Determination of dopamine D-4 receptor density in rat striatum using PB12 as a probe

N-[2-[4-(4-Chlorophenyl)piperazin-1-yl]ethyl]-3-tnethoxybenzamide (PB12), a potent and selective dopamine D-4 receptor ligand, was used as a probe for the direct determination of the dopamine D4 receptor density in rat striat um as an alternative to the subtraction method. The experiment was performe d using [H-3]spiroperidol to label D-2, D-3 and D-4 receptors and PB12 to d etermine directly dopamine D-4 receptor specific binding. The determined B- max value was 82 fmol/mg protein. The contribution of the dopamine D4 recep tor to the overall population of D-2-like receptors was 63%; however, this value cannot be considered reliable because of the observed difference in t he kinetic profiles of D-2, D-3 and D-4 receptors. (C) 2001 Elsevier Scienc e B.V. All rights reserved.