Abstract
Purpose: :
The ganglion cell type responsible for opponent blue-yellow color vision has been described in primate retina (Dacey and Lee 1994), but has been largely uninvestigated in non-primate mammals since blind recordings over 25 years ago, except for a recent study in guinea pig retina (Yin et al. 2009). We describe here several recordings coupled with intracellular staining in blue/green opponent ganglion cells in the rabbit retina.
Methods: :
Ganglion cells of the rabbit retina were visualized with acridine orange and recorded using the loose patch technique, then stained by electroporation with Neurobiotin. LEDs were used to present full-field blue and green stimuli singly and in combinations including isolating cone stimuli.
Results: :
At least two types of opponent B/G ganglion cell can be found in rabbit retina. A B-ON/G-OFF ganglion cell was the most commonly encountered. Similarly to primate (Crook et al. 2011), addition of HEPES buffer to the perfusate abolished opponency, resulting in ON responses to either B and G stimulation. APB abolished all firing in this cell type. This ganglion cell was monostratified in a narrow band at about 75% depth in the IPL, just above the rod bipolars, where blue cone bipolars are expected to ramify. Coupling to amacrine cells was variable and possibly bimodal, perhaps suggesting that there were two subtypes, one completely uncoupled and one coupled to amacrine cells.More rarely, we encountered B-OFF/G-ON ganglion cells. These also ramified in sublamina b and had wavy dendrites that were more broadly stratified than the other type. Firing was also abolished by APB, suggesting an inversion of the ON pathway. Again, opponency was lost with addition of HEPES to the buffer.
Conclusions: :
At least two types of B/G ganglion cell exist in the rabbit retina. Both appear to emanate from the ON pathway. The conversion of the responses of these cells to non-opponency with HEPES suggests that B/G color opponency arises from horizontal cell contributions to the receptive field.
Keywords: ganglion cells • color vision • horizontal cells