Binding of (+)PHNO and other D2-dopamine agonists to D1-dopamine receptors labelled by [3H]SCH 23390

Abstract

The affinity of (+)PHNO for the D₁-dopamine receptor subtype in striatal tissue was determined in a radioligand binding assay using the D₁-selective compound, [³H]SCH 23390. The IC₅₀ for (+)PHNO was 22ΜM, a value considerably higher than obtained for reference agents (lisuride, apomorphine, pergolide, [−]EOE and bromocriptine). The low potency of (+)PHNO at the D₁-receptor subtype contrasts with the compound's high potency at the D₂-receptor subtype, as reported previously. (+)PHNO can, therefore, be classified as a very selective D₂-receptor agonist.