Myocardial accumulation of a dopamine D2 receptor-binding radioligand, 2'-iodospiperone.
125I-2'-iodospiperone (2'-ISP), which has a high and selective affinity for dopamine D2 receptors, produced a high myocardial accumulation of radioactivity in the early phase after intravenous injection into mice. A human scintigraphic study also showed that the myocardium was clearly visualized soon after intravenous injection of the tracer. Analysis of the myocardial homogenate obtained from mice showed that 125I-2'-ISP was metabolically stable and was taken up the myocardium in its intact form. Administration of spiperone significantly reduced the myocardial uptake of 125I-2'-ISP in mice. Treatment with haloperidol and (+) butaclamol, which have a high affinity for dopamine D2 receptors, also tended to reduce the myocardial uptake of radioactivity, while (-)-butaclamol, which has no affinity for dopamine D2 receptors, caused no change in uptake. These findings suggest that the myocardial accumulation of 2'-ISP occurred in association with dopamine D2 (DA2) receptors.
Saji
H
H
Department of Radiopharmaceutical Chemistry, Faculty of Pharmaceutical Sciences, Kyoto University, Japan.
Yonekura
Y
Y
Tanahashi
K
K
Iida
Y
Y
Iwasaki
Y
Y
Magata
Y
Y
Konishi
J
J
Yokoyama
A
A
D000818:Animals; D002069:Butaclamol / Q000494:pharmacology; D006220:Haloperidol / Q000494:pharmacology; D006321:Heart / Q000000981:diagnostic imaging*; D007275:Injections, Intravenous; D007457:Iodine Radioisotopes; D008297:Male; D051379:Mice; D009206:Myocardium / Q000378:metabolism*; D011877:Radionuclide Imaging; D051381:Rats; D017448:Receptors, Dopamine D2 / Q000378:metabolism*; D013134:Spiperone / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D014018:Tissue Distribution
D007457:Iodine Radioisotopes; D017448:Receptors, Dopamine D2; C053751:2'-iodospiperone; D013134:Spiperone; D002069:Butaclamol; D006220:Haloperidol