Institute of Zoology, Jagiellonian University, 30-060 Krakow, Poland.
J Neurosci. 2010 Jan 20;30(3):1176-84. doi: 10.1523/JNEUROSCI.2970-09.2010.
The structure of neurons changes during development and in response to injury or alteration in sensory experience. Changes occur in the number, shape, and dimensions of dendritic spines together with their synapses. However, precise data on these changes in response to learning are sparse. Here, we show using quantitative transmission electron microscopy that a simple form of learning involving mystacial vibrissae results in approximately 70% increase in the density of inhibitory synapses on spines of neurons located in layer IV barrels that represent the stimulated vibrissae. The spines contain one asymmetrical (excitatory) and one symmetrical (inhibitory) synapse (double-synapse spines), and their density increases threefold as a result of learning with no apparent change in the density of asymmetrical synapses. This effect seems to be specific for learning because pseudoconditioning (in which the conditioned and unconditioned stimuli are delivered at random) does not lead to the enhancement of symmetrical synapses but instead results in an upregulation of asymmetrical synapses on spines. Symmetrical synapses of cells located in barrels receiving the conditioned stimulus also show a greater concentration of GABA in their presynaptic terminals. These results indicate that the immediate effect of classical conditioning in the "conditioned" barrels is rapid, pronounced, and inhibitory.
神经元的结构在发育过程中以及对损伤或感觉经验改变的反应中会发生变化。树突棘及其突触的数量、形状和尺寸都会发生变化。然而，关于学习引起的这些变化的确切数据还很稀少。在这里，我们使用定量透射电子显微镜表明，一种简单的学习形式涉及须动，导致代表被刺激的触须的 IV 层桶状神经元的棘突上的抑制性突触密度增加约 70%。这些棘突包含一个不对称（兴奋性）和一个对称（抑制性）突触（双突触棘突），并且由于学习，它们的密度增加了三倍，而不对称突触的密度没有明显变化。这种效应似乎是特定于学习的，因为伪条件作用（其中条件和非条件刺激是随机提供的）不会导致对称突触的增强，而是导致接受条件刺激的桶状接收细胞的棘突上的不对称突触的上调。位于接收条件刺激的桶状细胞中的对称突触的突触前末端也显示出 GABA 的浓度更高。这些结果表明，经典条件作用在“条件”桶中的即时效应是快速、显著和抑制性的。
