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H. Chen, N. Tian; Effect of Glutamate Receptor-Mediated Synaptic Activity on the Maturation of Mouse Retinal Ganglion Cell Directional Selectivity. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1414.
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© ARVO (1962-2015); The Authors (2016-present)
Our previous study showed that glutamate receptor (GluR)-mediated synaptic activity of mouse retinal ganglion cells (RGCs) was significantly reduced in T-cell receptor (CD3ζ) mutants and this reduction of GluR-mediated synaptic activity was accompanied by an impairment of activity-dependent RGC dendritic elimination. The goal of this study is to determine whether the development of directional selectivity of RGCs is affected with this impaired GluR-mediated synaptic activity and activity-dependent RGC dendritic elimination.
Multielectrode array (MEA) was used to record the action potentials of mouse RGCs evoked by moving bar stimuli. A white rectangular bar, which moves upon black background and perpendicularly to its long axis in 12 directions at 30 degree intervals, was used to evoke RGC light responses. The directional selectivity index (DSI) was calculated for both the leading and trailing edge (ON and OFF) responses, respectively.
Instead of selectively study morphologically or functionally identified directional selective RGCs (DSGCs), we examined the DSIs of all randomly recorded cells (in total of 1143 cells) from ganglion cell layer (GCL) of retina of young (P15) and adult (P33) wild type (WT) and CD3ζ-/- mice. In young (P15) WT mice, 14% of RGCs have DSI greater than 0.33 and most of them (94%) are ON-OFF RGCs and 6% are ON cells. At P33, 36% of RGCs have DSI greater than 0.33, in which 66% are ON-OFF RGCs and 34% are ON cells. Consistently, the average DSI of WT mouse RGCs increased significantly from P15 to P33 for both ON RGCs (200%), ON responses (165%) and OFF responses (145%) of ON-OFF RGCs. In P15 CD3ζ-/- mice, the relative population of RGCs with DSI greater than 0.33 (10%) and the average DSI are similar to that of age-matched WT controls. However, only 17% of RGCs have DSI greater than 0.33 in P33 CD3ζ-/- mice (in comparison with 36% of age-matched WT control) and the average DSIs of CD3ζ-/- mice at P33 are only 67-75% of the values of age-matched WT controls.
In contrast to recent publications, our results strongly suggest a developmental increase of directional selectivity of RGCs after eye opening. This developmental increase of DSI was reduced in CD3ζ-/- mice, indicating that GluR-mediated synaptic activity play an important role in the maturation of synaptic circuitry of DSGCs.
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