Uptake of (-) 3H-norepinephrine by storage vesicles prepared from whole rat brain: properties of the uptake system and its inhibition by drugs.

Neurotransmitter storage vesicles were isolated from rat brain by differential centrifugation and the uptake of (?) ³H-norepinephrine was determined $\text{in vitro}$. Uptake showed a marked temperature dependence, an absolute requirement for ATP-Mg²⁺, and was inhibited $\text{in vitro}$ by reserpine. Uptake was linear for 5 min at 30°, but not at 37°. The uptake was saturable and displayed a single Km value of 4 × 10^?7 M. Other phenylamines and indoleamines displayed competitive inhibition of norepinephrine uptake; the affinities followed the rank order: reserpine>harmaline>serotonin>epinephrine> dopamine>norepinephrine>metaraminol. Uptake was reduced in vesicles isolated from rats treated intracisternally with 6-hydroxydopamine but not from rats treated with 5,6-dihydroxytryptamine, suggesting that most of the uptake occurs in catecholaminergic, and not serotonergic, vesicles. This method provides a ready characterization of pharmacologic effects on rat brain storage vesicle properties, as demonstrated by the prompt and complete inhibition of uptake $\text{in vitro}$ after administration of reserpine $\text{in vivo}$.