Brain sigma receptors labelled by [H-3]nemonapride

Binding of [H-3]nemonapride and [H-3]raclopride was examined in the brain areas of three species (rat, cow and human). The results indicated that [H-3]nemonapride binding is inhibited by selective a receptor ligands in frontal cortex, striatum and cerebellum. Only the striatum showed significant dopaminergic sites as defined by sulpiride. Use of the subtraction method of [H-3]nemonapride minus [H-3]raclopride binding as a measure of D-4 dopamine receptor binding may, therefore, also include a sigma receptor component.