| Objective:1.A guinea pig monocular form deprivation model was established to observe whether monocular form deprivation causes a reduction in visual acuity in the deprived eye by measuring objective visual acuity at different time points,and whether there is a sequence of visual acuity changes with changes in diopter and axial length.2.To examine the expression of NMDAR1 and GABRR2 in the retinas of guinea pigs after long-term monocular form deprivation and their interrelationship,and to explore the significance of the two receptors in this model.3.To detect the expression of NMDAR1 and GABRR2 in V1 area of guinea pigs after long-term monocular form deprivation and the interrelationship between them,and to observe whether the expression of NMDAR1 and GABRR2 in V1 area and retina are similar or different.Methods:1.Twenty guinea pigs were randomly divided into monocularly form-deprived group(MFD)and normal control group(NC)at 2 weeks of age after birth.The refraction,axial length,and objective spatial frequency visual acuity of the guinea pigs in the two groups were measured before,1 week,4 weeks,and 8 weeks after form-deprivation by means of cycloplegic retinoscopy,A-scan ultrasonography,and sweep visual evoked potentials(SVEP),respectively.Corrective lenses were placed in front of the stimulated eyes to compensate for the induced relative myopia before measuring objective spatial frequency visual acuity.2.The relative expressions of NMDAR1 m RNA and GABRR2 m RNA in the retinas and corresponding V1 areas of form-deprived eyes,contralateral eyes and normal control eyes were measured by RT-PCR,and the expressions of NMDAR1 and GABRR2 proteins in retinas and corresponding V1 areas were detected by Western Blot.Results:1.From 0 to 1 week of form deprivation,the visual acuities of contralateral eyes in MFD group and normal control eyes were significantly improved,but not in form-deprived eyes.From 1 to 8 weeks of form deprivation,the visual acuity of form-deprived eyes was significantly different from that of contralateral eyes and normal control eyes(P<0.05);At the time point of 1 week of form deprivation,there was no significant difference in diopter and axial length between form-deprived eyes and contralateral eyes and normal control eyes.At the time points of 4 and 8 weeks of form deprivation,the diopter decreased significantly and the axial length increased significantly(P<0.05);The changes at four time points of form-deprived eyes showed that the diopter decreased and the axial length increased most significantly in form-deprived eyes from 1 to 4 weeks of form deprivation.2.The expression of NMDAR1 and GABRR2 in the retinas of form-deprived eyes were higher than those in the contralateral eyes and NC right eyes(P<0.05).The expression of GABRR2 in form-deprived eyes increased significantly compared with that of NMDAR1,and the difference of GABRR2/NMDAR1 in form-deprived eyes compared with that in contralateral eyes and NC right eyes was statistically significant(P<0.05).3.NMDAR1 expression was reduced and GABRR2 expression was increased in the left V1 area corresponding to form-deprived eyes of MFD compared with that in the right V1 area corresponding to contralateral eyes of MFD and the left V1 area of NC(P<0.05).The expression of GABRR2 in the left V1 area corresponding to form-deprived eyes increased significantly compared with that of NMDAR1,and the expression of GABRR2/NMDAR1 in the left V1 area corresponding to form-deprived eyes increased compared with that in the right V1 area corresponding to contralateral eyes and the left V1 area of NC(P<0.05).The expression of NMDAR1 in the right V1 area corresponding to the contralateral eye of MFD was reduced compared with that in the right V1 area of NC(P<0.05),GABRR2 expression was not significantly different from the right V1 area of NC(P>0.05),and the difference of GABRR2/NMDAR1 between the right V1 area of MFD and the right V1 area of NC was statistically significant(P<0.05).Conclusion:1.Form-deprived amblyopia(FDA)in guinea pigs was developed within 1 week of form deprivation,while form-deprived myopia(FDM)was established between 1 and4 weeks of form deprivation.The visual acuity abnormalities caused by form deprivation may precede the increase of axial length and the decrease of diopter.From 4 to 8 weeks of form deprivation,FDA and FDM co-exist in guinea pigs.This animal model has important implications for further studies on the pathogenesis of myopic amblyopia.2.As an abnormal visual stimulus,form deprivation could significantly upregulate the expression of NMDAR1 and GABRR2 in the retinas of guinea pig form-deprived eyes.The ratio of GABRR2 to NMDAR1 in form-deprived eyes was also significantly higher than that in the other two eyes.The imbalance of inhibitory and excitatory signals may affect the plasticity of retinal neurons and cause abnormal eye development;however,the relevant specific mechanisms still need to be further investigated.3.Form deprivation can cause changes in NMDAR1 and GABRR2 expression not only in the retina of form-deprived eyes,but also in the V1 area corresponding to the form-deprived eyes,which suggested that other effects caused by monocular deprivation should be taken into account when conducting the basic myopia.Different from the increased expression of NMDAR1 in the retina of form-deprived eyes,the expression of NMDAR1 in the corresponding V1 areas of form-deprived eyes decreased,indicating that although myopia and amblyopia co-existed after long-term monocular form deprivation,but the different expression of NMDAR1 in the retina and visual cortex,to some extent,showed that the mechanisms of myopia and amblyopia are different.In addition,the expression of NMDAR1 in the V1 areas of the contralateral eye showed a similar trend to that of the deprived eye,which verified that the non-deprived eye of MFD may also have visual defects to a certain extent. |
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