Pharmacological modifications of dopamine transmission do not influence the striatal in vivo binding of [H-3]mazindol or [H-3]cocaine in mice

We have considered the in vivo striatal binding of two ligands of the neuronal dopamine uptake complex: [H-3]cocaine and [H-3]mazindol. The [H-3]cocaine tracer dose labelled the dopamine uptake complex in striatum but not the noradrenaline complex in cerebellum. On the contrary, the [H-3]mazindol tracer dose induced a marked labelling of the noradrenaline uptake complex in cerebellum; its prevention by desipramine (5 mg/kg) increased simultaneously the cerebral bioavailability and thereby the striatal labelling of the dopamine transporter. In mice submitted to treatments modifying dopaminergic transmission either to decrease it (gammabutyrolactone, 750 mg/kg, i.p.) or to increase it (L-DOPA, 200 mg/kg, i.p., dexamphetamine, 4 mg/kg, s.c., or their combination), only dexamphetamine pretreatment significantly reduced [H-3]cocaine and [H-3]mazindol binding. Thus it appears that the level of dopamine transmission would not interfere with the in vivo quantification of striatal dopamine uptake sites assessed with either ligands.