Figure 1. Symmetric cholinergic and asymmetric GABAergic synaptic connectivity between SAC and DSGC.

A, Left-middle: Illustration of cell-attached recording from a DSGC showing the receptive field center (shaded in blue, mapped by a flashing a 80-μm×80-μm light spot in 13 locations), the preferred-null axis (indicated by arrows, identified by moving a 200-μm×600-μm light bar, shown in yellow, at 300 μm/s in 12 directions), and the spikes evoked by preferred and null movements (bottom traces). Right: Illustration of dual whole-cell recording from a DSGC and an overlapping SAC from the null direction. B, Upper: Photomicrographs of Lucifer yellow-filled SAC and DSGC pairs taken at the end of dual recordings, showing SACs located on the preferred (left), null (middle), and intermediate (right) side of the DSGC (scale bar, 50 μm). Lower: Synaptic transmission from SACs to DSGCs, showing spatially symmetric inward postsynaptic currents at -70 mV (~E_Cl) and spatially asymmetric outward currents at 0 mV (~E_Cat) in responses to step depolarization of SACs in 10 mV amplitude increments from a holding potential of -70 mV, in the presence of 40 μM CNQX. C, Complete blockade of the outward postsynaptic currents by SR95531 (50 μM) and of the inward postsynaptic currents by hexamethonium (HEX, 200 μM). D, HEX (200 μM) did not block the evoked outward postsynaptic current at 0 mV, neither did SR95531 (50 μM) block the evoked inward postsynaptic current at -70 mV. E, CNQX (40 μM) blocked the majority of spontaneous excitatory postysynaptic currents in the DSGC, with no effect on the evoked inward or outward current inputs from the SAC. Statistical summary of the maximum (F, G) and first-detectable (H, I) amplitude of the inward (cholinergic) and outward (GABAergic) postsynaptic currents evoked by preferred-, null-, and intermediate side SACs under dual patch-clamp recording. Error bars: s.e.m.