title: Mammalian clock output mechanisms.
abstract: In mammals many behaviours (e.g. sleep-wake, feeding) as well as physiological (e.g. body temperature, blood pressure) and endocrine (e.g. plasma corticosterone concentration) events display a 24 h rhythmicity. These 24 h rhythms are induced by a timing system that is composed of central and peripheral clocks. The highly co-ordinated output of the hypothalamic biological clock not only controls the daily rhythm in sleep-wake (or feeding-fasting) behaviour, but also exerts a direct control over many aspects of hormone release and energy metabolism. First, we present the anatomical connections used by the mammalian biological clock to enforce its endogenous rhythmicity on the rest of the body, especially the neuro-endocrine and energy homoeostatic systems. Subsequently, we review a number of physiological experiments investigating the functional significance of this neuro-anatomical substrate. Together, this overview of experimental data reveals a highly specialized organization of connections between the hypothalamic pacemaker and neuro-endocrine system as well as the pre-sympathetic and pre-parasympathetic branches of the autonomic nervous system.
authors.affiliation: Division of Gastroenterology and Hepatology, Academic Medical Center (AMC), AZ, Amsterdam, The Netherlands. a.kalsbeek@amc.uva.nl
authors.forename: Andries
authors.initials: A
authors.lastname: Kalsbeek
authors.forename: Chun-Xia
authors.initials: CX
authors.lastname: Yi
authors.forename: Cathy
authors.initials: C
authors.lastname: Cailotto
authors.forename: Susanne E
authors.initials: SE
authors.lastname: la Fleur
authors.forename: Eric
authors.initials: E
authors.lastname: Fliers
authors.forename: Ruud M
authors.initials: RM
authors.lastname: Buijs
mesh_terms: D000818:Animals; D001341:Autonomic Nervous System / Q000502:physiology; D001683:Biological Clocks / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D003345:Corticosterone / Q000378:metabolism* / Q000502:physiology; D004703:Endocrine System / Q000378:metabolism / Q000502:physiology; D006801:Humans; D007031:Hypothalamus / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D013493:Suprachiasmatic Nucleus / Q000378:metabolism / Q000502:physiology*
chemical_list: D003345:Corticosterone