The Investigation On Synaptic Plasticity At The 17th Area Of Adult Rat's Visual Cortex

ObjectiveTo explore the effect of reverse suture after monocular deprivationon synaptic plasticity at the 17th area of amblyopic rat visual cortex after the critical period of visual development, as well as the possible mechnism of synaptic plasticity in adult rat visual cortex.MethodsThe Wistar rats were divided into normal group, amblyopia group and reverse-suture group, and were sacrificed to obtain the 17th area of the left visual cortex at corresponding time points. The expression of GABAARα1 and GluR2 subunit was detected by immunohistochemistry. The changes of synaptic ultra-structure were observed by electron microscopy. Photos of 3,000 magnification were continuously captured from layer VI of the primary visual cortex for counting the number of synapses in 3,000 Multiplying Factor. Photos of 30,000 Multiplying Factor were captured randomly. Image Proplus 6.0 was used to measure the width of synaptic cleft, the thickness of post-synaptic density and synaptic interface curvature. SPSS 13.0 was used for statistical analysis.ResultsBy immunohistochemistry, weaker expression of GABAARal subunit could be found in the amblyopia group and reverse-suture group than in the normal group at P11w (P<0.001).The expression in the amblyopia group was weaker than the reverse-suture group (P<0.001). At P13w, the weaker expression could also be found in the amblyopia group than the reverse-suture group and the normal group(P<0.001), but there was no significant difference between the reverse-suture group and the normal group (P=0.496). The expression of GluR2 was stronger in amblyopia group than in reverse-suture group and normal group (P<0.001), weaker expression was seen in reverse-suture group than in normal group (P<0.001), either at Pllw or at P13w. Regarding changes of synaptic ultra-structure, there was significant difference among three groups both at Pllw and at P13w. The quantity of synapses in the amblyopia group reduced significantly compared with the reverse-suture group and the normal group, the quantity in the reverse-suture group was reduced than the normal group (P<0.01). The synaptic cleft was widened, synaptic PSD was thickened and interface curvature became smaller in the amblyopia group than the reverse-suture group and the normal group both at P11w and at P13w (P<0.05). The same result was taken when the reverse-suture group was compared with the normal group at P11w(P<0.05), but there was no significant difference at P13w(P>0.05). ConclusionThe plasticity of visual cortex exists not only in the critical period but also after the critical period of visual development. The reverse suture after monocular deprivation could improve the synaptic plasticity in visual cortex of adult rats in structure and function.