Striatal glutamatergic hyperactivity in Parkinson's disease.

Glutamatergic hyperactivity in the nucleus striatum, the main basal ganglia input, has been involved in the progression of Parkinson's disease (PD) and the onset of L-Dopa-induced dyskinesias (LIDs). Abnormalities in the spiny projection neurons excitability and firing, and in the overactivity of glutamate transmission found in animal models of PD, pointed to the synaptic dysfunctions as a primary target to counteract alterations before overt neurodegeneration, conferring a key role to striatal glutamatergic transmission in the early phases of the disease. The present paper provides an overview of the evidence that glutamatergic overactivity is a critical mechanism underlying different PD-associated striatal alterations in early and advanced symptomatic stages of the disease. These aberrant changes, under L-Dopa therapy, lead to a more complex synaptopathy that involves other neurotransmitter systems and persistent modifications to generate LIDs. The review discusses the main changes in glutamatergic functions found in PD preclinical models and clinical studies and an update of the current pharmacological strategies to modulate the glutamatergic systems at the pre- and postsynaptic levels will be provided.