title: Isolation of an endogenous clonidine-displacing substance from rat brain.
abstract: An endogenous substance which specifically displaces clonidine, yohimbine and rauwolscine from rat brain alpha 2-adrenergic receptors, has been isolated. The new compound, designed clonidine-displacing-substance (CDS), has been partially purified by ion exchange chromatography, zone electrophoresis and high performance liquid chromatography (HPLC). CDS binds specifically to alpha 2-adrenergic receptors by competing with either alpha 2-adrenergic agonists or alpha 2-antagonists, but has no effect on the specific binding of [3H]prazosin to alpha 1-adrenergic receptors in rat brain membranes. In the course of isolation, CDS was shown to be neither the endogenous neurotransmitter (-)norepinephrine (NE) nor the guanyl nucleotide GTP which lowers the specific binding of alpha 2-agonists to the alpha 2-adrenergic receptors.
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D001923:Brain Chemistry; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D003000:Clonidine / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004586:Electrophoresis; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*
chemical_list: D011942:Receptors, Adrenergic, alpha; D003000:Clonidine