NBQX reduces NMDAR EPSCs by blocking input from the rod pathway. A, CPPG-evoked EPSCs were reduced by NBQX (5 μm). B, The NBQX-sensitive component of the EPSC exhibited a J-shaped voltage dependence, indicating that it was mediated primarily by NMDARs. C, NBQX does not block NMDARs, as it did not affect responses in RGCs to exogenous NMDA (100 μm; Vhold = +40 mV). D, NBQX did not effect CPPG responses in RBCs, indicating that it did not act on mGluR6. E, NBQX blocked CPPG-evoked EPSCs in AII amacrine cells. F, NBQX strongly reduced CPPG responses in ON CBCs. G, As in F, but in a wild-type (WT) mouse ON CBC. H, NBQX did not affect CPPG responses in ON CBCs from Cx36−/− mice. I, NBQX reduced CPPG-evoked EPSCs in RGCs from WT mice. J, NBQX also reduced CPPG-evoked EPSCs in Cx36−/− mice, but to a lesser extent than in WT. K, Summarized effects of NBQX on CPPG-evoked responses in ON CBCs and RGCs. n values are indicated in parentheses.