ON and OFF SACs receive distinct synaptic inputs. Schematic drawing of synaptic wiring in ON and OFF SACs (green cells) in the adult mouse retina. ON and OFF SACs both receive nicotinic receptor-mediated GABAergic inputs (blue) and only ON SACs receive additional muscarinic receptor-mediated GABAergic inputs (blue). These cholinergic receptors presumably exist in non-spiking amacrine cells other than SACs (cells surrounded by dotted lines). OFF SACs, but not ON SACs, have P2X₂ purinoceptors and respond to ATP (yellow) (Kaneda et al., 2008). ATP also activates P2X purinoceptors on amacrine cells (OFF SACs are a likely candidate) and increases GABAergic inputs (light blue) to OFF SACs. ON SACs selectively receive glycinergic inputs (green), presumably from narrow-field amacrine cells (Ishii and Kaneda, 2014). Canonical glutamatergic inputs (red) from bipolar cells (BC) are also shown. This glutamatergic circuit drives GABAergic inputs (light blue) to both ON and OFF SACs from neighboring amacrine cells (Ishii and Kaneda, 2014). Glu, glutamate; Gly, glycine; BC, bipolar cell; AC, amacrine cell; nAChR, nicotinic acetylcholine receptor; mAChR, muscarinic acetylcholine receptor.