The excitatory amino acid L-glutamate is a major transmitter in the vertebrate central nervous system. We have shown that both ionotropic glutamate receptors ( NMDA or AMPA type) and metabotropic glutamate (mGlu) receptors are involved in visual responses and processing under different stimulus conditions (Binns & Salt, 1994; Cirone & Salt, 2001; Neale & Salt 2006) in the superior colliculus. Furthermore NMDA receptor and mGlu receptor function appear to change during development (Binns et. al. 1999; Lacey et.al., 2005).
Given these previous findings, we have begun to investigate how the role and function of these receptors may change during retinal degeneration and/or lesion, and again it appears that there are important changes in the function of NMDA receptors and mGlu receptors (Turner et.al. 2005; Pothecary et.al. 2005). This is important as it will reveal how the central visual system reacts to retinal degeneration and may open up new therapeutic avenues for the treatment of retinal degenerative diseases.
Recently we have shown that in experimental glaucoma, following degeneration of retinal ganglion cells (RGCs), there are functional changes that occur in the central visual targets for RGCs (Georgiou et.al., 2010). In particular, we have seen that there is an increase in the contribution of NMDA receptors to synaptic transmission in the superior colliculus, and that these changes occur at a relatively late stage after the main phase of apoptotic RGC loss. This suggests that early therapeutic intervention in glaucoma may be important to prevent CNS changes, and that there may be a potential ability for central areas to show plasticity following the loss of retinal input, and this may aid in the design of future treatments for limiting visual loss in glaucoma.
This page was written by Tom Salt, and is part of the Neurotransmitters in Sensory Systems Home Page.
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