Affinities and intrinsic activities of dopamine receptor agonists for the hD21 and hD4.4 receptors

The affinity and intrinsic activity of dopamine receptor agonists were determined at the human dopamine hD21 and hD4.4 receptors. (−)-3-Hydroxy-N-n-propylpiperidine ((−)3-PPP) had an intrinsic activity of 46% and 83%, whereas (+)-N-propylnorapomorphine ((+)-NPA) had intrinsic activities of 61% and 58% at the dopamine hD21 and hD4.4 receptors, respectively. Affinities also varied. A single, or multiple, dopamine D2-type receptor(s) may be invoved in schizophrenia and agonists are being tested as therapy. Understanding their properties at the individual dopamine D2-family receptors is important.