In vivo displacement by 3-PPP enantiomers of N,N-dipropyl-5,6-ADTN from dopamine receptor-binding sites in rat striatum

J Neural Transm. 1985;64(3-4):173-85. doi: 10.1007/BF01256465.


The enantiomers of 3-PPP or haloperidol were injected in various doses to rats 1 hour after the established dopamine receptor ligand N,N-dipropyl-5,6-ADTN. After another 40 minutes the binding of the ligand to the striatum was measured by high performance liquid chromatography, using the level in the cerebellum as "blank". (-)-3-PPP was found to cause a maximum 71% displacement of the ligand from the striatal binding sites. Haloperidol proved to be more potent but not significantly more efficacious in displacing the ligand. However, the combined treatment with (-)-3-PPP and haloperidol caused a stronger displacement of the ligand than (-)-3-PPP alone, suggesting that the binding-site populations available for the two agents are not fully identical. (+)-3-PPP also caused displacement of the ligand but was considerably less potent than its enantiomeric twin. The results are discussed against the background of the different pharmacological profiles of the 3-PPP enantiomers and haloperidol. It is suggested that an inverse relationship may exist between receptor affinity and intrinsic activity and that such a relationship may be inherent in the mechanism underlying receptor stimulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Binding, Competitive
  • Brain / metabolism*
  • Cerebellum / metabolism
  • Corpus Striatum / metabolism
  • Haloperidol / metabolism*
  • Isomerism
  • Male
  • Naphthalenes / metabolism*
  • Piperidines / metabolism*
  • Rats
  • Rats, Inbred Strains
  • Receptors, Dopamine / metabolism*
  • Tetrahydronaphthalenes / metabolism*


  • Naphthalenes
  • Piperidines
  • Receptors, Dopamine
  • Tetrahydronaphthalenes
  • 2-(N,N-dipropyl)amino-5,6-dihydroxytetralin
  • preclamol
  • Haloperidol