Continuous Dopaminergic Stimulation in Parkinson’s Disease—What Have We Learned from Positron-emission Tomography?

Abstract

Oral levodopa remains the most effective symptomatic drug for Dopamine-replacement Treatment and Pre-synaptic Dopaminergic FunctionThe COMT inhibitors entacapone and tolcapone increase levodopa bioavailability in the plasma and increase its transport into the brain by AbstractThe hypothesis that pulsatile stimulation of striatal dopamine receptors in Parkinson's disease (PD) induces molecular and physiologic changes in basal ganglia neurons and may contribute to the development of motor complications has led to the design of therapeutic strategies that provide more continuous dopaminergic stimulation. Newer agents and drug-delivery systems such as slow-release preparations, catechol-O-methyltransferase, and monoamine oxidase inhibitor agents, apomorphine, and Duodopa™ infusions represent a significant step towards less pulsatile dopaminergic administration. However, their efficacy in providing steady brain levels of dopaminergic stimulation in the short and longer term has not yet been proved in patients. This article briefly reviews and discusses the findings of published positron emission tomography (PET) studies that support or oppose the value of continuous dopaminergic stimulation in PD. The potential future value of PET for proof of mechanism in this area is also debated.