[3H]-domperidone labels only a single population of receptors which convert from high to low affinity for dopamine in rat brain.

Dopamine recognized and competed for a single population of [3H]-domperidone-binding sites in rat striatum and olfactory tubercle when tested in the presence of sodium ions and guanine nucleotide [Gpp(NH)p]. In the absence of Na+ and Gpp(NH)p, however, dopamine recognized two components of [3H]-domperidone binding. Thus, [3H]-domperidone labelled only a single population of dopamine receptors (type D2) which fully converted from high to low affinity for dopamine. These results agree with those found previously using [3H]-spiperone and [3H]-YM-09151-2.