PHARMACOLOGY OF DOPAMINE D-3 RECEPTORS IN THE ISLANDS OF CALLEJA OF THE RAT USING QUANTITATIVE RECEPTOR AUTORADIOGRAPHY

The pharmacological properties of [H-3]7-hydroxy-N,N-di-n-propyl-2-ami notetralin ([H-3]7-OH-DPAT) binding sites in the islands of Calleja of the rat were studied using quantitative receptor autoradiography. The K-D and the B-max values of [H-3]7-OH-DPAT binding were about 1.6 nM and 100 fmol/mg protein, respectively. The rank order of potency was R (-)-propylnorapomorphine > 7-OH-DPAT approximate to haloperidol > racl opride > dopamine > remoxipride. Remoxipride injected in vivo (0.03-10 0 mu mol/kg i.p., 1 h before decapitation) did not inhibit subsequent [H-3]7-OH-DPAT binding. These results indicate that the pharmacologica l profile of dopamine D-3 receptors in the islands of Calleja of the r at resembles that obtained from cell lines or membrane preparations.