1. Hernandez-Olmos V, et al. N-substituted phenoxazine and acridone derivatives: structure-activity relationships of potent P2X4 receptor antagonists. J Med Chem. 2012 Nov 26;55(22):9576-88. 2. Stokes L, et al. P2X4 Receptor Function in the Nervous System and Current Breakthroughs in Pharmacology.Front Pharmacol. 2017 May 23;8:291.