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

K. D. Burris, T. M. Filtz, S. Chumpradit, M. P. Kung, C. Foulon, J. G. Hensler, H. F. Kung, P. B. Molinoff

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53 Scopus citations


[125I](R,S)-trans-7-Hydroxy-2-[N-propyl-N-(3'-iodo-2'-propenyl)- amino]tetralin {[125I](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 serotonin(1A) receptors. Binding of [125I](R)-trans-7- OH-PIPAT to serotonin(1A) 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 K(d) 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.

Original languageEnglish (US)
Pages (from-to)935-942
Number of pages8
JournalJournal of Pharmacology and Experimental Therapeutics
Issue number2
StatePublished - 1994

ASJC Scopus subject areas

  • Molecular Medicine
  • Pharmacology

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