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F. Germain, R. Blanco, P. De la Villa; Expression and Funcionality of Gaba and Glutamate Receptos in Axotomized Ganglion Cells of the Rabbit Retina . Invest. Ophthalmol. Vis. Sci. 2006;47(13):160.
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© ARVO (1962-2015); The Authors (2016-present)
To study expression and functional activity of GABA and Glutamate receptors in rabbit Retinal Ganglion Cells (RGCs) one month after optic nerve section. We have reported that one month after optic nerve section more than 90% of RGCs die. Surviving cells showed an increase in the dendritic length, spreading their processes out of the normal dendritic field, however, the functionality and possible connections with other cells are unknown.
New Zealand rabbits were used for all the experiments. Optic nerve section was performed by sectioning the right optic nerve completely, at 4 mm behind the eyeball. Undamaged left eyes were used as controls. For functional test of neurotransmitter receptor, RGCs were enzymatically dissociated from retinas of adult rabbits one month after optic nerve section. The ionic currents induced by the application of excitatory and inhibitory neurotransmitter agonist were recorded from isolated RGCs by using the whole cell patch–clamp technique. For immunohistochemistry, antibodies against glutamate receptor (Glut 6/7) and α1 subunit of the GABAA receptor were used. Standard optic immunofluorescence was performed on 15 µm sections of injured and not injured (left retinas) and the GABA and Glutamate receptors expression was compared.
One month after optic nerve section, retinas were enzimatically dissociated and the effects of excitatory and inhibitory neurotransmitters were tested on isolated RGCs. AMPA (100 µm) and kainate (30 µm) were unable of inducing ionic currents in RGCs from axotomized animals. GABA–induced currents (3–100 µm) were recorded in RGCs dissociated from axotomized animals although their amplitude decreased to 20 % of those recorded in RGCs from control retinas. The immunohistochemistry for Glut6/7 showed a relevant labeling of somas in the ganglion cell layer of control animals. However, no labelling of RGCs was observed in the ganglion cell layer of retinal sections from axotomized eyes. Immunohistochemistry for α1 subunit of the GABA receptors strongly labeled amacrine cells somas and cell processes in the inner plexiform layer, corresponding to characteristic stratification pattern. One month after axotomy, significant changes in the stratification were observed, although GABA receptor labeling persisted.
Our results indicate that axotomy of RGCs induce adaptive changes in the expression of GABA and Glutamate receptors. Decrease in neurotransmitter receptors is also demonstrated by functional techniques.
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