Compensatory responses to glaucoma pathology in the dorsolateral geniculate nucleus

Glaucoma disrupts the conveyance of retinal signals to visual regions of the brain such as the dorsolateral geniculate nucleus (dLGN) due to degeneration of retinal ganglion cells (RGCs) and their axons. Although plasticity during development allows altered visual experience to modulate dLGN synapses and excitability, evidence for experience-dependent dLGN plasticity in adults is limited. However, glaucoma might trigger compensatory plasticity in adult dLGN, thereby compensating for diminished RGC synaptic drive. Here, we tested this using aged (11-15 month-old) DBA/2J mice, which develop high intraocular pressure and glaucoma. In brain slice recordings, we found that diminished RGC inputs could drive robust action potential firing in dLGN relay neurons that was comparable to controls. This was accompanied by increased intrinsic excitability and decreased magnitude of sustained inhibitory currents from GABA spillover to extrasynaptic receptors. These results implicate multiple cellular and synaptic mechanisms that support signaling despite the diminished RGC inputs in glaucoma.