Characterization of [125I](R)-trans-7-hydroxy-2-[N-propyl-N-(3'-iodo-2'-propenyl)amino] tetralin binding to dopamine D3 receptors in rat olfactory tubercle

J Pharmacol Exp Ther. 1994 Feb;268(2):935-42.

Abstract

[125I](R,S)-trans-7-Hydroxy-2-[N-propyl-N-(3'-iodo-2'-propenyl)- amino]tetralin ([125](R,S)-trans-7-OH-PIPAT) has been shown to bind with high affinity to dopamine D3 receptors expressed in Spodoptera frugiperda cells. No specific binding was seen in Spodoptera frugiperda cells expressing a high density of D2 receptors. It was therefore, suggested that [125I] (R,S)-trans-7-OH-PIPAT selectively labels D3 receptors. In the present study, saturation binding of [125I](R)-trans-7-OH-PIPAT to membranes from rat olfactory tubercle resulted in markedly curvilinear Scatchard plots, suggesting that the radioligand was binding to more than one receptor class or affinity state. [125I] (R)-trans-7-OH-PIPAT bound with high affinity to membranes from human embryonic kidney-293 cells expressing transfected D2 or D3 receptors and to membranes from Chinese hamster ovary cells expressing serotonin1A receptors. Binding of [125I](R)-trans-7-OH-PIPAT to serotonin1A and D2 receptors was decreased or eliminated in the presence of NaCl and/or guanylyl-imidodiphosphate [Gpp(NH)p]. In the presence of Gpp(NH)p and NaCl, a linear Scatchard plot with a Kd value of 0.4 nM and a density of 100 fmol/mg of protein was obtained in membranes from rat olfactory tubercle. Agonists and antagonists inhibited binding of [125I](R)-trans-7-OH-PIPAT with a rank order of potency consistent with an interaction at D3 receptors. These results suggest that, in the presence of Gpp(NH)p and NaCl, [125I](R)-trans-7-OH-PIPAT specifically labels D3 receptors.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cell Line
  • Guanylyl Imidodiphosphate / pharmacology
  • Humans
  • Olfactory Pathways / metabolism*
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Dopamine / genetics
  • Receptors, Dopamine / metabolism*
  • Receptors, Dopamine D2 / metabolism
  • Receptors, Dopamine D3
  • Receptors, Serotonin / metabolism
  • Sodium Chloride / pharmacology
  • Tetrahydronaphthalenes / metabolism*
  • Transfection

Substances

  • DRD3 protein, human
  • Drd3 protein, rat
  • Receptors, Dopamine
  • Receptors, Dopamine D2
  • Receptors, Dopamine D3
  • Receptors, Serotonin
  • Tetrahydronaphthalenes
  • 7-hydroxy-2-(N-n-propyl-N-(3-iodo-2'-propenyl)-amino)tetralin
  • Guanylyl Imidodiphosphate
  • Sodium Chloride