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X. Chen, F. S. Werblin; ON-Beta and ON-Parasol Retinal Ganglion Cells Share Similar but Complex Synaptic Inputs in Rabbit Retina. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4325.
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© ARVO (1962-2015); The Authors (2016-present)
To study and compare the spatial and temporal properties of the interactions between the excitatory and inhibitory synaptic inputs to ON-beta and ON-parasol ganglion cells, the two major types of ON-ganglion cells with small to mid-size receptive fields, that stratify near the middle of IPL.
Excitation and inhibition to ON-beta and ON-parasol cells in flat mount retina was measured by voltage-clamping at -60mV or 0mV. Cells were identified by different morphology and spatial-temporal activity patterns. Light discs and annuli were flashed to study the spatial properties of different excitatory and inhibitory inputs. Inhibitory blockers, strychnine and SR95531+TPMPA (ST) blocked glycinergic or GABAergic pathways. APB blocked ON activity.
1. Surprisingly, in the presence of all the inhibitory blockers plus APB, flashes within the dendritic field elicited OFF excitatory currents in both ON-beta and ON-parasol cells. The combination of any pair of drugs (strychnine, ST and APB) also uncovered this OFF excitatory current that was significantly weaker than with three blockers. 2. Both ON-beta and ON-parasol cells receive feedforward ON and OFF glycinergic inhibition to stimuli within the dendritic field. 3. ON-beta cells received ON and OFF feedforward GABAergic inhibition to stimuli within dendritic field. ON-parasol cells received ON and OFF feedforward GABAergic inhibitory inputs elicited over regions much broader than the dendritic area.
Although we designate them as ON cells, the ON-beta and ON-parasol cells receive OFF excitatory inputs to stimuli within the dendritic field, but the OFF excitatory input doesn’t generate spike output under normal conditions. Both cell types receive ON and OFF narrow glycinergic feedforward inhibitory inputs. Differences existed in GABAergic inhibitory inputs: GABAergic input to the ON-parasol is broader than that to the ON-beta cell. These results followed the general rules in retina: Inhibition carried by glycinergic amacrine cell was narrow, but GABAergic amacrine cells inhibition was either narrow or broad. It also suggests that narrow glycinergic, narrow GABAergic and broad GABAergic inhibitory inputs represent a fundamental set of inhibitory components in retina.
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