Effect of monocular form deprivation during the pre-critical period on dendritic spine density and morphology in V1 neurons

Objective  To investigate the effect of monocular form deprivation (MD) during the pre-critical period of visual development on the density and morphology of dendritic spines in mouse primary visual cortex (V1) neurons.

Methods  Twenty SPF male C57BL/6J mice with eyes opened on postnatal day 14 (P14) were selected and divided into MD and control groups using a random number table, with 10 mice in each group.The MD group was fed to P18 after 4 days of MD in the right eye, and the control group was raised to P18 under the same feeding conditions.All mice were decapitated after cardiac perfusion, and the sections were stained with the cell membrane fluorescent probe 1, 1′-dioctadecyl-3, 3′, 3′-tetramethylindocarbocyanine perchlorate, and imaged by laser scanning confocal microscopy to observe and compare the differences in density and morphology of dendritic spines in bilateral V1 neurons between the control group and the MD group.This study was approved by the Animal Ethics Committee of Tianjin Medical University (No.TMUaMEC2022004).

Results  The total density of dendritic spines in the V1 area on the left side of the control group, the right side of the control group, the left side of the MD group, and the right side of the MD group were (7.57±0.25), (7.42±0.25), (6.54±0.18), and (7.51±0.29)spines/10 μm, respectively, with a statistically significant overall difference ( F=3.818, P<0.05).The total density of dendritic spines in the left V1 area of mice in the MD group was significantly lower than that in the left side of the control group and the right side of the MD group, and the differences were statistically significant (both P<0.05).There was a significant difference in the proportion of the four types of dendritic spines in V1 neurons on both sides between the two groups ( χ ²=26.295, P=0.002).There was a significant difference in the proportion of the four types of dendritic spines between the left V1 of the MD group and the left and right V1 of the control group (both P<0.008 3).There was a significant difference in the filopodia-type dendritic spine density in bilateral V1 neurons between the two groups ( F=3.253, P<0.05).Compared with the left V1 area of the control group, the density of filopodia-type dendritic spines in the left V1 area of the MD group decreased significantly, with a statistical significance ( P<0.05).There was no significant difference in the density of thin-type, mushroom-type, and stubby-type dendritic spines in bilateral V1 area neurons between the two groups ( F=1.760, 2.618, 1.749; all P>0.05).

Conclusions  MD during the pre-critical period of visual development can cause a decrease in the total density of dendritic spines and significant changes in the compositional proportions in the V1 contralateral to the deprived eye, and is mainly manifested by a decrease in the number of filopodia, suggesting that abnormal visual experience can cause plastic changes in the number and structure of synapses in the visual cortex during the pre-critical period of visual development.

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