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

The Kd 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 Bmax of [3H]YM-09151-2 binding was about 30% higher than that of [3H]raclopride or [3]spiperone. The ratio (bout 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 Ki 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.