Radioreceptor binding reveals the potencies of N,N-disubstituted 2-aminotetralins as D2 dopamine agonists

The affinity of a series of N,N-disubstituted 2-aminotetralins for the rat striatal D₂ dopamine receptor labelled by [³H]spiperone has been determined. Displacement data for the more potent 2-aminotetralins were better described by a model where the compounds competed for [³H]spiperone at two sites. The high affinity component accounted for approximately 80% of the total sites. Displacement curves for all 2-aminotetralins were shifted to the right by 100 µM guanosine-5'-triphosphate; a result attributable to the redistribution of 13–47% of the sites to a low affinity form. These data are consistent with the N,N-disubstituted 2-aminotetralins being agonists at the D₂ dopamine receptor. In particular, the affinities of the 5-hydroxy-2-aminotetralins were as high as those of traditional dopamine agonists.