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Y.–C. Chang, C.–C. Chiao; Expression of Ionotropic Glutamate Receptors in the Developing Rabbit Retina . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2789.
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© ARVO (1962-2015); The Authors (2016-present)
Glutamate has been suggested to regulate the development of retinal neurons, but ontogenic expression of ionotropic glutamate receptors has only recently been characterized in the rat retina. It has been shown that retinal waves in rabbits switch from the fast cholinergic drive to the fast glutamatergic drive in P1–P3. In this study, we aimed to examine the expression patterns of AMPA receptors, and to functionally map glutamatergic drive in the developing rabbit retina.
The retinas from New Zealand White rabbits of different developmental stages (postnatal day 0 to 10, and adult) were isolated and cryosectioned into vertical slices. Antibodies against GluR1, GluR2/3, and GluR4 were used to examine the postnatal expression patterns of AMPA receptor subunits. To further map glutamatergic drive in the developing rabbit retina, the agmatine (AGB) activation assay developed by Marc (1999) were employed in this study.
All AMPA receptor subunits, including GluR1, GluR2/3, and GluR4, expressed in both the inner and the outer plexiform layers (IPL and OPL) at birth. However, the expression of GluR1 and GluR4 subunits were weak in P0 and P2, and showed a striking increase from P4 to P6. In contrast, the expression of GluR2/3 subunits was strong in the IPL from P0, while the expression in the OPL was not strong until P6. The AGB activation assay revealed that some amacrine and ganglion cells can be activated with 2 µM AMPA from P0, and with increased concentration of AMPA (20 µM), some horizontal cells can be activated at the same stage. In contrast, higher concentration of NMDA (500 µM) was required for activating some ganglion cells from P0 and a few amacrine cells from P2.
Ionotropic glutamate receptors were expressed and functioning in early stages of the developing rabbit retina. This expression pattern coincides with the switch of glutamatergic drive of the retinal wave, and may contribute to the synaptic maturation in the retinal circuits.
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