| Aging issue seriously affect the life quality of people.Aging can cause serious damage to the various functions of the visual system of the eldly.However,previous studies have shown that degradation of the optical system affected by aging could not completely account for all of the visual dysfunction effects,so it has been show that there should be age-related declines in the visual cortex occurring in the process of aging.Previous studies have found that the visual cortical functions of animals are affected by aging,such as spatial and temporal frequency response properties,orientation and direction selectivity,contrast sensitivity,response variability,response latency,and so on.Neurotrophins,such as BDNF,regulate nearly all aspects of neural circuit development and function,including cell proliferation and differentiation,axon and dendrite growth,synaptogenesis,and synaptic function and plasticity,and higher cognitive functions.The level of BDNF decreased significantly in aging cortex.Previous studies have shown that there is a significant correlation between the decline of BDNF/TrKB signal in the primary visual cortex with the decrease of visual acuity and spatial sensitivity.Therefore,the degeneration of BDNF/TrkB signal system may be a potential mechanism for the decline of visual cortical functions.7,8-dihydroxyflavone is a small molecule TrkB receptor agonist.Compared to BDNF,7,8-dihydroxyflavones can pass through the blood-brain barrier and have better pharmacological potency.Thus,as a BDNF alternative,7,8-dihydroxyflavone provides a new therapeutic approach for many neurodegenerative diseases.To understand the effects of 7,8-dihydroxyflavone on the functional properties of the aged visual cortex.We infused exogenous 7,8-dihydroxyflavone into the V2 region of the old rhesus monkey by intravenous administration and topical administration.We investigated a series of changes in neuronal response propertiess before and after administration.The results showed that:(1)The spatial frequency response properties:In both drug ways,the spatial frequency tuning bandwidths of neurons decreased significantly.This may be achieved by increasing the inhibitory effect of neurons on non-optimal stimuli,increasing the resolution ability of spatial frequency;But the optimal spatial frequencies of neurons were not changed.This may be because our experiment is acute administration,which is caused by short-term effects.(2)Contrast sensitivity:In both drug ways,the contrast threshold of neurons decreased significantly,the contrast sensitivity was improved,indicating that the visual cortex functional injury was significantly improved.The contrast gain was also improved,means that the restored of the balance of the excitement-inhibitory system.(3)Response variability and the signal-to-noise ratio:In both drug ways,the response variability of neurons decreased significantly.We speculate that this also means that the restored of the balance of the excitement-inhibitory system.Associated with response variability,the SNR was improved,indicating that the information processing capacity of neurons was improved.(4)Noise correlation:In both drug ways,the noise correlation of the population was significantly reduced.This means that the coding efficiency of the neuron population was improved and the accuracy of the information processing was increased.These results suggested that 7,8-dihydroxyflavone can significantly improved the visual function of V2 neurons in senscent monkeys.The possible mechanism was to repair the damage of BDNF/TrkB signal system caused by aging,affected the the balance of the excitement-inhibitory system in Cortical circuits,thereby improved the neuronal response properties.Our study provides some new insights for the potential mechanism of aging in the visual cortex.At the same time,the study of intravenous administration of 7,8-dihydroxyflavone provided new physiologic evidences for the recovery of brain function in the elderly and the treatment of neurodegenerative diseases. |
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