Lamsa Karri, Heeroma Joost H, Kullmann Dimitri M
Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK.
Nat Neurosci. 2005 Jul;8(7):916-24. doi: 10.1038/nn1486.
Cortical information processing requires a delicate balance of excitatory and inhibitory signaling. How is this balance preserved during hippocampal memory encoding, which involves NMDA receptor-dependent long term potentiation (LTP)? This form of LTP occurs at synapses between pyramidal neurons but has not been detected in feed-forward inhibitory interneurons. We show that paired pre- and postsynaptic activity evokes pathway-specific LTP in half of rat stratum radiatum interneurons if cytoplasmic integrity is preserved. LTP occurs in aspiny feed-forward interneurons and propagates to pyramidal neurons as an enhancement of disynaptic inhibition. We also show that when LTP is restricted to synapses on pyramidal neurons, the temporal fidelity of synaptic integration and action potential generation in pyramidal cells is compromised. However, when LTP also occurs at synapses on feed-forward interneurons, temporal fidelity is preserved. We propose that Hebbian LTP at synapses driving disynaptic inhibition is necessary to maintain information processing without degradation during memory encoding.
皮质信息处理需要兴奋性和抑制性信号之间的微妙平衡。在涉及NMDA受体依赖性长时程增强（LTP）的海马记忆编码过程中，这种平衡是如何维持的呢？这种形式的LTP发生在锥体神经元之间的突触处，但在前馈抑制性中间神经元中尚未检测到。我们发现，如果细胞质完整性得以保留，成对的突触前和突触后活动会在一半的大鼠辐射层中间神经元中诱发通路特异性LTP。LTP发生在无棘前馈中间神经元中，并作为双突触抑制的增强传播到锥体神经元。我们还表明，当LTP仅限于锥体神经元上的突触时，锥体细胞中突触整合和动作电位产生的时间保真度会受到损害。然而，当LTP也发生在前馈中间神经元的突触时，时间保真度得以保留。我们提出，驱动双突触抑制的突触处的赫布型LTP对于在记忆编码过程中维持信息处理而不退化是必要的。
