title: Preliminary evidence of a synergistic alpha 1- and beta 1-adrenoceptor regulation of rat pineal hydroxyindole-O-methyltransferase.
abstract: The activity of serotonin N-acetyltransferase in the rat pineal is regulated through a synergistic action of norepinephrine on alpha 1- and beta 1-adrenoceptors. Rat pineal hydroxyindole-O-methyltransferase (HIOMT) activity is also responsive to the beta 1-adrenoceptor, while melatonin synthesis and indoleamine release in certain species is apparently under alpha 1-adrenoceptor control. The present study reports that the simultaneous administration of doxazosin (a selective alpha 1-adrenergic antagonist) and metoprolol (a selective beta 1-adrenergic antagonist) reduces peak HIOMT activity significantly more than either agent alone, indicating that rat pineal HIOMT is also subject to synergistic alpha 1- and beta 1-adrenergic regulation. The relationship between alpha 1-adrenoceptor stimulation, serotonin release, and HIOMT activity is considered, following the observation that nocturnal HIOMT activity is elevated in serotonin-depleted pineal glands.
authors.affiliation: School of Biological Sciences, Macquarie University, North Ryde, New South Wales, Australia.
authors.forename: S D
authors.initials: SD
authors.lastname: McLeod
authors.forename: K D
authors.initials: KD
authors.lastname: Cairncross
mesh_terms: D000121:Acetylserotonin O-Methyltransferase / Q000378:metabolism*; D000375:Aging / Q000378:metabolism; D000818:Animals; D001835:Body Weight / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology; D017292:Doxazosin / Q000494:pharmacology; D010134:Fenclonine / Q000494:pharmacology; D008297:Male; D008550:Melatonin / Q000096:biosynthesis; D010870:Pineal Gland / Q000187:drug effects / Q000201:enzymology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018340:Receptors, Adrenergic, alpha-1 / Q000187:drug effects / Q000502:physiology*; D018342:Receptors, Adrenergic, beta-1 / Q000187:drug effects / Q000502:physiology*; D012701:Serotonin / Q000096:biosynthesis
chemical_list: D018340:Receptors, Adrenergic, alpha-1; D018342:Receptors, Adrenergic, beta-1; D012701:Serotonin; D000121:Acetylserotonin O-Methyltransferase; D008550:Melatonin; D017292:Doxazosin; D010134:Fenclonine