DOPA is probably an endogenous transmitter and/or modulator in CNS (Prog Neurobiol 49: 415-454, 1996). It remains to be clarified whether there exist specific receptors for DOPA. As DOPA shows a glutamate-like excitatory action, we studied effects of DOPA-related agents on specific binding of glutamate receptor ligands in rat brain membrane preparations. DOPA inhibited binding of [ 3 H]-AMPA with low affinity (IC 5 0 =468 μM). The inhibition was not modified by 200 μM ascorbic acid. DOPA did not inhibit binding of [ 3 H]-KA, -DCKA, -CGP 39653 and -MK-801. DOPA methyl ester, a competitive antagonist for DOPA, and other ester compounds such as cyclohexyl ester, cyclopentyl ester and cyclopentyldimethyl ester, did not affect binding of [ 3 H]-AMPA, -KA, -DCKA and -CGP39653. These ester compounds inhibited binding of [ 3 H]-MK-801 with IC 5 0 0.2-1 mM. A recognition site for pM to μM DOPA itself reported thus appears to differ from AMPA, KA and NMDA receptors.