[3H]nemonapride binding in human caudate and putamen

The binding of [3H]nemonapride to human postmortem caudate and putamen tissue was autoradiographically investigated using several antipsychotic drugs. Saturation experiments revealed a single population of binding sites (dissociation constant (KD) 0.38 +/- 0.01 nM, and total binding capacity (BMAX) 55 fmol/TE). Prototypic dopamine (DA) receptors antagonists displaced [3H]nemonapride in a monophasic manner. The order of displacement potency was expected for DA D2-like receptors: spiperone > (+)butaclamol > or = chlorpromazine > (-)sulpiride > ketanserin. Displacement with serotonergic antagonists suggests that in human caudate and putamen tissue [3H]nemonapride may have a very low affinity serotonergic component. However, [3H]nemonapride displays a high affinity and selectivity for DA D2-like receptors and should make, it a preferred compound for tritium-based autoradiography.