The monoamine oxidase inhibitors clorgyline and L-deprenyl also affect the uptake of dopamine, noradrenaline and serotonin by rat brain synaptosomal preparations

Clorgyline and l-deprenyl are, respectively, specific type A and type B monoamine oxidase (MAO) inhibitors. We investigated the effects of these two drugs as differential inhibitors of synaptosomal amine uptake and determined how far these effects might be predicted from their properties as specific MAO-A and MAO-B inhibitors. The rank order of inhibition of uptake by clorgyline was found to be: serotonin (ic₅₀ = 10 μM) dopamine (ic₅₀ = 56 μM) noradrenaline (ic₅₀ = 66 μM). The rank order of inhibition of uptake by l-deprenyl was: noradrenaline (ic₅₀ = 26 μM) serotonin (ic₅₀ = 460 μM) dopamine (ic₅₀ = 530 μM). The observation that clorgyline is a more specific inhibitor of the uptake of serotonin (a type A MAO substrate) is consistent with its activity as a type A MAO inhibitor. Paradoxically, L-deprenyl, though a type B MAO inhibitor, is fairly effective at inhibiting the uptake of noradrenaline (a type A MAO substrate).