RT Journal Article
SR Electronic
T1 Beta Adrenergic Receptor Binding in Membrane Preparations from Mammalian Brain
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 568
OP 580
VO 12
IS 4
A1 BYLUND, DAVID B.
A1 SNYDER, SOLOMON H.
YR 1976
UL http://molpharm.aspetjournals.org/content/12/4/568.abstract
AB [3H]Dihydroalprenolol ([3H]DHA) binding sites in membrane preparations of rat and monkey brain appear to involve beta adrenergic receptors. [3H]DHA binding is saturable, with high affinity and an apparent dissociation constant of about 1 nM. Determination of the dissociation constant by kinetic studies measuring rate constants for association and dissociation provided KD values similar to those obtained in equilibrium experiments. [3H]DHA binding is stereospecific for adrenergic agonists and antagonists. The relative potencies of numerous drugs in competing for [3H]DHA binding sites parallel their pharmacological activity at beta receptors, and suggest that the receptors are of the beta1 type. Subcellular fractionation studies show an enrichment of [3H]DHA binding sites in "synaptic membrane" fractions. Regional distribution studies reveal fairly low densities of binding sites in the hypothalamus, which contains the highest norepinephrine concentration, suggesting that norepinephrine receptors in the hypothalamus are predominantly of the alpha variety. The relatively high levels of [3H]DHA binding in the cerebral cortex and cerebellum suggest that synaptic actions of norepinephrine in these regions may involve beta receptors. ACKNOWLEDGMENTS We wish to thank Mr. Robert Innis and Mr. Leigh Shuman for their competent assistance, and Dr. Michael J. Kuhar for dissecting the monkey brains.