Abstract
Purpose: :
In the mature rabbit retina, dendrites of the direction selective ganglion cells (DSGCs) and processes of the starburst amacrine cells (SACs) cofasciculate in the inner plexiform layer. Such cofasciculation pattern has been shown to play an important role in generating the direction selectivity of DSGCs. Consequently, it is possible that developing DSGCs remodel their dendrites following the early matured SAC processes during development. This study was aimed to characterize the temporal dynamics of dendritic relationship between DSGCs (including both monostratified ON and bistratified ON-OFF types) and SACs in the developing rabbit retina.
Methods: :
The retinas of New Zealand White rabbits from various postnatal stages were used in this study. The somata of potential DSGCs under DAPI staining were targeted for Neurobiotin injection. The processes of SACs were subsequently visualized by immunocytochemistry using an antibody against the vesicular acetylcholine transporters (VAChT). A series of z-stack confocal images of high magnification were acquired, and the degrees of costratification and cofasciculation were quantified using MetaMorph.
Results: :
We found that the dendrites of DSGCs and the processes of SACs were highly costratified and cofasciculated right after birth in the rabbit retina. In both ON and ON-OFF types of DSGCs, the degrees of co-fasciculation with SACs remained in the same level throughout the first two postnatal weeks.
Conclusions: :
Our results indicate that DSGC dendrites and SAC processes are already highly cofasciculated in an adult-like manner after birth. This is contrary to the assumption that rapid and extensive dendritic remodeling occurs during the early postnatal period. Thus, the early maturation of the DSGC-SAC cofasciculation pattern suggests that the dendritic connection necessary for generating direction selectivity is well developed before birth, much earlier than recording of direction selective responses of DSGCs at eye-opening (P10-11).
Keywords: development • amacrine cells • ganglion cells