Effect of MAO inhibitors on the uptake and metabolism of dopamine in rat and human brain.

Complex pharmacological effect of l-deprenyl cannot be explained by its MAO-B inhibitory action only. In contrast to other parent MAO inhibitors (J-512, J-516, LK-63, U-1424) l-, and d-deprenyl inhibit the hypothalamic noradrenaline and striatal dopamine (DA) reuptake without influencing the uptake of serotonin, both in rat and in human brain. Long-term treatment 19 x 0.25 mg/kg or 0.5 mg/kg, sc with l-deprenyl elicits 37 +/- 2.8 and 43 +/- 3.2% inhibition, respectively, of DA reuptake capacity in the rat striatal cell-free homogenate. To compare the potencies of deprenyl isomers on DA and DOPAC levels of rat striatum drugs were given 0.25, 2 and 8 mg/kg ip and their effects measured 4 and 48 h after treatment. DA content was increased only by 8 mg/kg d-deprenyl 4 h after its injection, but DOPAC level was decreased by both isomers. After 48 h, actions of d-deprenyl terminated but the effect of l-deprenyl was still present.