A, application of 5 μm CGP55845 alone did not alter EPSCs compared to control. B, however, 100 μm PTX enhanced the light responses (light grey trace) and 5 μm CGP55845 in the presence of PTX reduced ON and OFF EPSCs (black trace). C, 5 μm CGP55845 in the presence of SR95531 produced a large suppression of the ON response and a small reduction in the OFF response. D, 100 μm TPMPA prolonged the light responses, particularly at light onset (light grey trace). But 5 μm CGP55845 in the presence of TPMPA (black trace) had a negligible effect on light-evoked EPSCs (n= 5). All of the indicated currents were recorded from a same ganglion cell.