Effect Of NGF On The Binocular Fusion Of Cats

ObjectiveTo investigate the expression of nerve growth factor(NGF) in the 17th area of different ages normal cats'visual cortex, so that we can find the probable mechanism of the binocular fusion and the possible factors relating to it.Methods12 healthy cats aged 2～3 weeks were used in our study. They were divided into four groups. We tested the amplitude and latency of P wave of two eyes of each cats in those four groups when they grew up to 4 weeks,6 weeks,12 weeks and 16 weeks by using pattern visual evoked potentials (PVEP), to compare the differences of P wave between both eyes of various ages cats. We also use immunohistochemistry to observe differences of the expression of NGF in the binocular fusion center (the 17th area of visual cortex) among different aged normal cats, to see the effect of NGF on binocular fusion.ResultsThe differences of the amplitude and latency of P wave between two eyes of each cats in those four groups had no statistical significance (P>0.05), which showed us that there were no obvious differences between two eyes of normal cat. From the data we had got, we could see that the amplitude of P wave gradually increased and the latency decreased as normal cats got older. We observed the expression of NGF in theⅡ～Ⅳlayers of the 17th visual cortex, most of them are granulosa cells, and found that the expression amount of normal cat began to increase from 4 weeks old, reached its maximum at 6 week, and then fell off gradually. The expression at week 12 was almost decrease to the level of week 4, but still higher than it. When the cats got 16 weeks old, the expression amount declined significantly lower than week 4. The expression differences at 6 weeks compared with 4 weeks,6 weeks and 12 weeks were highly statistically significant (P<0.001), the difference between 4 weeks and 12 weeks had statistical significance (P<0.05), and were highly statistically significant with 16 weeks (P<0.001).ConclusionWith increasing age normal cats, amplitude of P wave increased, and latency decreased. PVEP can simply reflect the development of binocular visual function. It means that as growing up, the vision of cats is developing. According to the different expression inⅡ～Ⅳlayers of the 17th visual cortex normal kittens, we can know that NGF is associated with the development and formation of binocular fusion. Binocular fusion increases with age, the most significant development happens in the critical period of visual plasticity at about 6 weeks, then decrease gradually. NGF expression keep a high degree of consistency with the critical period of visual development, which indicating that NGF is an important molecules basis of the plasticity of binocular fusion.