Cellular Function Research Center, Yanbian University, Yanji, Jilin Province, China.
PLoS One. 2012;7(5):e37031. doi: 10.1371/journal.pone.0037031. Epub 2012 May 18.
Cerebellar cortical molecular layer interneurons (MLIs) play essential roles in sensory information processing by the cerebellar cortex. However, recent experimental and modeling results are questioning traditional roles for molecular layer inhibition in the cerebellum.
Synaptic responses of MLIs and Purkinje cells (PCs), evoked by air-puff stimulation of the ipsilateral whisker pad were recorded from cerebellar cortex Crus II in urethane-anesthetized ICR mice by in vivo whole-cell patch-clamp recording techniques. Under current-clamp (I = 0), air-puff stimuli were found to primarily produce inhibition in PCs. In MLIs, this stimulus evoked spike firing regardless of whether they made basket-type synaptic connections or not. However, MLIs not making basket-type synaptic connections had higher rates of background activity and also generated spontaneous spike-lets. Under voltage-clamp conditions, excitatory postsynaptic currents (EPSCs) were recorded in MLIs, although the predominant response of recorded PCs was an inhibitory postsynaptic potential (IPSP). The latencies of EPSCs were similar for all MLIs, but the time course and amplitude of EPSCs varied with depth in the molecular layer. The highest amplitude, shortest duration EPSCs were recorded from MLIs deep in the molecular layer, which also made basket-type synaptic connections. Comparing MLI to PC responses, time to peak of PC IPSP was significantly slower than MLI recorded EPSCs. Blocking GABA(A) receptors uncovered larger EPSCs in PCs whose time to peak, half-width and 10-90% rising time were also significantly slower than in MLIs. Biocytin labeling indicated that the MLIs (but not PCs) are dye-coupled.
These findings indicate that tactile face stimulation evokes rapid excitation in MLIs and inhibition occurring at later latencies in PCs in mouse cerebellar cortex Crus II. These results support previous suggestions that the lack of parallel fiber driven PC activity is due to the effect of MLI inhibition.
小脑皮质分子层中间神经元（MLIs）在小脑皮质的感觉信息处理中发挥着重要作用。然而，最近的实验和建模结果对分子层抑制在小脑中的传统作用提出了质疑。
在乌拉坦麻醉的 ICR 小鼠的小脑皮层 Crus II 中，通过体内全细胞膜片钳记录技术，记录了由同侧触须垫空气喷射刺激诱发的 MLIs 和浦肯野细胞（PCs）的突触反应。在电流钳（I = 0）下，空气喷射刺激主要在 PCs 中产生抑制。在 MLIs 中，无论它们是否形成篮状突触连接，这种刺激都会诱发尖峰放电。然而，不形成篮状突触连接的 MLIs 具有更高的背景活动率，并且也会产生自发的尖峰。在电压钳条件下，在 MLIs 中记录到兴奋性突触后电流（EPSCs），尽管记录的 PCs 的主要反应是抑制性突触后电位（IPSP）。所有 MLIs 的 EPSC 潜伏期相似，但 EPSC 的时间过程和幅度随分子层深度而变化。在分子层较深的 MLIs 中记录到最高幅度、最短持续时间的 EPSC，这些 MLIs 也形成篮状突触连接。将 MLI 与 PC 反应进行比较，PC IPSP 的峰值时间明显慢于 MLI 记录的 EPSCs。阻断 GABA(A)受体后，PC 中记录到更大的 EPSCs，其峰值时间、半宽度和 10-90%上升时间也明显慢于 MLIs。生物胞素标记表明 MLIs（而不是 PCs）是染料偶联的。
这些发现表明，触须刺激在小鼠小脑皮层 Crus II 中迅速兴奋 MLIs，并在稍后的潜伏期在 PCs 中产生抑制。这些结果支持先前的建议，即缺乏平行纤维驱动的 PC 活动是由于 MLI 抑制的影响。
