Changing coupling pattern of The ON-OFF direction-selective ganglion cells in early postnatal mouse retina

In the adult rabbit and mouse retina, about 30% of the ON-OFF direction selective ganglion cells (DSGCs) are coupled via gap junctions. In early postnatal rabbit retinas, a greater proportion of morphological ON-OFF DSGCs shows coupling with a larger number of nearby somas. It is not clear whether the coupled ON-OFF DSGCs belong to the same subtype, or how coupling patterns change during development. In this study, we showed that in adult mouse retinas, all coupled ON-OFF DSGCs exhibited preferred directions (PDs) to superior, and this pattern emerged at postnatal day 15 (P15). At P13, the ON-OFF DSGCs with PDs to posterior were also coupled. Every ON-OFF DSGC in every subtype injected at P12 exhibited coupling. Therefore, a rapid decoupling process takes place in DSGCs around eye opening. Light deprivation delayed but did not halt the decoupling process. By using a transgenic mouse line in which green fluorescent protein (GFP) is selectively expressed in DSGCs with PDs to posterior and by performing in situ hybridization of cadherin-6, a marker for the DSGCs with PDs to superior and inferior, we showed that heterologous coupling existed between DSGCs with PDs to anterior and posterior till P12, but this heterologous coupling never spread to DSGCs positive for cadherin-6.