[125I]SCH 23982, a 'selective' D-1 receptor antagonist, labels with high affinity 5-HT1C sites in pig choroid plexus

Abstract

[125I]SCH 23982, a ligand reported to be very selective for dopamine D-1 receptors, binds with high affinity to membranes of pig choroid plexus (KD = 186 pM, Bmax = 142 fmol/mg protein). Saturation and competition experiments suggested that [125I]SCH 23982 labels a homogeneous population of sites. The rank order for affinity of agonists, 5-HT ≥ DOI (1-(,5-dimethoxy-4-iodophenyl)-2-aminopropane) ≫ dopamine > fenoldopam, and antagonists, metergoline > mesulergine = mianserin > SCH 23390 > methiothepin > ketanserin > fluphenazine ≫ (-)-sulpiride > (+)-sulpiride, was compatible with labelling of 5-HT1C receptors by [125I]SCH 23982. It also correlates very significantly with [3H]mesulergine bindi..