Protection by Selegiline of Dopaminergic Neurons in Culture from Toxic Factors

PROTECTION BY SELEGILINE OF DOPAMINERGIC NEURONS IN CULTURE FROM TOXIC FACTORS 

In addition to MPTP, other endogenously produced neurotoxins, namely, the monoamine-derived 1,2,3,4-tetrahydroisoquinolines and 6,7-dihydroxy-l,2,3,4-tetrahydroisoquinolines, have been proposed as factors accelerating dopamine cell death. A-methylated isoquinolines were found to be oxidized by MAO, and hydroxyl radicals were found to be produced by this reaction. In addition, by incubation with the A-methylated isoquinolines, ATP was depleted from a dopaminergic cell model. Pretreatment of the cells with MAO inhibitors such as selegiline could, however, protect against ATP depletion. These results suggest that oxidation of neurotoxic isoquinolines is directly involved in the oxidative stress to induce the cell death of dopamine neurons. On the other hand, 1 -methyl-1,2,3,4-tetrahydroisoquinoline and 1 -methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquino- 

The cerebrospinal fluid of patients with Parkinson s disease contains substances that inhibit the growth and function of dopaminergic neurons in culture. Moreover, selegiline, an MAO-B inhibitor (0.125 to 0.250 iM) enhances the number of tyrosine hydroxylase (TH)-positive neurons, augments the high-affinity uptake of dopamine, and averts the neurotoxic effects of the cerebrospinal fluid of patients with Parkinson s disease on rat mesencephalic neurons in culture. 

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