Abstract
Purpose: :
Although it has been reported that the ON–OFF direction–selective ganglion cells (DSGCs) showed directional selective light responses around eye opening in the rabbit retina (Masland, 1977; Zhou and Lee, 2005), the developmental mechanisms underlying postnatal maturation of the DSGC circuitry is not clear. In light of recent findings that light deprivation alters the maturation of synaptic pathway in the mouse retina, we examined if visual experience is required for the maturation of DSGCs in the rabbit retina.
Methods: :
The DSGCs from whole mount retinas of New Zealand White rabbits raised in normal light–dark cycle and in the dark room were recorded extracellularlly at various postnatal stages. Receptive field properties, such as direction selectivity, velocity tuning, static surround inhibition, motion surround inhibition, and motion contrast were carefully characterized and compared. Recorded cells were subsequently injected with Neurobiotin for morphological identification and examining the pattern of trace coupling.
Results: :
We found that the DSGCs showed directional selective light responses around eye opening in both normal–reared and dark–reared rabbit retinas. The velocity tuning curves of DSGCs were narrower in P10–14 than in P22–adult, but no significant difference between normal and dark reared rabbits. Although surround inhibition were present in both normal and dark reared animals, the motion induced surround inhibition was stronger in dark–reared rabbits than in normal reared rabbits. Moreover, motion contrast of DSGCs was less well developed in dark–reared rabbits than in normal reared rabbits. Finally, the DSGCs showed similar dendritic morphologies and tracer coupling patterns in both normal and dark reared rabbits.
Conclusions: :
Visual experience is not critical for the maturation of classical receptive field properties of DSGCs, such as direction selectivity and velocity tuning. However, dark reared animals showed different surround inhibition mediated by amacrine cells in the inner retina.
Keywords: ganglion cells • development • receptive fields