Comparison of [ 3H]YM-09151-2 with [ 3H]spiperone and [ 3H]raclopride for dopamine D-2 receptor binding to rat striatum

The K d value of [ 3H]YM-09151-2, a potent and highly selective dopamine D-2 antagonist, for binding to rat striatum was about 20 pM (half of that for [ 3H]spiperone and one-fiftieth of that for [ 3H]raclopride). The B max of [ 3H]YM-09151-2 binding was about 30% higher than that of [ 3H]raclopride or [ 3]spiperone. The ratio (about 3%) of non-specific to specific binding of [ 3H]YM-09151-2 was smaller than that of [ 3H]spiperone and [ 3H]raclopride. The Hill coefficient values of dopamine D-2 antagonists, SCH23390, mianserin and phentolamine for the inhibition of binding of [ 3H]YM-09151-2 were near 1.0, and their K i values with [ 3H]YM-09151-2 were consistent with those for inhibiting [ 3H]raclopride and [ 3H]spiperone binding to D-2 receptors. Thus, [ 3H]YM-09151-2 may be the most suitable ligand for the labelling of dopamine D-2 receptors in the brain.