Estrogens, dopamine and dyskinesias.

Dear Sir: Current theories on the functioning of the extrapyramidal system suggest the existence of a balance between doparninergic and cholinergic influences. Tardive dyskinesia is usually observed after long-term administration of neuroleptics. During treatment of Parkinson's disease with L-DOPA, neurological manifestations similar to tardive dyskinesia can be observed. Agents decreasing dopaminergic activity, such as various antidopaminergic drugs and brain amine-depleting agents like tetrabenazine and reserpine, have been shown to have some beneficial effect on tardive dyskinesia, thus indicating the critical role of dopamine receptors in the pathogenesis of this neurological side effect (1,7,11-14). L-DOPAinduced dyskinesias can also be controlled by the administration of antidopaminergic drugs such as the neuroleptics (5,10).