[Effect of reserpine on monoamine uptake by rat brain synaptosomes]

With regard to the inhibition of monoamine-uptake the concentration response curve of reserpine shows a biphasice turn. The first phase produces a maximum dopamin-uptake inhibition of 55% (EC50:8 X 10(-9) mol X 1(-1)) which is of a competitive manner only in the presence of a very low reserpine concentration (1 X 10(-9) mol X 1(-1)). Higher concentrations of reserpine inhibit the dopamine-uptake non competitively. This specific irreversible vesicular reserpine effect used therapeutically forms a plateau within a concentration rank from 10(-7) mol X 1(-1) to 10(-5) mol X 1(-1). A second mode of action of reserpine affects obviously the carrier mechanism located at the synaptosomal membrane (EC50: 5 X 10(-5) mol X 1(-1)). This second phase differs both from the first vesicular reserpine effect and from the synaptosomal action of tricyclic antidepressant drugs by its kinetic behavior (Km, Vmax).