The Effect Of Early Stress On Visual Plasticity In Mice

Early stress affects individual neuroendocrine activity and cognitive function, then cause long-term impact on individual health, including behavioral changes and increased susceptibility to mental illness in adulthood. Most of the previous studies focused on the impact of early stress on the depression or other mental illnesses, while giving less attention to the sensory function. This study mainly explores the influence of early stress on the visual system development.The development of the nervous system is regulated by both genes and postnatal environment. Genes affect the prenatal development of the nervous system. Meanwhile, the external environment further refines the nervous system after birth. Synaptic connections could be modified with the external experience, named as "plasticity". In a time window during development, neural connection is the most sensitive to the experience. We call this period as the "critical period". The onset and the end of the critical period is associated with many factors, including functional factors, such as GABAergic and glutaminergic system, and structural factors such as the perineuronal nets (PNN), and epigenetic factors under gene regulation. Ocular dominance plasticity is a classic model of the visual plasticity.To study whether early stress affect the development of the visual system, we first set up the early stress model in C57BL6 mice. Then we measured the response of neuron in V1 to bilateral visual input by in vivo electrophysiological recording. In addition, we examined the effect of early stress on the development of visual acuity with intrinsic optical imaging. Last, we studied the molecular mechanism by Western blot. We found:1) In the peak of the critical period, we observed significant ocular dominance shift following 4 days of monocular deprivation in mice with early stress, suggesting that early stress had no effect on the magnitude of ocular dominance plasticity. However, early stress delayed the onset and the end of the critical period.2) In adult mice suffered from early stress, we still observed ocular dominance shift by MD. No ocular dominance shift was observed in normal adult mice.3) Early stress may affect the development of visual acuity in mice. Visual acuity of experimental mice was generally lower than that of control mice. There was significant difference between the visual acuity of two groups at the end of criticalperiod.4) The expression of GAD67 is reduced in visual cortex of infant mice after early stress.In conclusion, early stress affects the maturation of visual cortex in mice. This effect may be through the connection between different brain areas. Due to the change of certain molecules, the balance of excitatory and inhibitory signal pathways in CNS is broken, and then the neural network will be unstable. Our new point of view about the effect of stress on visual function and development would be important to further understand the negative effect of stress and the development of visual system.