| Objective To investigate the changes of temporal window of spike-timing dependent plasticity and the underlying mechanism in the V1 B area of mice monocular deprived visual cortex.Method Healthy C57BL/6 mice of either sex were randomly divided into:(1) normal control group(P 24)(2) monocular deprivation group: right eye was sutured three days(P24). The visual cortex was cut into 400μM brain slices. Visualized whole-cell current-clamp recordings were made from layer Ⅱ/Ⅲ regular-spiking pyramidal cells of primary visual cortex in normal Reared and monocular deprivied mice(including deprived side or non-deprived side) to record excitatory postsynaptic potential(EPSP) and excitatory postsynaptic current(EPSC). LTP and LTD were induced by STDP protocol.p Clamp 10(Molecular devices, LLC) software are applicated for data acquisition, analysis and graphing. SPSS11.0 statistical software are used for statistical analysis, and measurement data using a unified expressed as mean ± standard error.Results 1 The changes of STDP timing window in primary visual cortex of normal reared mice.(1)In cells from normal reared(NR) mice the pre- then post- pairing resulted in t LTP when the delay was 10 ms(EPSP slope 124.1±3.9%; n=9,7) but not when it was 100 ms(EPSP slope 100.4±3.3%, n=8,7; p<0.001).(2)In cells from normal reared(NR) mice the post- then pre- pairing resulted in t LTD when the delay was 10 ms(EPSP slope 76.5±3.5%, n=9,7) but not when it was 100 ms(EPSP slope 101.2±1.5%, n=10,7; p<0.001).(3)The summary results showed that timing window of STDP of primary visual cortex form normal mice was-100 ms ~ + 50 ms.2. The changes of STDP timing window in monocular deprivied mice.2.1 The changes of STDP timing window from contrallateral visual cortex.(deprived side).(1)In cells from monocular deprived visual cortex both delays resulted in comparable t LTP( Δt =+10ms: EPSP slope 130.8±1.7%,n=8,5; Δt =+100ms: EPSP slope 114.7±0.3%,n=7,5;P<0.001).(2)In cells from monocular deprived visual cortex both delays resulted in comparable t LTD( Δt =-10ms:74.8±0.77%,n=8,5; Δt =-100ms:92.5±0.67%,n=7,5;P<0.001).(3) STDP timing window in cells from monocular deprived visual cortex was-200 ms ~ + 200 ms.2.2 The changes of STDP timing window in cells from ipsilatral cortex(non-deprived visual cortex)(1)In contrast, in non-deprived visual cortex, the pre- then post- pairing resulted in t LTP when the delay was 10 ms and 50ms(Δt=+10ms: EPSP slope 129.6±1.5%,n=8,5; Δt=+50ms:EPSP slope120.5±0.9%,n=8,5), but not when it was 100ms(Δt=+100ms: EPSP slope 101.1±0.6%,n=7,5).(2)In non-deprived visual cortex, the post- then prepairing resulted in t LTD when the delay was 10 ms, but not when it was 100ms(Δt=-10ms:79.8±0.79%,n=8,5; Δt=-100 ms : 99.6±0.89%,n=8,5).(3) STDP timing window in cells from non-deprived visual cortex was-100 ms ~ + 100 ms.3 The mechanism underlying the changes of STDP integration window during the critical period in which right eyes of mice were sutured for 3 days.After 3-day monocular deprivation, the decay duration of NMDAR-EPSC was longer than the normal reared group(τw: MD: 149.10 ± 7.3 n = 8,4; NR: 99.9 ± 6.8 n = 8,4). Monocular deprivation prolonged and increased duration and amplitute of NMDAR-EPSCs,which became more sensive to ifenprodil.(τw:MD:93.59±3.11 n=8,4;NR:89.23±3.9 n=8,4;.Amplitute MD58.1 ± 3.5 n = 8,4; NR: 31.6 ± 3.9 n = 8,4).Conclusion 1.monocular deprivation extended the integration window of contallatral visual cortex(deprived side).However, there was little changes of non-depived side;2. The mechanism of the changes of STDP timing window was the prolonged duration of NMDAR response which was associated with the relative increased level of NR2B... |
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