A-381393 potently bound to the membrane from cells expressing recombinant human dopamine D4.4 receptor (Ki=1.5 nM), which was 20-fold higher than that of clozapine (Ki=30.4 nM). A-381393 exhibited highly selective binding for the dopamine D4.4 receptor (>2700-fold) when compared to D1, D2, D3, and D5 dopamine receptors. A-381393 potently inhibited the functional activity of agonist-induced GTP-gamma-S binding assay and 1 microM dopamine-induced-Ca2+ flux in human dopamine D4.4 receptor-expressing cells, but not in human dopamine D2L or D3 receptor cells [1]. A-381393 blocked both c-Fos expression and ERK1/2 phosphorylation produced by PD168077. Treatment with A-381393 alone significantly reduced the amount of Fos immunoreactivity as compared to basal expression observed in vehicle-treated controls [2].