中文摘要：

本研究采用膜片钳全细胞记录的方法研究了Sprague-Dawley（SD）大鼠初级视皮层第Ⅱ/Ⅲ层内部侧向突触联系可塑性发育变化的动态过程。采用Pairing Stimulation的方法,分别在初级视皮层第Ⅱ/Ⅲ层和第IV层对位于第Ⅱ/Ⅲ层的神经元进行长时程增强（long term potentiation,LTP）效应的诱导,并记录结果。结果显示：（1）SD大鼠神经元第Ⅱ/Ⅲ层神经元在第Ⅱ/Ⅲ层到第Ⅱ/Ⅲ层的水平方向和第IV层到第Ⅱ/Ⅲ层的垂直方向可分别独立诱导出突触后兴奋性电流;（2）SD大鼠初级视皮层第Ⅱ/Ⅲ层之间侧向联系的LTP在出生后第12天（睁眼）之前可以被水平强直刺激诱导;（3）SD大鼠初级视皮层第Ⅱ/Ⅲ层兴奋性神经元在睁眼前,水平方向的强直刺激只能诱导出从第IV层到第Ⅱ/Ⅲ层突触反应短时程增强;（4）大鼠眼睁开（P12）后,水平方向的强直刺激可诱导出第IV层到第Ⅱ/Ⅲ层间突触联系的LTP;（5）在大鼠出生后第14天,当接连给予垂直方向和水平方向的强直刺激,水平方向的强直刺激使得垂直方向强直刺激诱发出的从第IV层到第Ⅱ/Ⅲ层突触联系LTP幅度下降。这一结果提示：当两个方向的强直刺激同时给予的时候,水平输入对于垂直输入在垂直突触联系上调控有削弱的作用;（6）SD大鼠初级视皮层第Ⅱ/Ⅲ层兴奋性神经元突触AMPA受体自发反应受发育调控。在眼睁开前,AMPA受体自发反应的频率较低,在出生后第12～14天内急剧上升,而在出生后第18天后略有下降。AMPA受体自发反应的幅度在出生后第12天后略有下降。以上结果揭示,水平方向的突触联系强度和水平方向的输入对垂直方向的突触联系的作用都受到发育调控。第Ⅱ/Ⅲ层内部水平输入对于垂直方向的输入具有双重作用,这种相互作用可能涉及神经网络形成过程中竞争机制,也可能涉及视觉功能柱的形成。

英文摘要：

In the present research, patch-clamp whole-cell recording was used to study the developmental changes of the internal horizontal synaptic plasticity in layer Ⅱ/Ⅲ of rats＇ primary visual cortices. Pairing stimulation was used to induce long term potentiation （LTP） of neurons in layer Ⅱ/Ⅲ from layer Ⅱ/Ⅲ and layer IV. The data indicate that： （1） Responses of layer II/III neurons can be evoked independently at Ⅱ/Ⅲ-Ⅱ/Ⅲ and IV-Ⅱ/Ⅲ synapses by horizontal and vertical stimulations; （2） LTP can be induced from neurons in the layer Ⅱ/Ⅲ by horizontal tetanic stimulation at Ⅱ/Ⅲ-Ⅱ/Ⅲsynapses till postnatal day12 （P12, before eyes open）; （3） Meanwhile, only short term potentiation （STP） at Ⅳ-Ⅱ/Ⅲ synapses can be induced by horizontal tetanic stimulation before eyes open; （4） After P12, a robust LTP at Ⅳ-Ⅱ/Ⅲ synapses can be induced by horizontal tetanic stimulation; （5） At P14, when vertical and horizontal tetanic stimulations were given to the same neuron, the LTP at IV-Ⅱ/Ⅲ synapses was weaker than that induced by vertical stimulation alone, suggesting that vertical Synaptic modification was negatively regulated by horizontal inputs when two-direction synaptic inputs were presented at the same time; （6） Spontaneous responses of AMPA receptors （AMPARs） in the layer Ⅱ/Ⅲ neuron of rats＇ primary visual cortices are regulated by the development. The frequency of AMPARs-mediated postsynaptic currents was at a low level before eyes open, increased sharply at P12-P14, and slightly decreased after P18. And the amplitude of spontaneous AMPARs currents slowly decreased after P12. The results demonstrated that both the strength of horizontal synaptic modification and the effects of horizontal inputs on the vertical synaptic connection are regulated by the development. Ⅱ/Ⅲ-Ⅱ/Ⅲ synaptic communication has dual effects on the Ⅳ-Ⅱ/Ⅲ synapses, which may be involved in a competitive machinery of neural circuitry maturation and the fo