The physiological function of kainate receptors (GluK1–GluK5) in the central nervous system is not fully understood yet. With the aim of developing potent and selective GluK1 ligands, we have synthesized a series of new thiophene-based GluK1 agonists (6a–c) and antagonists (7a–d). Pharmacological evaluation revealed that they are selective for the GluK1 subunit, with 7b being the most subtype-selective ligand reported to date (GluK1 vs ...