EEDQ, a tool for ex vivo measurement of occupancy of D-1 and D-2 dopamine receptors.

EEDQ (N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline) inactivates dopamine (DA) D-1 and D-2 receptors, measured by ex vivo [3H]SCH 23390 and [3H]spiperone binding in striatal homogenates. SCH 23390 (D-1 antagonist) and SK&F 38393 (D-1 agonist) protect against inactivation of D-1 receptors (ED50 values 0.075 and 53 mumol/kg, respectively). Raclopride (D-2 antagonist) and quinpirole (D-2 agonist) protect against inactivation of D-2 receptors (ED50 values 0.48 and 7.1 mumol/kg, respectively). The potencies correspond closely to those obtained by in vivo binding experiments using radioligands.