Affinities and intrinsic activities of dopamine receptor agonists for the hD(21) and hD(4.4) receptors

The affinity and intrinsic activity of dopamine receptor agonists were determined at the human dopamine hD(21) and hD(4.4) 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 hD(21) and hD(4.4) receptors, respectively. Affinities also varied. A single, or multiple, dopamine D-2-type receptor(s) may be involved in schizophrenia and agonists are being tested as therapy. Understanding their properties at the individual dopamine D-2-family receptors is important.