title: The Role of the Melatoninergic System in Light-Entrained Behavior of Mice.
abstract: The role of endogenous melatonin for the control of the circadian system under entrained conditions and for the determination of the chronotype is still poorly understood. Mice with deletions in the melatoninergic system (melatonin deficiency or the lack of melatonin receptors, respectively) do not display any obvious defects in either their spontaneous (circadian) or entrained (diurnal) rhythmic behavior. However, there are effects that can be detected by analyzing the periodicity of the locomotor behaviors in some detail. We found that melatonin-deficient mice (C57Bl), as well as melatonin-proficient C3H mice that lack the melatonin receptors (MT) 1 and 2 (C3H MT1,2 KO), reproduce their diurnal locomotor rhythms with significantly less accuracy than mice with an intact melatoninergic system. However, their respective chronotypes remained unaltered. These results show that one function of the endogenous melatoninergic system might be to stabilize internal rhythms under conditions of a steady entrainment, while it has no effects on the chronotype.
authors.affiliation: Dr. Senckenbergische Anatomie II, Fachbereich Medizin, Goethe-Universität Frankfurt, Theodor-Stern-Kai 7, D-60590 Frankfurt am Main, Germany. M.Pfeffer@em.uni-frankfurt.de.|Dr. Senckenbergisches Chronomedizinisches Institut, Goethe-Universität Frankfurt, Theodor-Stern-Kai 7, D-60590 Frankfurt am Main, Germany. M.Pfeffer@em.uni-frankfurt.de.
authors.forename: Martina
authors.initials: M
authors.lastname: Pfeffer
authors.affiliation: Dr. Senckenbergische Anatomie II, Fachbereich Medizin, Goethe-Universität Frankfurt, Theodor-Stern-Kai 7, D-60590 Frankfurt am Main, Germany. Korf@em.uni-frankfurt.de.|Dr. Senckenbergisches Chronomedizinisches Institut, Goethe-Universität Frankfurt, Theodor-Stern-Kai 7, D-60590 Frankfurt am Main, Germany. Korf@em.uni-frankfurt.de.
authors.forename: Horst-Werner
authors.initials: HW
authors.lastname: Korf
authors.affiliation: Dr. Senckenbergische Anatomie II, Fachbereich Medizin, Goethe-Universität Frankfurt, Theodor-Stern-Kai 7, D-60590 Frankfurt am Main, Germany. wicht@em.uni-frankfurt.de.
authors.forename: Helmut
authors.initials: H
authors.lastname: Wicht
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D002940:Circadian Rhythm; D008027:Light; D008297:Male; D008550:Melatonin / Q000096:biosynthesis* / Q000172:deficiency; D051379:Mice; D018345:Mice, Knockout; D009043:Motor Activity; D044122:Receptor, Melatonin, MT1 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D044123:Receptor, Melatonin, MT2 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism
chemical_list: D044122:Receptor, Melatonin, MT1; D044123:Receptor, Melatonin, MT2; D008550:Melatonin
keywords: chronotype; circadian; diurnal; locomotor rhythm; melatonin; stability