Experimental Study On Synaptic Plasticity Of Visual Cortex In Monocular Deprivation Amblyopia Rats

Purpose:To explore the regulation of changes of synaptic ultrastructure at the 17th area of primary visual cortex of monocular deprivation amblyopia rats within cortical period, and the expression of tissue-type plasminogen activator, and to discuss the relationship between the plasticity of synapse and amblopia.Methods:Establishing the model of monocular deprivation amblyopia rat. After proving the model successfully by PVEP, rats of both the amblyopia and the control were sacrificed to get the 17th area of primary visual cortex at 7d, 21d, 35d and 49d’ s old: (1)Electron microscope was used to study the changes of synaptic ultrastructure. 3,000 photoes were captured consecutively from layerⅠtoⅥof the primary visual cortex to count the number of synapses. 30,000 photoes were captured randomly, and Image Proplus 6.0 computer image analysis was applied to measure synaptic cleft width, post-synaptic density thickness and synaptic interface curvature. SPSS11.5 was used to get the results. (2)Frozen slice were made to measure the expression of tissue-type plasminogen activator using Immunofluorescence staining.Results:(1)PVEP:Compared with the control, in monocular deprivation amblyopia rats, the amplitude was attenuated when driven by the deprived eye, and the latent period was delayed (P>0.05).(2) Changes of synaptic ultrastructure:Monocular deprivation amblyopia rats showed significant decreases in the number of synapses and synaptic interface curvature, while showed significant increases in post-synaptic density thickness and the cleft width, as compared with the control at 35d and 49d s old (P<0.05).There are no significant differences at 21d’ s old (P>0.05).(3) Expression of tissue-type plasminogen activator: In control rats,no tPA was found in visual cortex of 7d group,while in other groups, tPA was seen majorly in layerⅡ-Ⅲ. In monocular deprivation amblyopia rat,the density of tPA-containing cells was higher than the same day old control ones, reaching peak at 21d and weakening gradually.Conclusion:(1) Amblyopia led to remarkable changes of synaptic number and ultrastructure at the 17th area of primary visual cortex, which greatly reduced the efficiency of synaptic transmission.(2)TPA was participated in the plasiticity of ocular dominance columns. Whether tPA can be used in the drug therapy of amblyopia will be a new field.