Single administration - 10 uM

Using [3H]U-86170, a dopamine receptor agonist, the drug affinities were determined at the high affinity agonist state of the dopamine hD21 receptor, and using [3H]raclopride, a dopamine receptor antagonist, in the presence of 600 mkM GTP the drug affinities were determined at the low affinity agonist state of the receptor. Using [ 3H]( +)-2-(N-propyl-N-2-thienylethylamino)-5-hydroxytetralin ([3H]N-0437) (0.6 mkM) in 50 mM Hepes, l0 mM MgSO 4, pH 7.4, an agonist at the dopamine hD4. 4 receptor, the drug affinities were determined at the high affinity agonist state of the hD4. 4 receptor, and using [3H]YM-09151-2, a dopamine hD4. 4 antagonist, in the presence of 600 mkM GTP the drug affinities were determined at the low affinity agonist state of the dopamine hD4. 4 receptor. Incubation was for l h at room temperature, samples were filtered, and counted. The non-specific binding determinant was 3 mkM pimozide.