P2RX7 and Huntington disease: At the moment, the only study is published by Diaz and collaborators, who by using two distinct mouse models for HD, Tet/HD94 and R6/1 demonstrated that P2X7 receptor expression is increased in HD, and that the receptor channel possesses augmented Ca2+ permeability (Díaz-Hernández et al., 2009) (Figure 3).