Inhibition of 3H-noradrenaline accumulation by dopexamine hydrochloride in the isolated aorta of the rabbit.

The aim of the present work was to study the ability of dopexamine hydrochloride to interfere with the neuronal and extraneuronal uptake mechanisms by investigating the effect of dopexamine hydrochloride on 3H-noradrenaline accumulation by rabbit isolated aorta. Dopexamine hydrochloride (3 x 10(-9) - 10(-5) mol/l) reduced the accumulation of tritium by aorta incubated with 3H-noradrenaline (10(-8) mol/l). The effect of dopexamine was compared to cocaine, dopamine, dobutamine, ADTN [(+/-)-2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene], ouabain and isoprenaline. Dopexamine hydrochloride (3 x 10(-9)-10(-7) mol/l) caused the same degree of inhibition irrespective of whether corticosterone (4 x 10(-5) mol/l) was present or not. The order of inhibitory potency was: desipramine greater than dopexamine hydrochloride greater than dopamine greater than ADTN greater than or equal to cocaine greater than dobutamine greater than ouabain greater than isoprenaline. In the presence of desipramine (10(-6) mol/l), corticosterone (10(-6)-10(-4) mol/l), but not dopexamine hydrochloride (10(-6) - 10(-4) mol/l), reduced the 3H-accumulation. It is concluded that dopexamine hydrochloride is a potent inhibitor of uptake-1 in rabbit isolated aorta. Dopexamine hydrochloride has no affinity for the uptake-2 mechanism in this tissue.