The expression of vasoactive intestinal polypeptide in the visual cortex of the anisometropic amblyopia kittens

Objective To investigate the expression changes of vasoactive intestinal polypeptide (VIP) in visual cortex of the normal and anisometropic amblyopia kittens during development at the field of tectology and neurocyto-molecular biology,and to research the relation between VIP and plasticity of visual system.These studies offer a basis of reference in preventing and treating anisometropic amblyopia.Methods Sixteen normal kittens (about 4-week of age) were divided into two groups randomly.Eight kittens were deduced amblyopia by monocular chronic atropinization; four (2normal and 2 amblyopia) kittens were perused in every three weeks.Changes in number and optical density of immunopositive neurons of the expression of VIP-protein in the visual cortex area 17were analyzed with immuno-cytochemistry.Results were obtained from slides examined under the light microscope and by computer image analysis.Transmission electron microscope was used to observe the ultrastructure of the visual cortex neurons,and a light microscope was used to observe the shapes of the neurons.Results Statistics showed that there were immunopositive neurons which appear as brown color in the visual cortex area 17.The number and optical density of VIP immunoreactive positive cells in normal kittens were higher than in amblyopia kittens at the same age (P ＜0.05).The degree of expression between these two groups was significantly different.Ultrastructurally,in the control group,the nuclear membrane of most neurons was discernable and chromatin was evenly distributed within the nucleus.Abundant cytoplasm and tubular-shaped mitochondria were observed.These cells were also rich in Golgi bodies,ribosomes,and endoplasmic reticulum.In amblyopic kittens,nuclei of most neurons were aggregated,the number of ribosomes and Golgi bodies was reduced,mitochondria were swollen,and mitochondrial cristae were shortened or even absent.The endoplasmic reticulum was distended and reduced in magnitude.Conclusions Asymmetrical visual stimulation,such as anisometropia,reduces VIP expression and impairs the structure and functions of nerve cells in the visual cortex.VIP may play an important role in maintaining the plasticity of the visual system. Key words: VIP;  Anisometropic amblyopia;  Visual development;  Visual cortex;  Kittens