Post-tetanic potentiation (PTP) is an attractive candidate mechanism for hippocampus-dependent short-term memory. Although PTP has a uniquely large magnitude at hippocampal mossy fiber-CA3 pyramidal neuron synapses, it is unclear whether it can be induced by natural activity and whether its lifetime is sufficient to support short-term memory. We combined in vivo recordings from granule cells (GCs), in vitro paired recordings from mossy fiber terminals and postsynaptic CA3 neurons, and “flash and freeze” electron microscopy. PTP was induced at single synapses and showed a low induction threshold adapted to sparse GC activity in vivo. PTP was mainly generated by enlargement of the readily releasable pool of synaptic vesicles, allowing multiplicative interaction with other plasticity forms. PTP was associated with an increase in the docked vesicle pool, suggesting formation of structural “pool engrams.” Absence of presynaptic activity extended the lifetime of the potentiation, enabling prolonged information storage in the hippocampal network.

强直后增强（PTP）是海马依赖性短期记忆的一种有吸引力的候选机制。尽管PTP在海马苔藓纤维-CA3锥体神经突触中具有独特的大小，但尚不清楚它是否可以由自然活动诱导，其寿命是否足以支持短期记忆。我们结合了颗粒细胞（GCs）的体内记录，苔藓纤维末端和突触后CA3神经元的体外配对记录，以及“闪烁和冷冻”电子显微镜。PTP在单个突触中被诱导，并显示出较低的诱导阈值，适于体内稀疏的GC活性。PTP主要是通过扩大易释放的突触小泡池而产生的，从而允许与其他可塑性形式的倍增相互作用。PTP与停泊的囊泡池增加有关，表明形成了结构“池en”。突触前活动的缺乏延长了增强作用的寿命，从而可以延长海马网络中的信息存储。