title: The role of adenosine in the regulation of sleep.
abstract: This paper presents an overview of the current knowledge about the role of adenosine in the sleep-wake regulation with a focus on adenosine in the central nervous system, regulation of adenosine levels, adenosine receptors, and manipulations of the adenosine system by the use of pharmacological and molecular biological tools. The endogenous somnogen prostaglandin (PG) D(2) increases the extracellular level of adenosine under the subarachnoid space of the basal forebrain and promotes physiological sleep. Adenosine is neither stored nor released as a classical neurotransmitter and is thought to be formed inside cells or on their surface, mostly by breakdown of adenine nucleotides. The extracellular concentration of adenosine increases in the cortex and basal forebrain during prolonged wakefulness and decreases during the sleep recovery period. Therefore, adenosine is proposed to act as a homeostatic regulator of sleep and to be a link between the humoral and neural mechanisms of sleep-wake regulation. Both the adenosine A(1) receptor (A(1)R) and A(2A)R are involved in sleep induction. The A(2A)R plays a predominant role in the somnogenic effects of PGD(2). By use of gene-manipulated mice, the arousal effect of caffeine was shown to be dependent on the A(2A)R. On the other hand, inhibition of wake-promoting neurons via the A(1)R also mediates the sleep-inducing effects of adenosine, whereas activation of A(1)R in the lateral preoptic area induces wakefulness, suggesting that A(1)R regulates the sleep-wake cycle in a site-dependent manner. The potential therapeutic applications of agonists and antagonists of these receptors in sleep disorders are briefly discussed.
authors.affiliation: Department of Molecular Behavioral Biology, Osaka Bioscience Institute, Suita, Osaka 565-0874, Japan. huangzljp@yahoo.com.cn
authors.forename: Zhi-Li
authors.initials: ZL
authors.lastname: Huang
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Urade
authors.forename: Osamu
authors.initials: O
authors.lastname: Hayaishi
mesh_terms: D000241:Adenosine / Q000378:metabolism / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D018377:Neurotransmitter Agents / Q000378:metabolism / Q000494:pharmacology; D033703:Nucleoside Transport Proteins / Q000378:metabolism; D011301:Preoptic Area / Q000166:cytology / Q000378:metabolism; D015230:Prostaglandin D2 / Q000378:metabolism* / Q000494:pharmacology; D058906:Purinergic P1 Receptor Agonists / Q000494:pharmacology; D051381:Rats; D043682:Receptor, Adenosine A1 / Q000235:genetics / Q000378:metabolism*; D043705:Receptor, Adenosine A2A / Q000235:genetics / Q000378:metabolism*; D012890:Sleep / Q000187:drug effects / Q000502:physiology*; D020178:Sleep Disorders, Circadian Rhythm / Q000188:drug therapy / Q000503:physiopathology; D013346:Subarachnoid Space / Q000166:cytology / Q000378:metabolism; D009435:Synaptic Transmission; D014851:Wakefulness / Q000187:drug effects / Q000502:physiology*
chemical_list: D018377:Neurotransmitter Agents; D033703:Nucleoside Transport Proteins; D058906:Purinergic P1 Receptor Agonists; D043682:Receptor, Adenosine A1; D043705:Receptor, Adenosine A2A; C444719:adenosine transporter; D002110:Caffeine; D000255:Adenosine Triphosphate; D000241:Adenosine; D015230:Prostaglandin D2