Enoki Ryosuke, Hu Yi-Ling, Hamilton David, Fine Alan
Neuroscience Institute and Department of Physiology & Biophysics, Dalhousie University, Halifax, NS B3H1X5, Canada.
Neuron. 2009 Apr 30;62(2):242-53. doi: 10.1016/j.neuron.2009.02.026.
Key aspects of the expression of long-term potentiation (LTP) and long-term depression (LTD) remain unresolved despite decades of investigation. Alterations in postsynaptic glutamate receptors are believed to contribute to the expression of various forms of LTP and LTD, but the relative importance of presynaptic mechanisms is controversial. In addition, while aggregate synaptic input to a cell can undergo sequential and graded (incremental) LTP and LTD, it has been suggested that individual synapses may only support binary changes between initial and modified levels of strength. We have addressed these issues by combining electrophysiological methods with two-photon optical quantal analysis of plasticity at individual active (non-silent) Schaffer collateral synapses on CA1 pyramidal neurons in acute slices of hippocampus from adolescent rats. We find that these synapses sustain graded, bidirectional long-term plasticity. Remarkably, changes in potency are small and insignificant; long-term plasticity at these synapses is expressed overwhelmingly via presynaptic changes in reliability of transmitter release.
尽管经过数十年的研究，长时程增强（LTP）和长时程抑制（LTD）表达的关键方面仍未得到解决。突触后谷氨酸受体的改变被认为有助于各种形式的LTP和LTD的表达，但突触前机制的相对重要性存在争议。此外，虽然细胞的总体突触输入可以经历连续和分级（增量）的LTP和LTD，但有人提出单个突触可能仅支持强度初始水平和改变水平之间的二元变化。我们通过将电生理方法与对来自青春期大鼠海马急性切片中CA1锥体神经元上单个活跃（非沉默）的Schaffer侧支突触的可塑性进行双光子光学量子分析相结合，解决了这些问题。我们发现这些突触维持分级、双向的长期可塑性。值得注意的是，效能变化很小且不显著；这些突触的长期可塑性主要通过递质释放可靠性的突触前变化来表达。
