Levodopa consumption reduces dopaminergic receptor responsiveness in Parkinson's disease
Vaamonde J., Luquin M.R., Obeso J.A.
In seven patients with Parkinson's disease with daily motor fluctuations, we found that the same subcutaneous apomorphine dose that improved motor function when given in the morning after a normal night without taking levodopa failed to turn patients on during afternoon and evening off periods, and on a different morning after receiving levodopa during the night.
No significant changes in levodopa or 3-O-methyldopa plasma levels that could explain these variations were detected. These findings suggest that increased daily levodopa consumption may reduce striatal responsiveness to dopaminergic stimulation.
CITATION Clin Neuropharmacol. 1989 Aug;12(4):271-84