In vitro evaluation of radioiodinated butyrophenones as radiotracer for dopamine receptor study.
Radioiodinated butyrophenone compounds are attracting the interest of those working on dopamine receptor studies; structure-activity relationship study has revealed the ortho position of the p-fluorobutyrophenone moiety as a very plausible iodination site. Various synthesized butyrophenones iodinated at the ortho position of p-fluorobutyrophenone moiety, 2'-iodohaloperidol (2'-IHP), 2'-iodotrifluperidol (2'-ITP) and 2'-iodospiperone (2'-ISP) were tested for their abilities to inhibit 3H-spiperone (SP) binding for the dopamine (D-2) receptor, together with reference compounds (SP, haloperidol(HP) and 4-iodospiperone (4-ISP]. The order of binding affinity of the tested compounds was SP greater than 2'-ISP greater than HP greater than 4-ISP greater than 2'-IHP greater than 2'-ITP. Whereas, the serotonin (S-2) receptor binding affinity of SP and its iodinated analogues were in the order of SP much greater than 4-ISP greater than 2'-ISP. Furthermore, in the saturation binding study using the striatal membrane preparations, the 2'-ISP displayed a KD of 0.25 nM with maximum number of binding site Bmax of 210 fmol/mg protein. These data indicated the 2'-ISP as holding high affinity for dopamine receptors and a low affinity for serotonin receptors. Thus, the 125I-2'-ISP was a very potent radioligand for in vitro dopamine (D-2) receptor studies, and 123I-2'-ISP holds very promising characteristics as for in vivo dopamine receptor studies, as well.
D000818:Animals; D001667:Binding, Competitive; D002090:Butyrophenones / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D003342:Corpus Striatum / Q000378:metabolism; D005260:Female; D007457:Iodine Radioisotopes; D007650:Ketanserin / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000378:metabolism*; D017448:Receptors, Dopamine D2; D011985:Receptors, Serotonin / Q000378:metabolism; D013134:Spiperone / Q000031:analogs & derivatives / Q000378:metabolism
D002090:Butyrophenones; D007457:Iodine Radioisotopes; D011954:Receptors, Dopamine; D017448:Receptors, Dopamine D2; D011985:Receptors, Serotonin; C053751:2'-iodospiperone; D013134:Spiperone; D007650:Ketanserin