Autoradiographic localization of extrastriatal D2-dopamine receptors in the human brain using [125I]epidepride

Epidepride is a benzamide with high affinity for central D2- and D3-dopamine receptors. The anatomical distribution of [125I]epidepride binding was examined by autoradiography, using postmortem human whole-hemisphere cryosections. The density of [125I]epidepride binding sites was high in caudate nucleus and putamen. [125I]epidepride also labeled receptors in extrastriatal region such as in the pallidum, some thalamic nuclei, the neocortex, and the substantia nigra. The neocortical binding was heterogeneously distributed. In most cortical regions, binding sites were located in superficial layers (I-II). However, in basal levels of the occipital cortex, [125I]epidepride binding was located in a deeper layer, probably corresponding to layer V. Competition studies indicated that most of the [125I]epidepride binding represented predominantly D2-dopamine receptors, in striatal as well as in extrastriatal regions. The presence of extrastriatal D2-dopamine receptor populations is of particular interest for research on schizophrenia and antipsychotic drug action.