LBG20304 (compound 2s) is a ligand for the homologous GluK5 receptor ( IC 50 : 432 nM), more than 40-fold selective over the homologous GluK1-3 isoforms. Low doses of LBG20304 (<10 μM) have no agonist or antagonist functional response at heterologous GluK2/5 receptors, and at high doses (>10 μM), it exhibits low agonist activity in neuronal slices (rat).