Homeostatic Synaptic Plasticity In Visual Development And Abnormal Visual Experiences Of Rats

ObjectivesTo measure mEPSCs in pyramidal cells in acuteⅡ/Ⅲlayer primary visual cortex slices in normal visual development before or/and within critical periods(between posmatal days 4 and 21).To evaluate homeostatic plasticity in abnormal visual environment and effect of natural herb A in synaptic level.Methods1.mEPSCs in normal visual development rats:P4-21 Wister rats were devided into posmatal 1 week(P4-11),2 weeks(P12-16)and 3 weeks(P17-21).Coronal brain slices of 400μm containing primary visual cortex were prepared,mEPSCs in pyramidal cells of layerⅡ/Ⅲof primary visual cortex were obtained by visualized whole-cell patch recording.Properties of mEPSCs were analyzed statistically by Clampfit 9.0 and SPSS for Windows 11.5.2.mEPSCs in monocular form-deprived(MFD)rats and reverse suture(RS)rats: MFD models were obtained in P14 Wister rats.mEPSCs recordings were made from bilateral visual cortex.For RS experiments,initial and control deprivations were performed without trimming the eyelids for 48h,to facilitate reopening for 48h. Recordings of mEPSCs were made from both hemispheres.3.mEPSCs with natural herb A:mEPSCs were obtained after natural herb A incubate perfusion on visual cortex slices of MFD rats and normal visual development rats.Results1.AMPA-mediated mEPSCs in normal visual development rats:within postnatal 1 week,amplitudes increased,frequency was lower;Rise and decay time tau decreased with age.We firstly recorded "single-channel-like" currents between P4 and P6.In postnatal 2 weeks,the amplitude of mEPSCs was decreased and frequency was increased with age.Within postnatal 3 weeks,properties of mEPSCs had no significant differences. 2.AMPA-mediated mEPSCs of MFD:Amplitude of mEPSCs in deprived and control primary visual cortex increased significantly,frequency decreased,and decay time tan delayed.Changes of mEPSCs reached the peak value at 2 days MFD(MFD2).In RS, amplitude of mEPSCs in initial deprived cortex decreased,frequency increased and decay time tau delayed.Amplitude of mEPSCs in RS side increased,frequency decreased,and rise time tau and/or decay time tau reduced than deprived and control cortex but normal cortex.3.MFD with natural herb A:AMPA-mediated mEPSCs in deprived primary visual cortex was changed by natural herb A.Those were amplitude decreasing,frequency increasing and decay time tau reducing.In control side,there were only amplitude decrease and frequency increasing slightly.There were no effects of mEPSCs on normal visual development rats by natural herb A.Conclusions1.For normal visual development rats,synaptic homeostatic plasticity in primary visual cortex is not mature before eyes open,down-scaling after eyes open,and then keep steady.2.MFD can lead up-scaling of synaptic homeostatic plasticity in deprived primary visual cortex.In the control visual cortex,there are slightly up-scaling.Efficiency of deprivation reaches the peak value after monocular eyelid suture 2 days.RS can partially ameliorate the deprivation efficiency of deprived visual cortex,but can not reach the normal level.Synaptic homeostatic plasticity in primary visual cortex of RS is mildly up-scaled.3.Natural herb A can lead up-scaling of synaptic homeostatic plasticity in MFD presynapticly and postsynapticly,and has no effects on normal rats.