Aged-related Changes Of Brain Derived Neurotrophic Factor And γ-aminobutyric Acid Expression In The Visual Cortex Of Rat

Senescence can lead to a progressive functional declines of visual system in visual signal processing. The underlying neural mechanisms remain unclear. The primary visual cortex plays important roles in preliminary processing of visual signal(such as shape,color,size,shade,direction,depth and so on).The age-related structural and functional changes of neurons might be one of the important factors which cause the senile visual ability drops. Therefore, comprehensive research age-related structure and function of the primary visual cortex changes has an important theoretical and practical value in improving and enhancing the life quality of the elderly,preventing premature aging of vision functions with medical way.The research has shown that the age-related declining of cognitive ability and long-term memory ability may be linked to the decrease expression of brain derived neurotrophic factor in the nervous system and the cortex inhibitory neurotransmitter γ-aminobutyric acid. Therefore,this study compared the expression changes of brain-derived neurotrophic factor(BDNF) and inhibitory neurotransmitter γ-aminobutyric acid(GABA) in the primary visual cortex between different age groups of rats, and trying to provide clues for exploring the cellular molecular mechanisms that underlie senescence-related visual function declines. Healthy male SD rats with young(n=6),middle-aged(n=6) and old groups(n=6) were used as subjects in the experiment. Brain tissue containing the primary visual cortex(V1) were obtained and cut serial frozen sections. Nissl staining and Immunohistochemical methods was applied to show visual cortical layers and display the BDNF and GABA-immunopositive neurons in the primary visual cortex of rats respectively. Sections were observed, photographed, measured and statistical analyzed with Image-Pro Express 6.0 software. The results show that the mean density of Nissl-stained neurons in each cortical layer of V1 showed no significant difference. Compared to the young group of rats, the average density and immunoreactive intensity of BDNF and GABA-positive neurons in each cortical layer of V1 in middle-aged and old groups of rats were significantly decreased. The average density and intensity of BDNF and GABA-immunoreactive neurons in each cortical layer of V1 in old group of rats were significantly lower than those in the middle-aged ones. The reduction of GABA expression in each cortical layer of V1 is highly correlated to the decrease of BDNF expression during the aging process. The experiment results suggest that the expression of BDNF in the primary visual cortex of different groups of rats showed a progressive decline from middle-aged to old-age, the reduction of BDNF secretion may result in a down-regulation of GABA expression in the brain. which may be an important mechanisms that mediates the visual function declines during aging.