title: Alpha-1 adrenergic receptors in the medial preoptic area are involved in the induction of sleep.
abstract: This paper reviews the recent studies that led to the conclusion that the noradrenergic neurons projecting to the medial preoptic area (mPOA) are hypnogenic and that they mediate this action through alpha(1) adrenergic receptors. Microinjection of noradrenaline (NA) into the mPOA induced arousal. Studies using alpha(2) adrenergic drugs showed that the arousal induced by intrapreoptic injection of NA was due to its action on presynaptic alpha(2) adrenergic receptors. A combination of lesion and chemical stimulation techniques demonstrated that when NA acted on the postsynaptic alpha(1 )receptors in the mPOA, it induced sleep. Intrapreoptic injection of alpha(1) agonist, methoxamine could induce sleep, when the hypothermia, which was simultaneously produced, was behaviorally compensated for by the animal. Increased arousal produced by the destruction of noradrenergic fibers in the mPOA further confirmed the hypnogenic role of these fibers.
authors.affiliation: Department of Physiology, All India Institute of Medical Sciences, New Delhi 110029, India. v_mohan_kumar@hotmail.com
authors.forename: Velayudhan Mohan
authors.initials: VM
authors.lastname: Kumar
authors.forename: Ramalingam
authors.initials: R
authors.lastname: Vetrivelan
authors.forename: Hruda Nanda
authors.initials: HN
authors.lastname: Mallick
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D001143:Arousal / Q000502:physiology; D005260:Female; D008297:Male; D008729:Methoxamine / Q000494:pharmacology; D008845:Microinjections; D009638:Norepinephrine / Q000494:pharmacology; D011301:Preoptic Area / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D018340:Receptors, Adrenergic, alpha-1 / Q000378:metabolism*; D018341:Receptors, Adrenergic, alpha-2 / Q000378:metabolism; D012726:Sexual Behavior, Animal / Q000502:physiology; D012890:Sleep / Q000502:physiology*; D013696:Temperature
chemical_list: D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D018340:Receptors, Adrenergic, alpha-1; D018341:Receptors, Adrenergic, alpha-2; D008729:Methoxamine; D009638:Norepinephrine