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3 H]Spiroperidol Binding in Rat Striatum: Two High‐Affinity Sites of Differing Selectivities
Author(s) -
Andorn Anne C.,
Maguire Michael E.
Publication year - 1980
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1980.tb07865.x
Subject(s) - saturation vapor curve , dopaminergic , chemistry , striatum , binding site , membrane , saturation (graph theory) , dopamine , spiperone , biophysics , biochemistry , biology , endocrinology , dopamine receptor , enzyme , receptor , mathematics , combinatorics
[ 3 H]Spiroperidol binding to homogenates of rat striatum is saturable and shows either monophasic or biphasic saturation isotherms under specified conditions. In poorly washed membrane fragment preparations, saturation isotherms of [ 3 H]spiroperidol binding are monophasic, revealing an apparently homogeneous set of sites with K p 0.6 ± 0.3 nm and density 440 ± 80 fmol/mg protein. However, equilibrium displacement studies of [ 3 H]spiroperidol binding at this site indicate an a‐adrenergic component in addition to the previously described dopaminergic component. In thoroughly washed membrane fragment preparations, saturation isotherms are clearly biphasic, showing an additional high‐affinity site with an approximate K D of 24 ±10 pm and an approximate density of 110 ± 20 fmol/mg protein at a protein concentration of 2.0 mg/ml. Selectivity at this site appears classically dopaminergic, suggesting that the lower affinity site is the primary source of the α‐adrenergic component of spiroperidol binding.