Beta-adrenergic receptor in the brain: comparison of 3H-dihydroalprenolol binding sites and a beta-adrenergic receptor regulating adenylyl cyclase activity in cell free homogenates. |
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Authors: | T E Cote J W Kebabian |
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Institution: | Biochemical Neuropharmacology Unit, Experimental Therapeutics Branch National Institute of Neurological and Communicative Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20014, USA |
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Abstract: | The properties of specific 3H-dihydroalprenolol binding sites resemble the properties of the beta-receptor regulating hormone-sensitive adenylyl cyclase activity in an homogenate of rabbit cerebellum. The rabbit cerebellum has 5 to 6 pmole per gm (wet weight) of high affinity (KD=1.3 nM) specific binding sites for 3H-dihydroalprenolol. the interaction of several beta-adrenergic agonists and antagonists with the specific binding sites is rapid, reversible, and demonstrates stereospecificity which parallels the properties of the beta receptor. Beta-adrenergic agonists show a similar potency as agonists upon adenylyl cyclase activity and as inhibitors of 3H-dihydroalprenolol binding: i.e. l-isoproterenol > l-epinephrine > l-norepinephrine (suggesting a beta2 adrenergic receptor). The binding affinities of several beta-adrenergic agonists and antagonists for the specific binding sites approximate the affinities of these compounds for the stimulation of adenylyl cyclase. Thus, the 3H-dihydroalprenolol binding sites have properties similar to the beta-adrenergic receptor regulating adenylyl cyclase activity in a rabbit cerebellar homogenate. |
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