Dendritic Pathology in Geniculate Neurons of the Brain Occurs Early in Glaucoma

Abstract

Abstract: : Objective: To determine whether dendrites of LGN neurons, responsible for integrating synaptic responses from retinal ganglion cells and visual cortex inputs, show pathological changes following experimental primate glaucoma. Methods: Six monkeys with chronic ocular hypertension and varying degrees of optic nerve fiber loss in the right eye (0%, 1%, 17%, 29%, 61%, 90%) and five normal control monkeys were studied. The dendrites of left LGN neurons were visualized with an antibody against microtubule–associated protein–2 (MAP–2), the major cytoplasmic structural protein restricted to dendrites. Results: MAP–2 positive dendrites of lateral geniculate neurons in layers 1,4, and 6 were distinctly disorganized, shorter, and fragmented compared to controls. These dendritic changes were present whether glaucomatous damage was early, moderate or advanced. Furthermore, the striking architectural changes were noted in LGNs with ocular hypertension without significant optic nerve fiber damage. Conclusions: Dendritic pathology of lateral geniculate neurons in the brain occurs early following elevated intraocular pressure. Alterations at these sites of synaptic integration may contribute to the earliest visual dysfunctions in glaucoma, and may be a target for therapeutic interventions prior to cell death.

Keywords: neuroprotection • pathology: experimental • thalamus/lateral geniculate nucleus