(A) Schematic diagram shows transgenes involved in Gabra2 conditional KO mice. The KO mice carry homozygous floxed Gabra2 allele to replace the endogenous Gabra2 gene for Cre-dependent excision (acronym: Gabra2flox/flox), and Chat-IRES-Cre (C). The floxed tdTomato (T) and a Drd4-GFP transgene to label pDSGCs (D) were also included when SACs or pDSGCs were targeted for electrophysiological recordings. (B) Example traces of spontaneous IPSCs (sIPSCs) in On SACs from control (CT) and Gabra2 KO (Gabra2flox/flox CT) mice. (C) Summary bar graph of sIPSC frequency in control and KO groups. Control: 0.28 ± 0.07 Hz, n = 18 cells, five mice; KO: 0.02 ± 0.04 Hz, n = 16 cells, four mice. ***p<0.0005. (D) Example evoked IPSC traces from reciprocal On SAC-SAC pairs in Control and Gabra2 KO mice. (E) Voltage clamp traces from null-side and preferred-side SAC-DSGC pairs in control (CTD) and KO (Gabra2flox/floxCTD) mice showing cholinergic EPSCs (red inward) and GABAergic IPSCs (black outward) evoked in pDSGCs by depolarizing SACs. Schematic on left shows soma locations of the null and preferred side pairs. Black arrows indicate the pDSGC’s preferred direction. (F) Summary bar graphs of IPSC and EPSC peak amplitudes in pDSGCs evoked by null (N) and preferred (P) side SACs in control and KO groups. IPSC: Control – N: 247.9 ± 40.8 pA, n = 14 cells, seven mice; Control – P: 43.0 ± 30.1 pA, n = 14 cells, seven mice; KO – N: 233.8 ± 43.7 pA, n = 7 cells, four mice; KO – P: 41.3 ± 10.0 pA, n = 8 cells, five mice, **p<0.005, ***p<0.0005; EPSC: Control – N: 165.2 ± 40.4 pA, n = 14 cells, seven mice; Control – P: 96.6 ± 32.2 pA, n = 14 cells, seven mice; KO – N: 127.4 ± 20.4 pA, n = 7 cells, four mice; KO – P: 175.0 ± 31.9 pA, n = 8 cells, five mice, one way ANOVA p=0.07. (G) Summary bar graphs of EPSC amplitudes and total charger transfer in pDSGCs evoked by onset and offset of a bright spot in control and KO mice. Peak amplitude: Control On, 224.6 ± 26.7 pA; KO On, 242.7 ± 19.5 pA, p=0.58; Control Off, 216.5 ± 23.8 pA; KO Off, 242.4 ± 25.9 pA, p=0.46. Charge Transfer: Control On, 42.3 ± 5.6 pA∙s; KO On, 52.2 ± 5.9 pA∙s, p=0.22; Control Off, 48.7 ± 4.2 pA∙s; KO Off, 49.4 ± 4.9 pA∙s, p=0.92. Control, n = 21 cells, nine mice; KO, n = 30 cells, 11 mice.