title: Agmatine: an endogenous clonidine-displacing substance in the brain.
abstract: Clonidine, an antihypertensive drug, binds to alpha 2-adrenergic and imidazoline receptors. The endogenous ligand for imidazoline receptors may be a clonidine-displacing substance, a small molecule isolated from bovine brain. This clonidine-displacing substance was purified and determined by mass spectroscopy to be agmatine (decarboxylated arginine), heretofore not detected in brain. Agmatine binds to alpha 2-adrenergic and imidazoline receptors and stimulates release of catecholamines from adrenal chromaffin cells. Its biosynthetic enzyme, arginine decarboxylase, is present in brain. Agmatine, locally synthesized, is an endogenous agonist at imidazoline receptors, a noncatecholamine ligand at alpha 2-adrenergic receptors and may act as a neurotransmitter.
authors.affiliation: Department of Neurology and Neuroscience, Cornell University Medical College, New York, NY 10021.
authors.forename: G
authors.initials: G
authors.lastname: Li
authors.forename: S
authors.initials: S
authors.lastname: Regunathan
authors.forename: C J
authors.initials: CJ
authors.lastname: Barrow
authors.forename: J
authors.initials: J
authors.lastname: Eshraghi
authors.forename: R
authors.initials: R
authors.lastname: Cooper
authors.forename: D J
authors.initials: DJ
authors.lastname: Reis
mesh_terms: D000313:Adrenal Medulla / Q000187:drug effects / Q000378:metabolism; D000376:Agmatine / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000201:enzymology / Q000378:metabolism; D001923:Brain Chemistry; D002262:Carboxy-Lyases / Q000378:metabolism; D002417:Cattle; D002540:Cerebral Cortex / Q000378:metabolism; D003000:Clonidine / Q000031:analogs & derivatives / Q000378:metabolism; D004837:Epinephrine / Q000378:metabolism; D054755:Imidazoline Receptors; D018377:Neurotransmitter Agents / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism; D011955:Receptors, Drug / Q000378:metabolism
chemical_list: D054755:Imidazoline Receptors; D018377:Neurotransmitter Agents; D011942:Receptors, Adrenergic, alpha; D011955:Receptors, Drug; D000376:Agmatine; C016986:apraclonidine; D002262:Carboxy-Lyases; C019722:arginine decarboxylase; D003000:Clonidine; D009638:Norepinephrine; D004837:Epinephrine