Cellular and Synaptic Dysfunctions in Parkinson's Disease: Stepping Out of the Striatum

The basal ganglia (BG) are a collection of interconnected subcortical nuclei that participate in a great variety of functions, ranging from motor programming and execution to procedural learning, cognition, and emotions. This network is also the region primarily affected by the degeneration of midbrain dopaminergic neurons localized in the substantia nigra pars compacta (SNc). This degeneration causes cellular and synaptic dysfunctions in the BG network, which are responsible for the appearance of the motor symptoms of Parkinson's disease. Dopamine (DA) modulation and the consequences of its loss on the striatal microcircuit have been extensively studied, and because of the discrete nature of DA innervation of other BG nuclei, its action outside the striatum has been considered negligible. However, there is a growing body of evidence supporting functional extrastriatal DA modulation of both cellular excitability and synaptic transmission. In this review, the functional relevance of DA modulation outside the striatum in both normal and pathological conditions will be discussed.This research was funded by the French Agence Nationale de la Recherche (grants 08-JCJC-0087, 2014-CE13-0024-01 and 2015-CE37-0006), the Euroregion Aquitaine-Euskadi (Neurosciences grant number 9), the University of the Basque Country (LD joint doctoral grant), the Association France Parkinson (SNR-PARK grant), the Spanish Government (SAF2016-77758-R [AEI/FEDER, UE]), and the LABEX BRAIN ANR-10-LABX-43 grant (MC post-doctoral grant). The University of Bordeaux and the Centre National de la Recherche Scientifique provided infrastructure support