Voronin L L, Rossokhin A V, Sokolov M V
Science Research Institute of the Brain, Russian Academy of Medical Sciences, Moscow.
Neurosci Behav Physiol. 1999 May-Jun;29(3):347-54. doi: 10.1007/BF02465348.
The mechanisms of the early (up to 1 h) and late (up to 3 h) phases of long-term potentiation were studied by analyzing the interaction between long-term potentiation and presynaptic paired-pulse facilitation. "Minimal" excitatory postsynaptic potentials were measured in pyramidal neurons in field CA1 of rat hippocampal slices in conditions of paired-pulse stimulation of the radial layer. In most neurons, paired-pulse facilitation decreased after induction of long-term potentiation, and this reduction lasted throughout the recording period (up to 3.5 h). Changes in paired-pulse facilitation correlated with the extent of long-term facilitation and with the initial level of paired-pulse facilitation, and the extent of facilitation depended on the initial level of paired-pulse facilitation. This latter relationship was different for the early and late phases of long-term potentiation and increased with time. Overall, the data obtained here demonstrate a significant role for presynaptic mechanisms in maintaining both the early and late phases of long-term potentiation. It is suggested that the basic mechanism of the early phase of potentiation is an increase in the probability that transmitter will be released, which also leads to an increase in the number of effective release sites, due to transformation of "presynaptically quiet" synapses into effective synapses. It is proposed that the development of the late phase is based on simultaneous pre- and postsynaptic structural transformations which increase the number of synaptically active zones.
通过分析长时程增强（LTP）与突触前配对脉冲易化之间的相互作用，研究了长时程增强早期（长达1小时）和晚期（长达3小时）阶段的机制。在大鼠海马切片CA1区锥体细胞中，在对放射层进行配对脉冲刺激的条件下，测量“最小”兴奋性突触后电位。在大多数神经元中，长时程增强诱导后配对脉冲易化降低，且这种降低在整个记录期（长达3.5小时）持续存在。配对脉冲易化的变化与长时程易化的程度以及配对脉冲易化的初始水平相关，并且易化程度取决于配对脉冲易化的初始水平。长时程增强的早期和晚期阶段这种后一种关系有所不同，且随时间增加。总体而言，此处获得的数据表明突触前机制在维持长时程增强的早期和晚期阶段均发挥重要作用。研究表明，增强早期阶段的基本机制是递质释放概率增加，这也导致有效释放位点数量增加，这是由于“突触前静息”突触转变为有效突触所致。有人提出，晚期阶段的发展基于突触前和突触后同时发生的结构转变，这些转变增加了突触活性区的数量。
