Study on the cortical synaptic density and visual function in monocular form deprivation rats with amblyopia / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM: To study the effect of monocular form deprivation(MD)on the synaptic density in the visual cortex of the amblyopic rats during the critical period of visual development, the visual cortical synaptophysin(SYN)expression and significance of its expression, as well as the relationship between the synaptic density and the visual function. This research will provide mechanisms underlying the pathogenesis and clinical treatment of amblyopia.<p>METHODS: Normal newborn Long Evans rats were randomly divided into normal control group and amblyopia model group, each with 16 rats. Both groups of rats were raised in the same environment. The normal control group did not receive any treatment. On the 13d after birth, the amblyopic model group received monocular suture to establish a classic monocular form deprived amblyopic model. Both groups of rats were received Visual evoked potential(F-VEP)detection on the 51d. Samples were taken immediately after the detection. The transmission electron microscope and Image J image analysis software were used to observe and analyse the synaptic density in the V1M of the primary visual cortex of the two groups of rats. Frozen sections of visual cortex were stained by immunofluorescence histochemical staining by bleaching method and the expression of SYN positive neurons was observed and quantitatively analyzed. <p>RESULTS: F-VEP examination showed that compared with the normal control group, the P2 latency of the deprived eyes in the amblyopic group was significantly long, and the amplitude of P2 wave was significantly lower than that of normal eyes(<i>P</i><0.05); Transmission electron microscopy results showed that the synaptic density of the bilateral visual cortex of the amblyopic model group was significantly reduced compared with the normal control group(<i>P</i><0.05), the contralateral visual cortex of the amblyopic eye decreased more significantly(<i>P</i><0.05); immunofluorescence staining results showed that the brain slices in the visual cortex of the two groups were intact and the tissue structure was clear under the microscope. Compared with the normal control group, the expression intensity of SYN positive neurons in the amblyopic group was significantly reduced(<i>P</i><0.01).<p>CONCLUSION: There is structural synaptic plasticity during the critical period of visual development. Monocular form deprivation can reduce the synaptic density, SYN expression and the visual function in the primary visual cortex of the amblyopic rats.

Influence of enriched environment on visual function and synaptic plasticity in adult amblyopic mice / 中华实验眼科杂志

Objective To examine role and possible mechanism of enriched environment (EE) on regulating recovery of visual function in adult monocular deprivation amblyopia mice.Methods A total of 72 healthyKunming mice were divided into normal control group,monocular deprivation (MD) group,MD+EE group and M D+ fluoxetine group by random number table.Except for the normal control group,the mice in the other groups were sutured on the right eyelid 21 days after birth to establish MD amblyopia model.the mice were fed in standard environment or EE for 4 weeks according to the group.Visual acuity and flash visual evoked potential (F-VEP) of mice in each group were detected.The distribution of microtubule associated protein 2 (MAP2) in visual cortex of adult amblyopic mice were detected by immunohistochemistry.The expression of MAP2,synaptophysin (SYP) and postsynaptic density protein-95 (PSD-95) protein in visual cortex of adult amblyopic mice were detected by western blot.The experimental protocol was approved by the Animal Care and Use Committee of Hunan Children's Hospital and conformed to the National Institutes of Health Guide for the Care and Use of Laboratory Animals.Results There was a significant difference in the visual acuity of deprived eye among each group (F=114.632,P＜0.001).The visual acuity in MD group is lower than that in normal control group,with a significant difference (t =15.480,P＜0.001).Compared with MD group,visual acuity was restored in MD+ EE group and MD +fluoxetine group,with significant differences (t =15.071,P ＜ 0.001;t =14.841,P ＜ 0.001).There was a significant difference in the P2 latency and amplitude of F-VEP in deprived eye among each group (F=36.510,P=0.000;F=34.140,P=0.000).Compare with normal control group,P2 latency was prolonged and P2 amplitude of F-VEP was decreased in deprived eye in MD group,with significant differences (t =10.220,P =0.000;t =10.09,P =0.000).Western blot assay showed that there was a significant difference in the expression of MAP2 in visual cortex contralateral deprived eye among each group (F=18.142,P=0.000).The expression of MAP2 in MD group was significantly lower than that in normal contral group (t=3.056,P＜0.01);Compared with MD group,MAP2 expression was increased in MD+EE group and MD+fluoxetine group (t =2.541,P =0.031;t =2.157,P =0.017).There were significant differences in the expression of SYP and PSD-95 in visual cortex contralateral to deprived eye among each group (F =12.871,P =0.000;F =25.060,P =0.000).Compared with normal contral group,SYP and PSD-95 expression in visual cortex were down-regulated in MD group,with significant differences (t =6.054,P =0.000;t =8.631,P =0.000).The expression of SYP and PSD-95 protein in MD+EE group and MD+fluoxetine group were significantly higher than those in MD group (all at P＜0.05).Conclusions EE can recover visual function through up-regulating the expression of MAP2,which can modulate the dendritic branch trim and neural plasticity of visual cortex in adult MD mice.

Reactivation of visual cortical plasticity by caloric restriction mediated by AMPK-SIRT1 pathway from monocular deprivation in adult mice / 中华实验眼科杂志

Objective This study was to investigate the effect of caloric restriction on the plasticity of visual cortex in adult monocular deprivation (MD) amblyopic mice,as well as to promote the treatment of amblyopia,and to explore the possible molecular mechanism of this benefical effect.Methods Fifty healthy newborn Kunming mice of clean grade were randomly divided into 3 groups using a random number table method:normal control group (n =14),MD+ ad libitum group (n=18) and MD+ caloric restriction group (n=18).A mouse model of adult MD amblyopia was established,and caloric restriction intervention and ad libitum were performed on MD + caloric restriction group and MD+ ad libitum group,respectively.The visual acuity and flash visual evoked potential (F-VEP) of each group were detected.The synaptic structure of visual cortex neurons was observed by transmission electron microscope,and the expression of phosphorylated AMP-activated protein kinase-α(p-AMPKα) and silent information regulator 1 (SIRT1) in visual cortex were detected by Western blot.The animal feeding and use was in accordance with the standards set by the ARVO.Results The weight of mice in MD+ caloric restriction group increased from the beginning of the first week,and was significantly lower than that in the MD + ad libitum group (P＜0.05).Compared with the MD+ ad libitum group,the visual acuity was restored,the latency was shortened,and the amplitude of F-VEP was increased in the deprived eyes of MD+ caloric restriction group (all at P＜0.05).Transmission electron microscope observation showed that the width of synaptic gap of visual cortical neurons was significantly narrower,and the thickness of postsynaptic density was significantly thicker in MD+ caloric restriction group than that in the MD+ ad libitum group (both at P＜0.05);compared with the normal control group,the synaptic gap was widened and the postsynaptic density was significantly thicker than that in the MD+ ad libitum group (both at P＜0.05).Western blot showed that the expression of p-AMPKα in visual cortex in the normal control group,MD+ caloric restriction group and MD+ ad libitum group was 0.89±0.03,0.94±0.02 and 0.74 ±0.02,and the expression of SIRT1 was 0.97±0.11,0.95±0.14 and 0.58±0.13,respectively,showing significant differences among the three groups (F =14.57,P =0.00;F=23.91,P=0.00),the expressions of p-AMPKα and SIRT1 in visual cortex were increased in MD+ caloric restriction group than those in M D+ ad libitum group (both at P＜0.05).Conclusions Caloric restriction can restore the ultrastructure of synapses and improve the visual cortical plasticity in adult MD mice,so that help to improve visual function.Its mechanism may be related to the activation of AMPK-SIRT1 pathway.

Intervention of acupuncture on abnormal spatiotemporal pattern of visual cortex area 17 neuron in monocular deprivation amblyopia rats / 中国针灸

<p><b>OBJECTIVE</b>To preliminarily explore the electrophysiological mechanism of acupuncture on plasticity variability of visual cortex.</p><p><b>METHODS</b>Fifty 14-day-old Wistar rats were randomly divided into a blank group, a model group, an early-stage acupuncture group, a middle-stage acupuncture group and a late-stage acupuncture group, 10 rats in each one. Except the blank group, the rats in the remaining groups were treated with eyelid suture to establish the model of monocular deprivation amblyopia. After model establishment, the rats in the blank group and model group were grasped without any intervention everyday. The rats in the acupuncture groups were treated with acupuncture at bilateral "Jingming" (BL 1), "Cuanzhu" (BL 2), "Fengchi" (GB 20) and "Guangming" (GB 37) on the 3rd, 12th and 21st days into model establishment. The needles were retained for 10 min, once a day for totally 9 days. After treatment, the M-NEMEA technology was applied to measure the discharge amplitude and power spectral density of visual cortex area 17 neuron of each group.</p><p><b>RESULTS</b>Compared with the blank group, the number of discharged neuron of visual cortex area 17 was reduced, and the amplitude was significantly reduced in the model group (both<0.05). Compared with the model group, the numbers of discharged neuron were increased, and the amplitudes were significantly increased in the early-stage acupuncture group and middle-stage acupuncture group (all<0.05). The neuron discharge amplitude in the early-stage acupuncture group was higher than those in the middle-stage acupuncture group and late-stage acupuncture group (both<0.05); the neuron discharge amplitude in the middle-stage acupuncture group was higher than that in the late-stage acupuncture group (<0.05). In the 120-second time domain of acquisition, the distribution of power spectral density in the blank group was mainly between -105 dB and -100 dB; compared with the blank group, the power spectral density in the model group was increased and distributed between -132 dB and -124 dB; compared with the model group, the power spectral densities in the acupuncture groups was reduced and distributed between -115 dB and -110 dB in the early-stage acupuncture group, -120 dB and -115 dB in the middle-stage acupuncture group and -129 dB and -122 dB in the late-stage acupuncture group.</p><p><b>CONCLUSIONS</b>There are abnormal changes of spatiotemporal pattern in visual cortex area 17 of monocular deprivation rats, but acupuncture can regulate abnormal spatiotemporal pattern of neuron. Therefore, there is developmental plasticity of visual cortex neuron in the sensitive period, and early treatment is key to superior efficacy.</p>

Effects of monocular deprivation on the dendritic features of retinal ganglion cells / Efectos de la privación monocular sobre las características dendríticas de las células ganglionares de la retina

Monocular deprivation results in anatomical changes in the visual cortex in favor of the non-deprived eye. Although the retina forms part of the visual pathway, there is scarcity of data on the effect of monocular deprivation on its structure. The objective of this study was to describe the effects of monocular deprivation on the retinal ganglion cell dendritic features. The study design was quasi-experimental. 30 rabbits (18 experimental, 12 controls) were examined. Monocular deprivation was achieved through unilateral lid suture in the experimental animals. The rabbits were observed for three weeks. Each week, 6 experimental and 3 control animals were euthanized, their retina harvested and processed for light microscopy. Photomicrographs of the retina were taken using a digital camera then entered into FIJI software for analysis. The number of primary branches, terminal branches and dendritic field area among the non-deprived eyes increased by 66.7%(p=0.385), 400%(p=0.002), and 88.4%(p=0.523) respectively. Non-deprived eyes had 114.3% more terminal dendrites (p=0.002) compared to controls. Among deprived eyes, all variables measured had a gradual rise in the first two weeks followed by decline with further deprivation. There were no statistically significant differences noted between the deprived and control eyes. Monocular deprivation results in increase in synaptic contacts in the non-deprived eye, with reciprocal changes occurring in the deprived eye.

La privación monocular de la visión resulta en cambios anatómicos en la corteza visual en favor del ojo no privado. Aunque la retina forma parte de la vía visual, hay escasez de datos sobre el efecto de la privación monocular en su estructura. El objetivo de esta investigación fue describir los efectos de la privación monocular en las características de las dendritas de las células ganglionares de la retina. Se diseñó un estudio cuasi-experimental. Se examinaron 30 conejos (18 experimentales, 12 controles). La privación monocular se logró a través de la sutura unilateral del párpado en los animales de experimentación. Los conejos fueron observados durante tres semanas. Cada semana, 6 animales experimentales y 3 control fueron eutanasiados, donde se obtuvo la retina y fue procesada para realizar microscopía óptica. Las microfotografías de la retina fueron tomadas con una cámara digital y luego se utilizó el software FIJI para su análisis. El número de dendritas primarias, terminales y el área del campo de dendritas en los ojos no privados aumentó un 66,7% (p=0,385), 400% (p=0,002), y 88,4% (p=0,523), respectivamente. Los ojos no privados, tenían 114,3% más dendritas terminales (p=0,002) en comparación con los controles. Entre los ojos privados, todas las variables medidas tuvieron un aumento gradual en las dos primeras semanas, seguido de descenso con mayor privación. No se observaron diferencias estadísticamente significativas entre los ojos privados y el grupo control. En conclusion, la privación monocular produce un aumento de los contactos sinápticos en los ojos no privados, con cambios recíprocos que se manifiestan en los ojos privados de la visión.

Influences of levodopa and cytidine diphosphate choline on the expression of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid GluR2 in visual cortex of monocular deprivation rats / 中华实验眼科杂志

Background Research demonstrated that alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid GluR2 (AMPA-GluR2) is associated with amblyopia.It has been shown that levodopa and cytidine diphosphate choline can improve visual function of amblyopic children,but the mechanism is unclear.Objective This study was to explore the possible effects of levodopa and cytidine diphosphate choline on amblyopia.Methods Monocular deprivation (MD) animal models were created in 60 2-week-old SD rats by monolateral eyelid suturing and observed for 31 days and reared in natural light together with 15 other matched normal healthy SD rats.The models were randomly divided into the MD group,levodopa group,cytidine diphosphate choline group and normal saline control group,with 15 rats for each group.40 mg/kg of levodopa,80 mg/kg of cytidine diphosphate choline,I ml normal saline were given to the rats,respectively,for 28 consecutive days.Expressions of the AMPA-CluR2 protein and AMPA-CluR2 mRNA in the rat visual cortex were detected by immunohistochemistry,Western blot and real-time fluorescence quantitative PCR.Use of the animals followed the Regulations for the Administration of Affairs Concerning Experimental Animals by State Science and Technology Commission.Results The expression values of the AMPA-GluR2 protein (AMPA-GluR2/β-actin) and AMPA-GluR2 mRNA (2-△△Ct) were significantly lower in the MD group than those of the normal control group (protein:0.32 ± 0.02 vs.0.64 ± 0.05,t =13.287,P＜0.05 ;mRNA:0.30±0.01 vs.0.84±0.03,t=38.184,P＜0.05).Those in the levodopa group were significantly increased in comparison with the normal saline solution group (protein:0.59 ±0.04 vs.0.33 ±0.03,t =11.628,P＜0.05 ; mRNA:0.71±0.06 vs.0.33 ±0.02,t =13.435,P＜0.05).The expression values of the AMPA-GluR2 protein and AMPA-GluR2 mRNA were significantly increased in the cytidine diphosphate choline group compared with the normal saline solution group (protein:0.52 ± 0.04 vs.0.33 ± 0.03,t =8.497,P ＜ 0.05 ; mRNA:0.48± 0.04 vs.0.33 ± 0.02,t =7.500,P＜0.05).Conclusions AMPA-GluR2 is associated with the plasticity of visual development.Levodopa and cytidine diphosphate choline may improve visual function by down-regulating the expression of AMPA-GluR2 in the visual cortex.

Enriched environment contributes to recovery of visual acuity and increases perineuronal nets in monocular-deprived animals

The aim of the present study was to analyze the influence of enriched environment on the distribution of perineuronal nets (PNNs) using a stereogically based unbiased protocol and visual acuity in adult Swiss albino mice that underwent monocular deprivation during the critical period of postnatal development. Eight female Swiss albino mice were monocular deprived on postnatal day 10 and divided into two groups at weaning: standard environment (SE group, n = 4) and enriched environment (EE group, n = 4). After 3 months, all of the mice were subjected to grating visual acuity tests, sacrificed, and perfused with aldehyde fixative. The brains were removed and cut at 70 µm thickness in a vibratome and processed for lectin histochemical staining with Wisteria floribunda agglutinin (WFA). Architectonic limits of area 17 were conspicuously defined by WFA histochemical staining, and the optical fractionator stereological method was applied to estimate the total number of PNNs in the supragranular, granular, and infragranular layers. All groups were compared using Student's t-test at a 95 percent confidence level. Comparative analysis of the average PNN estimations revealed that the EE group had higher PNNs in the supragranular layer (2726.33 ± 405.416, mean ± standard deviation) compared with the SE group (1543.535 ± 260.686; Student's t-test, p = .0495). No differences were found in the other layers. Visual acuity was significantly lower in the SE group (0.55 cycles/degree) than in the EE group (1.06 cycles/degree). Our results suggest that the integrity of the specialized extracellular matrix PNNs of the supragranular layer may be essential for normal visual acuity development.