The Expression Of GAP-43 In 17 Area Of Visual Cortex In Form-Deprived Amblyopic Kittens

ObjectiveTo investigate expression of GAP-43, a growth associated protein, in 17 Area of visual cortex in monocular form-deprived amblyopia model and the model treated with levodopa. The possible mechanism of monocular form-deprived amblyopia and therapeutic effect of levodopa are discussed.MethodsFifty kittens of 4-week-old were randomly divided into five groups: normal group, monocular form-deprived group, control group, low-dose group, high-dose group, each group had ten cats. The left eyelids were sutured in behind four groups at 4-week-old.The kittens were raised for 4 weeks and were assured the formation of amblyopia by PVEP. Then ten kittens were killed in monocular form-deprived group; the right eye of the kittens in the control group were sutured as a model of patch therapy for 4 weeks; the kittens in the low-dose group and the high-dose group were daily received with levodopa of 20mg/kg and 80mg/kg for 4 weeks separately.5 kittens were killed at 8-were-old and others were killed at 12-week-old by PVEP in normal group. The visual cortex 17 area of right brain were obtained to observe morphology and immunohistochemistry in all kittens.Result(1)Electrophysiology: At 8-week-old, the latency and ampitude of P₁₀₀ of PVEP was significantly delayed and declined in monocular deprived eyes of monocular form-deprived group control group, low dose and high dose group, compared with fellow eyes and normal eyes (P<0.05). At-12-week-old,the amptitude of low dose group in monocular deprived eyes is no significant difference compared with fellow eyes and normal eyes (P>0.05);but the lantency did not recover to normal(P<0.05).In high group, the amptitude and lantency recovered to normal, presenting a insignificant difference compared with fellow eyes and normal eyes(P>0.05). (2)Morphology: compared with the normal group, numbers of neuron in the form-deprived group decrease and most of them, appearance of neuron is not regular, volume of neuron is unequal, ecphyma of neuron is getting shorter or disappearance. Some nucleus of neurons are smaller and darkening. After administration of levodopa, most of neurons are recovered and the volume of neuron is bigger and the axon is recovered in the high-dose group .But in the low-dose group and the control group, few of neurons recovered.(3)Immunohistochemistry: Compared with the normal group, the expression of GAP-43 is significant difference in the form-deprived group (P<0.05). The expression in high-dose group is similar to the normal group and no significant difference is found (P>0.05) . Compared with the normal group, there is significant difference between the control group and the low-dose group (P<0.05).Conclusions(1)There is significant increase of the expression of GAP-43 in the form-deprived group compared with the normal group. It indicates that GAP-43 may play a important role in formation of amblyopia.(2)There is significant decrease of the expression of GAP-43 in the high-dose group with levodopa. It suggests that the improved visual function of amblyopia may be brought into effect through GAP-43 expression.