Abstract
Purpose: :
How do retinal ganglion cells functionally segregate in the developing eye? Previous studies have shown that adult retinal ganglion cells can be classified not only by dendritic morphology and stratification within the inner plexiform layer, but by characteristic differences in their responses to light stimuli (Volgyi et al, 2004). We investigated whether light-evoked responses of ganglion cells in 14 day-old mice can be classified as readily as in adults.
Methods: :
Extracellular action potentials were recorded simultaneously from 30-90 retinal ganglion cells in the in vitro retina of 14 day old wild type (wt) and rd1 mice, using a multielectrode array. Spontaneous activity was monitored and full field light flashes were presented over a range of illuminance values. Light-evoked responses were displayed as peri-stimulus time histograms for each cell to identify ON and OFF response phases. Intensity-response curves were plotted for each of these phases across the range of stimulus intensities.
Results: :
At this age, ganglion cells are not as readily classified according to these intensity-response curves in the adult retina in either the wt and rd1 retinas. This parallels the observation of Tian that cells have not completely stratified into their respective layers, finding 56% ON/OFF cells, 24% ON cells, and 20% OFF cells (total n=115). Intensity-response curves show that ON cells and OFF cells segregate into two groups, as determined by the intensity at which 10% of maximum cellular response is attained, while Volgyi et al showed mature ON and OFF ganglion cells segregated into three and four groups, respectively.
Conclusions: :
We suggest that developing retinal ganglion cells span a functional spectrum, but have not completely segregated into distinct, mature groups. The
Keywords: ganglion cells • development • electrophysiology: non-clinical