Sjöström Per Jesper, Turrigiano Gina G, Nelson Sacha B
Department of Biology and Center for Behavioral Genomics, Brandeis University, Waltham, MA 02454, USA.
Neuropharmacology. 2007 Jan;52(1):176-84. doi: 10.1016/j.neuropharm.2006.07.021. Epub 2006 Aug 8.
Long-term potentiation and depression (LTP and LTD) are cellular plasticity phenomena expressed at a variety of central synapses, and are thought to contribute to learning and developmental changes in circuitry. Recurrent neocortical layer-5 synapses are thought to express a presynaptic form of LTP that influences the short-term plasticity of the synapse. Here we show that changes in synaptic strength elicited by pairing high frequency pre- and postsynaptic firing at this synapse result from a mixture of presynaptic and postsynaptic forms of plasticity, as assessed by the analysis of changes in coefficient of variation, short-term plasticity, and NMDA:AMPA current ratios. Pharmacological dissection of this plasticity revealed that block of presynaptic LTD with an endocannabinoid inhibitor enhanced LTP, while the apparently presynaptic component of LTP could be prevented by induction in the presence of blockers of nitric oxide. These data suggest that correlated high-frequency firing at layer-5 synapses simultaneously induces a mixture of presynaptic LTD, presynaptic LTP, and postsynaptic LTP.
长时程增强和抑制（LTP和LTD）是在各种中枢突触中表现出的细胞可塑性现象，被认为有助于学习和神经回路的发育变化。人们认为，新皮层第5层的递归突触表达一种突触前形式的LTP，它会影响突触的短期可塑性。在这里，我们表明，通过配对该突触处的高频突触前和突触后放电所引发的突触强度变化，是由突触前和突触后可塑性形式混合产生的，这是通过对变异系数、短期可塑性和NMDA:AMPA电流比率变化的分析来评估的。对这种可塑性的药理学剖析表明，用内源性大麻素抑制剂阻断突触前LTD可增强LTP，而在一氧化氮阻滞剂存在的情况下诱导LTP时，LTP的明显突触前成分可被阻止。这些数据表明，第5层突触处的相关高频放电同时诱导了突触前LTD、突触前LTP和突触后LTP 的混合。
