title: 125I-Spiperone: a novel ligand for D2 dopamine receptors.
abstract: 125I-Spiperone binds with high affinity (KD 0.3 nM) to a single specific site (Bmax 34 pmol/g wet weight) in homogenates of rat corpus striatum. Specific binding is about 40-60 percent of total binding and is displaced stereo-specifically by butaclamol and clopenthixol. Neuroleptic drugs of various classes are potent inhibitors of 125I-spiperone binding (Ki's 1-10 nM). Selective dopamine antagonists such as sulpiride (Ki 50 nM) and dopamine agonists such as apomorphine (Ki 200 nM) are also potent inhibitors. The drug specificity of 125I-spiperone binding correlates well with that of 3H-spiperone binding, providing good evidence that 125I-spiperone labels D2 dopamine receptors in striatal membranes. 125I-Spiperone, with its high specific activity (2200 Ci/mmol) may prove to be a useful ligand in studies examining D2 dopamine receptors in soluble preparations and by autoradiography. Furthermore iodinated spiperone may be useful in radioreceptor assays of neuroleptic drug levels and, in a 123I-labeled form, for imaging of dopamine receptors, in vivo, using single photon tomography.
mesh_terms: D000818:Animals; D014150:Antipsychotic Agents / Q000378:metabolism; D001665:Binding Sites; D001667:Binding, Competitive; D002090:Butyrophenones / Q000378:metabolism*; D002540:Cerebral Cortex / Q000378:metabolism; D003342:Corpus Striatum / Q000378:metabolism; D007457:Iodine Radioisotopes; D007553:Isotope Labeling; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000378:metabolism*; D013134:Spiperone / Q000031:analogs & derivatives / Q000378:metabolism*
chemical_list: D014150:Antipsychotic Agents; D002090:Butyrophenones; D007457:Iodine Radioisotopes; D011954:Receptors, Dopamine; D013134:Spiperone; C042868:4-iodospiperone