Abstract
Diagnosing Parkinson's disease (PD) before the clinical onset proves difficult because the hallmark PD symptoms do not manifest until more than 60% of dopamine neurons in the substantia nigra pars compacta have been lost. Here we show that, by evoking a transient dopamine release and subsequently measuring the levels of dopamine metabolites in the cerebrospinal fluid and plasma, a hypodopaminergic state can be revealed when less than 30% of dopamine neurons are lost in mouse PD models. These findings may lead to sensitive and practical screening and diagnostic tests for detecting early PD in the high-risk population.