Abstract
Purpose:
Waves of activity sweep across the early postnatal retina and contribute to the refinement of retinofugal projections. These retinal waves occur before rod and cone circuits can drive the inner retina, but after melanopsin ganglion cells are fully competent. Previous research has demonstrated that light, through the activation of melanopsin ganglion cells, increases the duration of wave-associated bursts of non-melanopsin ganglion cells. Here, we investigate the effects of light on additional wave-associated ganglion cell bursting properties.
Methods:
We recorded wave activity from retinal ganglion cells (RGCs) in early wildtype postnatal mouse retinas (P4-7) using multielectrode arrays. Recordings were made in the dark, light, and then again in the dark after a period of dark adaptation. Electrodes with light evoked spiking were presumed to be sampling spikes from melanopsin ganglion cells and were removed from data analysis.
Results:
As previously reported, we found that light significantly increased the duration of retinal ganglion cell wave-associated bursts. In addition, we found light increased ganglion cell background firing rates, while significantly reducing the in-burst peak firing rate, and the average number of spikes within bursts. There was no significant change in the mean inter-burst interval.
Conclusions:
Light modulates the dynamics of retinal waves in early postnatal retinal development. Initial reports of melanopsin ganglion cell - mediated effects on wave activity suggested only changes in the duration of wave-associated bursts. Here we report light alters a number of critical wave-burst metrics, suggesting the effects of light-evoked melanopsin ganglion cell activity on retinal waves may be more substantial than initially thought.