Duration 5min, Q&A 3min
The Effect of Enriched Environment on Synaptic Plasticity in Area 17 of Amblyopic Rat Visual Cortex
To explore the effect of enriched environment on synaptic plasticity in area 17 of amblyopic rat visual cortex, including changes of synaptic ultrastructure, the expression of Synapsin I, and the level of GluR2 subunit.
Right eyelids of all experimental rats were sutured through the critical period. The rats were randomly divided into the amblyopia group, standard environment, and enriched environment group on postnatal day 45 (P45). The sutured eyelids were opened on P46, and the rats were sacrificed on P60, P75, and P105, respectively. Electron microscopy was used to observe the changes of synaptic ultrastructure. Photos were captured consecutively from layer I to VI of the primary visual cortex to count the number of synapses. The width of synaptic cleft, the thickness of post-synaptic density, and synaptic interface curvature were measured. The mRNA expression of Synapsin I and GluR2 was detected by RT-PCR assay. The expression of GluR2/3 subunit was detected by immuno- histochemistry.
Results and Conclusion
The quantity of synapses in the amblyopia group and standard environment group was reduced significantly. The synaptic cleft was widened, synaptic interface curvature became smaller, and PSD was thickened. The quantity of synapses and the thickness of PSD in the enriched environment group on P60 were significantly different from the normal group, while the width of synaptic cleft and synaptic interface curvature were recovered. At 75 and 105 days of age, the enriched environment group had no significant difference from the normal group. The expression of Synapsin I mRNA in the amblyopia group and standard environment group at all ages decreased significantly compared with the normal group. The mRNA expression of Synapsin I in the enriched environment group did not increase on P60, but on P75 and P105 it increased significantly and even surpassed that in the normal group. The expression of GluR2/3 subunit increased in layers II to VI in the amblyopia group and standard environment group; it also increased in the enriched environment group on P60, but could only be found in layer VI on P75. On P105, the expression in the enriched environment group was almost the same as in the normal group.
In conclusion, the plasticity of visual cortex may exist not only in the critical period but also after the critical period. Enriched environment could increase the synaptic structural plasticity of amblyopic rats, but with time effect.
[ Keyword ]
amblyopia / visual cortex / synapse / enriched environment / Synapsin
[ Conflict of Interest ]