RGCs intracellularly injected with Lucifer yellow. A, B, Micrograph in A was taken with an infrared interferometric phase microscope and the retinal layers can be seen. Shown are representative Lucifer yellow-filled OFF-type (A, right) and ON-type (B, right) RGCs that possess dendrite arborizations in the proximal (a) and distal (b) parts of the IPL, respectively. Scale bar, 10 μm. C, D, Bar charts showing that 8-OH-DPAT remarkably enhanced the frequency (C) and the amplitude (D) of GABAergic mIPSCs. Note the significant differences in the frequency but not the amplitude of GABAergic mIPSCs between ON- and OFF-type RGCs. White columns: ON-type RGCs; Gray columns: OFF-type RGCs. ***p < 0.001 for the results of paired t tests between ON- and OFF-type RGCs before and after drug administration. ###p < 0.001 for an independent-samples t test with ON-type RGCs and OFF-type RGCs.