Abstract: The P2X4 receptor belongs to the P2X receptor family of trimeric ligand-gated ion channels and was the first member of this family for which a crystal structure was obtained (Kawate et al., 2009). This structure confirmed the trimeric stoichiometry of P2X receptors and subsequent studies from the same group revealed the orthosteric binding site of the natural ligand adenosine 5′-triphosphate (ATP) in a cleft between each adjacent subunit (Hattori and Gouaux, 2012). Now synonymous with structural descriptions of P2X receptors, these original studies described the structure of each P2X4 receptor subunit as that resembling a dolphin, with the two transmembrane domains representing the fluke and the extracellular loop representing the upper body, including the head, dorsal fin, and left and right flippers. Along with subsequent structures of other P2X receptor members, obtained by either X-ray crystallography or cryo-electron microscopy, these studies have helped to further elucidate the agonist binding sites and conformational states during activation, as well as orthosteric and allosteric binding sites of P2X receptors (Mansoor, 2022). Transfer of this knowledge to the design of novel P2X4 receptor antagonists remains scant, with most antagonists described to date arising from the screening of chemical libraries and none advancing to clinical trials beyond NC-2600 (Inoue, 2021). Nevertheless, given the roles of the P2X4 receptor within the nervous system, this receptor remains an attractive therapeutic target in the treatment of a range of neurological disorders including pain (Sophocleous et al., 2022). In this regard, the screening of chemical libraries identified the anti-depressants, duloxetine and paroxetine as P2X4 receptor antagonists. This suggests that the historical use of such drugs to alleviate pain in people may have been, at least in part, due to P2X4 receptor inhibition and may warrant future trials for their potential use in humans to safely inhibit P2X4 receptor activity (Kohno and Tsuda, 2021).