Preferential uptake of norepinephrine into dopaminergic terminals of a synaptosomal preparation from rat cerebral cortex.

In a synaptosomal preparation from male rat cerebral cortex only 34% of total norepinephrine (NE) uptake could be inhibited by nanomolar concentrations of desmethylimipramine (DMI) with an apparent IC50 value of 0.37 nM. The residual uptake was efficiently inhibited by micromolar concentrations of DMI (IC50 = 4.0 microM). In synaptosomes from the hypothalamus, 74% of total NE uptake could be blocked by DMI with an IC50 of 0.1 nM whereas in synaptosomes from the striatum the IC50 for DMI inhibition was 3.8 microM. It is concluded that in synaptosomes from rat cerebral cortex only 34%, and in synaptosomes from the hypothalamus 74% of total NE are taken up by noradrenergic nerve terminals whereas the residual NE uptake occurs in dopaminergic nerve endings.