Synaptic basis for whisker deprivation- induced synaptic depression in rat somatosensory cortex
Synaptic basis for whisker deprivation- induced synaptic depression in rat somatosensory cortex
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DOI：
10.1523/jneurosci.0175-06.2006
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发表时间：
2006-04-19
影响因子：
5.3
通讯作者：
Feldman, DE
中科院分区：
文献类型：
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作者：
Bender, KJ;Allen, CB;Feldman, DE
胡须剥夺减弱了大鼠初级躯体感觉(S1)皮层L2/3锥体细胞的兴奋性第四层(L4)传入，这可能与胡须MAP的可塑性有关。这种减弱被认为是体内感觉剥夺引起的长期抑郁(LTD)。在这里，我们研究了剥夺诱导L4-L2/3输入减弱的突触表达机制，并评估了它与L4-L2/3突触前表达的LTD的相似性。MK-801[(5S，10R)-(+)-5-甲基-10，11-二氢-5H-二苯并[a，d]环庚烯-5，10-亚胺马来酸]可使L4-L2/3突触的成对脉冲比率增加，并减缓对NMDA受体电流的依赖阻断，表明剥夺这些突触的递质释放几率降低。相反，剥夺既没有改变L2/3神经元的微小EPSC幅度，也没有改变用锶测量的L4-L2/3定量突触反应的幅度，表明突触后反应没有变化。在出生后第12天(P12)的年轻大鼠中，至少需要4d的剥夺才能显著削弱L4-L2/3突触。当剥夺在较大年龄开始时(P20)，当突触大多成熟时，也会出现类似的减弱，这表明削弱不太可能代表突触成熟的失败，而是现有突触强度的降低。因此，胡须剥夺通过降低突触前功能来削弱L4-L2/3突触，类似于该突触的已知LTD机制。
Whisker deprivation weakens excitatory layer 4 (L4) inputs to L2/3 pyramidal cells in rat primary somatosensory (S1) cortex, which is likely to contribute to whisker map plasticity. This weakening has been proposed to represent long- term depression (LTD) induced by sensory deprivation in vivo. Here, we studied the synaptic expression mechanisms for deprivation- induced weakening of L4-L2/3 inputs and assessed its similarity to LTD, which is known to be expressed presynaptically at L4-L2/3 synapses. Whisker deprivation increased the paired pulse ratio at L4-L2/3 synapses and slowed the use- dependent block of NMDA receptor currents by MK- 801[(5S, 10R)-(+)-5methyl-10,11- dihydro-5H- dibenzo[a, d] cyclohepten-5,10- imine maleate], indicating that deprivation reduced transmitter release probability at these synapses. In contrast, deprivation did not alter either miniature EPSC amplitude in L2/3 neurons or the amplitude of quantal L4-L2/3 synaptic responses measured in strontium, indicating that postsynaptic responsiveness was unchanged. In young postnatal day 12 (P12) rats, at least 4 d of deprivation were required to significantly weaken L4-L2/3 synapses. Similar weakening occurred when deprivation began at older ages ( P20), when synapses are mostly mature, indicating that weakening is unlikely to represent a failure of synaptic maturation but instead represents a reduction in the strength of existing synapses. Thus, whisker deprivation weakens L4-L2/3 synapses by decreasing presynaptic function, similar to known LTD mechanisms at this synapse.