GRIN2B and Huntington disease: In addition, there was a decrease in the NR2A/NR2B ratio in the striatum of WT mice, inducing a pro-excitotoxic effect, whereas the NR2A/NR2B ratio was increased in HD mice (R6/2), and thus the NMDA receptors provided an anti-excitotoxic effect (Ferrante et al., 2010).