Endogenous dopamine (DA) competes with the binding of a radiolabeled D₃ receptor partial agonist in vivo: a positron emission tomography study.
A series of microPET imaging studies were conducted in anesthetized rhesus monkeys using the dopamine D₃-selective partial agonist, [¹⁸F]5. There was variable uptake in regions of brain known to express a high density of D₃ receptors under baseline conditions. Pretreatment with lorazepam (1 mg/kg, i.v. 30 min) to reduce endogenous dopamine activity before tracer injection resulted in a dramatic increase in uptake in the caudate, putamen, and thalamus, and an increase in the binding potential (BP) values, a measure of D₃ receptor binding in vivo. These data indicate that there is a high level of competition between [¹⁸F]5 and endogenous dopamine for D₃ receptors in vivo.
Division of Radiological Sciences, Washington University School of Medicine, Mallinckrodt Institute of Radiology, Missouri 63110, USA. rhmach@mir.wustl.edu
Robert H
RH
Mach
Zhude
Z
Tu
Jinbin
J
Xu
Shihong
S
Li
Lynne A
LA
Jones
Michelle
M
Taylor
Robert R
RR
Luedtke
Colin P
CP
Derdeyn
Joel S
JS
Perlmutter
Mark A
MA
Mintun
D000818:Animals; D001549:Benzamides / Q000138:chemical synthesis / Q000493:pharmacokinetics; D001667:Binding, Competitive; D001921:Brain / Q000000981:diagnostic imaging* / Q000378:metabolism; D004298:Dopamine / Q000493:pharmacokinetics*; D018491:Dopamine Agonists / Q000138:chemical synthesis / Q000493:pharmacokinetics*; D005462:Fluorine Radioisotopes / Q000493:pharmacokinetics; D008253:Macaca mulatta; D008297:Male; D010879:Piperazines / Q000138:chemical synthesis / Q000493:pharmacokinetics; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals / Q000138:chemical synthesis / Q000493:pharmacokinetics*; D050637:Receptors, Dopamine D3 / Q000378:metabolism
D001549:Benzamides; D018491:Dopamine Agonists; D005462:Fluorine Radioisotopes; D010879:Piperazines; D019275:Radiopharmaceuticals; D050637:Receptors, Dopamine D3; D004298:Dopamine