Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York, USA.
Nat Neurosci. 2013 Aug;16(8):1049-59. doi: 10.1038/nn.3461. Epub 2013 Jul 14.
NMDA receptors (NMDARs) are classically known as coincidence detectors for the induction of long-term synaptic plasticity and have been implicated in hippocampal CA3 cell-dependent spatial memory functions that likely rely on dynamic cellular ensemble encoding of space. The unique functional properties of both NMDARs and mossy fiber projections to CA3 pyramidal cells place mossy fiber NMDARs in a prime position to influence CA3 ensemble dynamics. By mimicking presynaptic and postsynaptic activity patterns observed in vivo, we found a burst timing-dependent pattern of activity that triggered bidirectional long-term NMDAR plasticity at mossy fiber-CA3 synapses in rat hippocampal slices. This form of plasticity imparts bimodal control of mossy fiber-driven CA3 burst firing and spike temporal fidelity. Moreover, we found that mossy fiber NMDARs mediate heterosynaptic metaplasticity between mossy fiber and associational-commissural synapses. Thus, bidirectional NMDAR plasticity at mossy fiber-CA3 synapses could substantially contribute to the formation, storage and recall of CA3 cell assembly patterns.
N-甲基-D-天冬氨酸受体（NMDARs）通常被认为是长时程突触可塑性诱导的巧合探测器，并且已经涉及到海马 CA3 细胞依赖性空间记忆功能，这些功能可能依赖于空间的动态细胞集合编码。NMDAR 和苔藓纤维投射到 CA3 锥体细胞的独特功能特性使苔藓纤维 NMDAR 处于影响 CA3 集合动力学的最佳位置。通过模拟体内观察到的突触前和突触后活动模式，我们发现了一种爆发时间依赖性的活动模式，这种模式在大鼠海马切片中的苔藓纤维-CA3 突触处触发了双向长时 NMDAR 可塑性。这种形式的可塑性赋予了苔藓纤维驱动的 CA3 爆发发射和尖峰时间保真度的双峰控制。此外，我们发现苔藓纤维 NMDAR 介导了苔藓纤维和联合-联络突触之间的异突触代谢可塑性。因此，苔藓纤维-CA3 突触处的双向 NMDAR 可塑性可能对 CA3 细胞集合模式的形成、存储和回忆有重要贡献。
