title: The characteristics of adrenoceptors in homogenates of human cerebral cortex labelled by (3H)-rauwolscine.
abstract: The alpha-2-adrenoceptor antagonist (3H)-rauwolscine has been used to label adrenoceptors in membranes from human cerebral cortex. The radioligand binds with high affinity (KD 2.08 nM) to a single population of sites with a density of 135 fmoles/mg protein. Adrenoceptor antagonists displaced binding in a simple monomolecular fashion with an order of affinity rauwolscine greater than yohimbine greater than phentolamine greater than corynanthine greater than prazosin indicating binding to alpha-2-adrenoceptors. Agonists displaced with an order of affinity clonidine greater than (-) adrenaline greater than (-) noradrenaline greater than dopamine greater than (-) isoprenaline but all displayed apparent Hill coefficients less than unity indicating heterogeneity of binding. The relatively high affinity of the alpha-1 antagonist prazosin for (3H)-rauwolscine binding sites in rat cerebral cortex was not observed in the human tissue which had pharmacological properties similar to those described previously in human platelet.
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000378:metabolism; D000317:Adrenergic alpha-Antagonists / Q000378:metabolism; D000368:Aged; D001792:Blood Platelets / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism*; D006801:Humans; D008875:Middle Aged; D011941:Receptors, Adrenergic / Q000378:metabolism*; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism; D014316:Tritium; D015016:Yohimbine / Q000378:metabolism*
chemical_list: D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D014316:Tritium; D015016:Yohimbine