[3H]Spiroperidol binding in rat striatum: two high-affinity sites of differing selectivities.
[3H]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 [3H]spiroperidol binding are monophasic, revealing an apparently homogeneous set of sites with KD 0.6 +/- 0.3 nM and density 440 +/- 80 fmol/mg protein. However, equilibrium displacement studies of [3H]spiroperidol binding at this site indicate an alpha-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 KD 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 alpha-adrenergic component of spiroperidol binding.
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002090:Butyrophenones / Q000378:metabolism*; D003342:Corpus Striatum / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism; D005260:Female; D007700:Kinetics; D008566:Membranes / Q000378:metabolism; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism; D013134:Spiperone / Q000378:metabolism*
D002090:Butyrophenones; D011942:Receptors, Adrenergic, alpha; D013134:Spiperone; D004298:Dopamine