P2RX3 and glaucoma: Moreover, different ligand–gated ion channels belonging to purinergic (e.g., the purinergic ionotropic receptor P2X3) and glutamatergic systems (e.g., the glutamate ionotropic receptor AMPA type subunit 1), might be predicted new pharmacological targets for glaucoma treatment, since no in vitro, in vivo, or clinical studies have been linked to these targets yet.