Excitatory and inhibitory neurotransmitter alterations with advancing age and injury in the mouse retina

Increasing age and elevated intraocular pressure (IOP) are the two major risk factors for glaucoma, the most common cause of irreversible blindness worldwide. Accumulating evidence is pointing to metabolic failure predisposing to neuronal loss with advancing age and IOP injury. Many neurotransmitters are synthesized from endogenous metabolites and are essential for correct cell to cell signaling along the visual pathways. We performed detailed, small molecule metabolomic profiling of the aging mouse retina and further explored the impact of IOP elevation at different ages. The resultant metabolomic profiles showed clear discrimination between young and middle-aged retinas and these changes are accentuated following eye pressure elevation. Alterations in glutamate and Gamma-aminobutyric acid (GABA) related metabolites were the most apparent changes with advancing age with further reductions in GABA and related pathways after IOP elevation. These changes were further confirmed using immunohistochemistry and patch-clamp electrophysiological recording experiments.