Visual experience-independent functional expression of NMDA receptors in the developing rabbit retina.
OBJECTIVE
Activation of the NMDA glutamate receptors is critical for the initiation of synaptic plasticity. In the developing rat retina, NMDA receptor function has been associated with visual experience, though the light-dependent regulation of the subunit composition of the NMDA receptors is controversial. In the present study, the functional expression of NMDA receptors in the developing rabbit retina was characterized and the impact of light deprivation on how the subunit composition of NMDA receptors is regulated was examined.


METHODS
Antibodies against NR1 and NR2A/B were used to examine neonatal expression patterns of the NMDA receptor subunits. Furthermore, the functional NMDA receptors were mapped using the agmatine (AGB) activation assay.


RESULTS
Although NR1 and NR2A/B subunit immunoreactivity was prominently detectable only immediately after birth, AGB activation assay showed that functional NMDA receptors could be identified as early as embryonic day 21. No significant difference was observed between normal- and dark-reared animals in terms of their NR1 and NR2A/B expression. In addition, a comparison of AGB permeation between normal- and dark-reared animals showed no difference in functional expression of NMDA receptors.


CONCLUSIONS
These results indicate that NMDA receptors participate in the synaptic maturation of retinal circuits during the early stages of development but that the functional NMDA receptors, including their subunit composition, in the developing rabbit retina are independent of the rabbit's visual experience.
Chang
Yun-Chieh
YC
Institute of Molecular Medicine, National Tsing Hua University, Hsinchu, Taiwan.
Chen
Chih-Yang
CY
Chiao
Chuan-Chin
CC
D000376:Agmatine / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D003623:Dark Adaptation / Q000502:physiology*; D019084:Fluorescent Antibody Technique, Indirect; D018613:Microscopy, Confocal; D009473:Neuronal Plasticity / Q000502:physiology; D011817:Rabbits; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D012160:Retina / Q000187:drug effects / Q000196:embryology* / Q000378:metabolism; D055351:Retinal Neurons / Q000502:physiology; D014785:Vision, Ocular / Q000502:physiology*
C409466:NR1 NMDA receptor; C120997:NR2A NMDA receptor; C121001:NR2B NMDA receptor; D016194:Receptors, N-Methyl-D-Aspartate; D000376:Agmatine