High levels of extracellular glutamate are present in retina during neonatal development |
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Authors: | Michael F Haberecht Dianna A Redburn |
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Institution: | (1) Department of Ophthalmology and Visual Sciences, University of Texas-Houston, 6431 Fannin, 77030 Houston, Texas |
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Abstract: | The three major classes of neurons which comprise the primary visual pathway in retina are glutamatergic. These cells are
generated in two separate developmental stages, with one subclass of photoreceptors (cones) and ganglion cells generated before
birth; and the other subclass of photoreceptors (rods) and bipolar cells generated during the first week after birth. Gas
chromatography/mass spectroscopy analysis coupled with a new method for collecting small samples of extracellular fluids from
retina were used to determine the levels of endogenous glutamate present during differentiation and synaptogenesis of these
different cell types. As expected the total retinal content of glutamate increased during the postnatal period in synchrony
with the generation and maturation of glutamatergic cells. However, a significant proportion of the endogenous pool was found
extracellularly at birth. Intracellular glutamate is localized within cell bodies and growing processes of cones and ganglion
cells at this time but few glutamatergic synapses are present. The extracellular concentration of glutamate actually declined
during the most active period of synaptogenesis, reaching very low levels in the adult. The high concentrations of extracellular
glutamate in neonatal retina could play an important role in a variety of developmental events such as dendritic pruning,
programmed cell death and neurite sprouting.
Special issue dedicated to Dr. Kinya Kuriyama. |
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Keywords: | Glutamate retinal development glutamate release retina |
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