Dudek S M, Friedlander M J
Neurobiology Research Center, University of Alabama at Birmingham, 35294-0021, USA.
Neuron. 1996 Jun;16(6):1097-106. doi: 10.1016/s0896-6273(00)80136-1.
For in vitro LTD to remain viable as a model for synaptic weakening in visual cortical plasticity, it is crucial that it display a critical period for its induction within layer IV. A complicating factor, however, is that LTD in layer IV is modulated by inhibitory postsynaptic potentials (IPSPs); postsynaptic responses characterized as containing IPSPs do not depress in response to 1 Hz afferent stimulation. By blocking IPSPs intracellularly, we find that the ability to induce LTD in layer IV neurons is restored in juvenile, but not in mature animals. This developmental down-regulation of LTD induction is specific for layer IV when compared with LTD induction in layers II/III. These data are consistent with the hypothesis that an LTD-like phenomenon is involved in critical period plasticity and is apparently independent of developmental changes in inhibitory circuitry.
为使体外长时程抑制（LTD）作为视觉皮层可塑性中突触减弱的模型保持可行性，至关重要的是它要在IV层内显示出诱导的关键期。然而，一个复杂因素是IV层中的LTD受抑制性突触后电位（IPSPs）调节；被表征为包含IPSPs的突触后反应在1 Hz传入刺激下不会减弱。通过细胞内阻断IPSPs，我们发现诱导IV层神经元中LTD的能力在幼年动物中得以恢复，但在成年动物中则不然。与II/III层中的LTD诱导相比，LTD诱导的这种发育性下调在IV层中是特异性的。这些数据与以下假设一致，即类似LTD的现象参与关键期可塑性，并且显然独立于抑制性神经回路的发育变化。
