An endogenous substance which specifically displaces clonidine, yohimbine and rauwolscine from rat brain cyz-adrenergic receptors, has been isolated. The new compound, designed clonidine-displacingsubstance (CDS), has been partially purified by ion exchange chromatography, zone electrophoresis and high performance liquid chromatography (HPLC). CDS binds specifically to cYz-adrenergic receptors by competing with either cuz-adrenergic agonists or cYz-antagonists, but has no effect on the specific binding of [3H]prazosin to cYr-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 cYz-agonists to the cus-adrenergic receptors.
Clonidine cYrAdrenergic receptor Yohimbine