title: Brain oxidation is an initial process in sleep induction.
abstract: CNS activity is generally coupled to the vigilance state, being primarily active during wakefulness and primarily inactive during deep sleep. During periods of high neuronal activity, a significant volume of oxygen is used to maintain neuronal membrane potentials, which subsequently produces cytotoxic reactive oxygen species (ROS). Glutathione, a major endogenous antioxidant, is an important factor protecting against ROS-mediated neuronal degeneration. Glutathione has also been proposed to be a sleep-promoting substance, yet the relationship between sleep and cerebral oxidation remains unclear. Here we report that i.c.v. infusion of the organic peroxide t-butyl-hydroperoxide at a concentration below that triggering neurodegeneration (0.1 micromol/100 microl/10 h) promotes sleep in rats. Also, microinjection (2 nmol, 2 microl) or microdialysis (100 microM, 20 min) of t-butyl-hydroperoxide into the preoptic/anterior hypothalamus (POAH) induces the release of the sleep-inducing neuromodulators, nitric oxide and adenosine, without causing neurodegeneration. Nitric oxide and adenosine release was inhibited by co-dialysis of the N-methyl-D-aspartate receptor antagonist, d(-)-2-amino-5-phosphonopentanoic acid (D-AP5; 1 mM), suggesting that glutamate-induced neuronal excitation mediates the peroxide-induced release of nitric oxide and adenosine. Indeed, Ca2+ release from mitochondria and delayed-onset Ca2+ influx via N-methyl-D-aspartate receptors was visualized during peroxide exposure using Ca2+ indicator proteins (YC-2.1 and mitochondrial-targeted Pericam) expressed in organotypic cultures of the POAH. In the in vitro models, t-butyl-hydroperoxide (50 microM) causes dendritic swelling followed by the intracellular Ca2+ mobilization, and D-AP5 (100 microM) or glutathione (500 microM) inhibited t-butyl-hydroperoxide-induced intracellular Ca2+ mobilization and protected POAH neurons from oxidative stress. These data suggest that low-level subcortical oxidation under the control of an antioxidant system may trigger sleep via the Ca(2+)-dependent release of sleep-inducing neuromodulators in the POAH, and thus we propose that a moderate increase of ROS during wakefulness in the neuronal circuits regulating sleep may be an initial trigger in sleep induction.
authors.affiliation: Department of Molecular Behavioral Biology, Osaka Bioscience Institute, 6-2-4 Furuedai, Suita, Osaka 565-0874, Japan. msikeda@obi.or.jp
authors.forename: M
authors.initials: M
authors.lastname: Ikeda
authors.forename: M
authors.initials: M
authors.lastname: Ikeda-Sagara
authors.forename: T
authors.initials: T
authors.lastname: Okada
authors.forename: P
authors.initials: P
authors.lastname: Clement
authors.forename: Y
authors.initials: Y
authors.lastname: Urade
authors.forename: T
authors.initials: T
authors.lastname: Nagai
authors.forename: T
authors.initials: T
authors.lastname: Sugiyama
authors.forename: T
authors.initials: T
authors.lastname: Yoshioka
authors.forename: K
authors.initials: K
authors.lastname: Honda
authors.forename: S
authors.initials: S
authors.lastname: Inoué
mesh_terms: D000241:Adenosine / Q000378:metabolism; D000818:Animals; D007025:Anterior Hypothalamic Nucleus / Q000187:drug effects / Q000378:metabolism; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism / Q000494:pharmacology; D008297:Male; D008869:Microtubule-Associated Proteins / Q000187:drug effects / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D009924:Organ Culture Techniques; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D010101:Oxygen Consumption / Q000502:physiology*; D011301:Preoptic Area / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism*; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000378:metabolism; D012890:Sleep / Q000187:drug effects / Q000502:physiology*; D020122:tert-Butylhydroperoxide / Q000494:pharmacology
chemical_list: D018691:Excitatory Amino Acid Antagonists; C489787:MAP2 protein, rat; D008869:Microtubule-Associated Proteins; D017382:Reactive Oxygen Species; D016194:Receptors, N-Methyl-D-Aspartate; D009569:Nitric Oxide; D018698:Glutamic Acid; D020122:tert-Butylhydroperoxide; D005978:Glutathione; D000241:Adenosine; D002118:Calcium