Synthesis and biological evaluation of the binding of dopamine D2/D3 receptor agonist, (R,S)-5-hydroxy-2-(N-propyl-N-(5'-(18)F-fluoropentyl)aminotetralin ((18)F-5-OH-FPPAT) in rodents and nonhuman primates.
We have synthesized a new fluorinated dopamine D2 receptor agonist, (R,S)-2-(N-propyl-N-5'-fluoropentyl)amino-5-hydroxytetralin (5-OH-FPPAT). The radiosynthesis of the fluorine-18 analog, (18)F-5-OH-FPPAT was achieved in decay corrected yields of 10 to 15% in specific activities of approx. 1.5 to 2 Ci/micromol. In vitro binding and autoradiographic studies of this new radiotracer have been investigated. Using rat striatal homogenate binding assay, 5-OH-FPPAT exhibited an affinity of IC(50) = 6.95 nM. The octanol-buffer partition coefficient, Log P was found to be 1.60. In vitro autoradiographs in rat brain slices with (18)F-5-OH-FPPAT revealed selective binding to the dopaminergic regions in the striata that was displaceable by sulpiride. This selective binding to the striata was also removed in the presence of the GTP analog, 5'-guanylylimidodiphosphate, indicative of predominant binding of (18)F-5-OH-FPPAT to the high-affinity state of the D2 receptor. In vivo regional distribution of (18)F-5-OH-FPPAT in rat brains revealed selective localization in the striata with striata/cortex ratio of 1.5 and striata/cerebellum ratio of 1.8 to 2.0. The binding of (18)F-5-OH-FPPAT in the striata was reduced upon pretreatment with the antagonist, risperidone and the agonist, PPHT. A PET study in rhesus monkeys showed selective localization of (18)F-5-OH-FPPAT in the striata and the ratio between striata and cerebellum approached approximately 2 at 40 min post-injection.
Shi
Bingzhi
B
Department of Internal Medicine/Nuclear Medicine, Kettering Medical Center, Wright State University, Dayton, OH 45429, USA.
Narayanan
Tanjore K
TK
Christian
Bradley T
BT
Chattopadhyay
Sankha
S
Mukherjee
Jogeshwar
J
D000818:Animals; D001921:Brain / Q000000981:diagnostic imaging* / Q000378:metabolism*; D065127:Dopamine D2 Receptor Antagonists; D004353:Drug Evaluation, Preclinical; D006801:Humans; D007553:Isotope Labeling / Q000379:methods; D007700:Kinetics; D008253:Macaca mulatta; D008297:Male; D008657:Metabolic Clearance Rate; D049268:Positron-Emission Tomography / Q000379:methods*; D011323:Primates; D011485:Protein Binding; D019275:Radiopharmaceuticals / Q000138:chemical synthesis / Q000493:pharmacokinetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D017448:Receptors, Dopamine D2 / Q000378:metabolism*; D050637:Receptors, Dopamine D3; D012377:Rodentia; D013045:Species Specificity; D013764:Tetrahydronaphthalenes / Q000737:chemistry / Q000493:pharmacokinetics*; D014018:Tissue Distribution
C494119:5-hydroxy-2-(N-propyl-N-(5'-fluoropentyl))aminotetralin; C493593:DRD3 protein, human; D065127:Dopamine D2 Receptor Antagonists; C493595:Drd3 protein, rat; D019275:Radiopharmaceuticals; D017448:Receptors, Dopamine D2; D050637:Receptors, Dopamine D3; D013764:Tetrahydronaphthalenes