philippe, Jeanniot, Jean-Philippe, Levi, Francis
• Format: Journal Article
• Language: English
• Published: 01.04.2000
• ISSN: 0363-6119; 1522-1490
• DOI: 10.1152/ajpregu.2000.278.4.r924

1  Laboratoire "Rythmes Biologiques and Chronothérapeutique," Institut du Cancer et d'Immunogénétique et Université Paris XI, Hôpital Paul Brousse, 94807 Villejuif Cedex; 2  Institut de Recherches Internationales Servier, 92415 Courbevoie; and 3  Technologie Servier, 45000 Orléans, France 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. circadian rhythms; body temperature; locomotor activity; pineal gland