Brain oxidation is an initial process in sleep induction.
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.
Ikeda
M
M
Department of Molecular Behavioral Biology, Osaka Bioscience Institute, 6-2-4 Furuedai, Suita, Osaka 565-0874, Japan. msikeda@obi.or.jp
Ikeda-Sagara
M
M
Okada
T
T
Clement
P
P
Urade
Y
Y
Nagai
T
T
Sugiyama
T
T
Yoshioka
T
T
Honda
K
K
Inoué
S
S
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
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