@article {Burris935, author = {K D Burris and T M Filtz and S Chumpradit and M P Kung and C Foulon and J G Hensler and H F Kung and P B Molinoff}, title = {Characterization of [125I](R)-trans-7-hydroxy-2-[N-propyl-N-(3{\textquoteright}-iodo-2{\textquoteright}-propenyl)amino] tetralin binding to dopamine D3 receptors in rat olfactory tubercle.}, volume = {268}, number = {2}, pages = {935--942}, year = {1994}, publisher = {American Society for Pharmacology and Experimental Therapeutics}, abstract = {[125I](R,S)-trans-7-Hydroxy-2-[N-propyl-N-(3{\textquoteright}-iodo-2{\textquoteright}-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.}, issn = {0022-3565}, URL = {https://jpet.aspetjournals.org/content/268/2/935}, eprint = {https://jpet.aspetjournals.org/content/268/2/935.full.pdf}, journal = {Journal of Pharmacology and Experimental Therapeutics} }