Enhanced visual activity in vivo forms nascent synapses in the developing retinotectal projection
Enhanced visual activity in vivo forms nascent synapses in the developing retinotectal projection
复制标题
DOI：
10.1152/jn.00452.2006
复制
发表时间：
2007-04-01
影响因子：
2.5
通讯作者：
Cline, Hollis T.
中科院分区：
文献类型：
--
作者：
Aizenman, Carlos D.;Cline, Hollis T.
发育过程中的神经活动模式对于感觉回路的正确布线至关重要。以前的工作表明，暴露自由游泳爪蟾蝌蚪4小时的增强视觉刺激加速视顶盖神经元在体内的树突状生长速度。在这里，我们测试是否这同一时期的视觉刺激增加突触的成熟和形成新的突触在retinotectal途径。我们评估了48期蝌蚪暴露于模拟运动刺激4-5小时的突触特性。基于我们的研究结果，即与更成熟的突触相比，未成熟的视网膜顶盖突触具有更大的成对脉冲易化，与较低的释放概率（Pr）一致，我们使用成对脉冲方案选择性地从具有低Pr的新生突触中引发反应。尽管对照蝌蚪中单个和成对刺激的AMPA/NMDA比率相同，视觉刺激引起配对反应的AMPA/NMDA比率的相对降低。我们诱发视网膜顶盖突触传递的存在下，Sr 2+记录异步囊泡释放。我们比较了由单一和成对刺激诱导的诱发mEPSC，发现视觉刺激选择性地增强由成对刺激诱发的AMPA受体（AMPAR）介导的mEPSC的幅度和数量。总之，这些结果表明，增强的视觉刺激会影响成对脉冲刺激揭示的突触群体中AMPAR和NMDAR介导的反应。这表明，在体内的视觉刺激增加突触，具有低Pr，并具有与不成熟的突触一致的属性。
Patterned neural activity during development is critical for proper wiring of sensory circuits. Previous work demonstrated that exposing freely swimming Xenopus tadpoles to 4 h of enhanced visual stimulation accelerates the dendritic growth rate of optic tectal neurons in vivo. Here we test whether this same period of visual stimulation increased synaptic maturation and formation of new synapses in the retinotectal pathway. We assessed synaptic properties of stage 48 tadpoles that were exposed to a simulated-motion stimulus for 4-5 h. Based on our findings that immature retinotectal synapses have greater paired-pulse facilitation compared with more mature synapses, consistent with a lower release probability (Pr), we used a paired-pulse protocol to elicit responses selectively from nascent synapses with low Pr. Although AMPA/NMDA ratios for single and paired stimuli were the same in control tadpoles, visual stimulation caused a relative decrease in the AMPA/NMDA ratio of the paired response. We evoked retinotectal synaptic transmission in the presence of Sr2+ to record asynchronous vesicle release. We compared evoked mEPSCs induced by single and paired stimuli and found that visual stimulation selectively enhances the amplitude and number of AMPA receptor (AMPAR)-mediated mEPSCs evoked by paired stimuli relative to those evoked by single stimuli. Together these results show that enhanced visual stimulation affects both AMPAR- and NMDAR-mediated responses in a population of synapses revealed by paired-pulse stimulation. This suggests that in vivo visual stimulation increases synapses that have a low Pr and that have properties consistent with immature synapses.