GRIN2B and Parkinson disease: Alterations in the ratio of GluN2B-containing NMDARs and GluN2A-containing NMDARs at synapses on MSNs correlate with dysfunctional motor behaviors, which has been thought to underlie striatum-related neurologic disorders such as Parkinson’s disease (PD) and Huntington’s disease (HD; Gardoni and Bellone, 2015).