Abstract
Purpose: :
To determine the effects of laser-induced ocular hypertension (LIOH) on retinal ganglion cell (RGC) synapse number in the retina and dorsal lateral geniculate nucleus (dLGN) of CD-1 albino mice.
Methods: :
Elevated intraocular pressure (IOP) was induced unilaterally using laser photocoagulation of the limbal and episcleral veins of adult CD-1 mouse eyes. IOP was measured by rebound tonometry. Retinal sections were immunostained with both pre-synaptic (e.g. ribeye) and post-synaptic (e.g. PSD95) markers to quantify synapse number in the inner plexiform layer. Synapse number in the dLGN was quantified using immunohistochemistry with vGluT2, an RGC pre-synaptic marker.
Results: :
After laser-induced ocular hypertension, IOP elevations of the treated eye occurred within 6 hours and returned to baseline by 1 week. At early time points, there was loss of PSD95-positive puncta in the inner plexiform layer of the treated eye, but there was no difference in ribeye-positive puncta number or the number of Brn3a-positive RGCs in the ganglion cell layer. In the dLGN, there is loss of vGluT2-positive puncta in the contralateral dLGN, which fits our prediction given that the majority of retinogeniculate axons project to the contralateral dLGN.
Conclusions: :
RGC synapse loss occurs both in the inner plexiform layer of the retina and the contralateral dLGN in this laser-induced intraocular hypertension mouse model. The data supports further work focusing on RGC synapses as diagnostic and treatment targets.
Keywords: synapse • ganglion cells • thalamus/lateral geniculate nucleus