ON THE MECHANISM OF THE NULLIFICATION OF CNS EFFECTS OF l‐DOPA BY PYRIDOXINE IN PARKINSONIAN PATIENTS1

Publisher Website
Google Scholar
Abstract
Administration of either Levodopa (l‐DOPA) or pyridoxine increased the concentration of dopamine in the basal ganglia of rats. However, administration of pyridoxine to rats pretreated with l‐DOPA for several days resulted in a reversal of the l‐DOPA‐induced elevation of dopamine. Pretreatment of rats with Ro 4‐4602 (an inhibitor of peripheral aromatic amino acid decarboxylases) enhanced the l‐DOPA‐induced rise in the CNS level of dopamine. This effect was also reduced substantially after the administration of pyridoxine. We interpret these results to indicate that the antagonistic effect of pyridoxine on the beneficial effects of l‐DOPA in the CNS is centrally mediated as a result of decreased formation of dopamine.