J. C. Rekling: Department of Neuroscience and Pharmacology, Copenhagen University - Panum Institute - 12.3, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark.
J Physiol. 2014 Jan 1;592(1):33-47. doi: 10.1113/jphysiol.2013.260067. Epub 2013 Sep 16.
The inferior olivary nucleus (IO) in in vitro slices from postnatal mice (P5.5-P15.5) spontaneously generates clusters of neurons with synchronous calcium transients, and intracellular recordings from IO neurons suggest that electrical coupling between neighbouring IO neurons may serve as a synchronizing mechanism. Here, we studied the cluster-forming mechanism and find that clusters overlap extensively with an overlap distribution that resembles the distribution for a random overlap model. The average somatodendritic field size of single curly IO neurons was ∼6400 μm(2), which is slightly smaller than the average IO cluster size. Eighty-seven neurons with overlapping dendrites were estimated to be contained in the principal olive mean cluster size, and about six non-overlapping curly IO neurons could be contained within the largest clusters. Clusters could also be induced by iontophoresis with glutamate. Induced clusters were inhibited by tetrodotoxin, carbenoxelone and 18β-glycyrrhetinic acid, suggesting that sodium action potentials and electrical coupling are involved in glutamate-induced cluster formation, which could also be induced by activation of N-methyl-d-aspartate and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors. Spikelets and a small transient depolarizing response were observed during glutamate-induced cluster formation. Calcium transients spread with decreasing velocity during cluster formation, and somatic action potentials and cluster formation are accompanied by large dendritic calcium transients. In conclusion, cluster formation depends on gap junctions, sodium action potentials and spontaneous clusters occur randomly throughout the IO. The relative slow signal spread during cluster formation, combined with a strong dendritic influx of calcium, may signify that active dendritic properties contribute to cluster formation.
橄榄下核（IO）在出生后第 5.5 天至第 15.5 天的离体切片中自发产生具有同步钙瞬变的神经元簇，并且 IO 神经元的细胞内记录表明，相邻 IO 神经元之间的电耦合可能作为一种同步机制。在这里，我们研究了簇形成机制，发现簇广泛重叠，重叠分布类似于随机重叠模型的分布。单个卷曲 IO 神经元的平均体树突场大小约为 6400 μm(2)，略小于平均 IO 簇大小。估计有 87 个具有重叠树突的神经元包含在主橄榄平均簇大小中，并且大约六个不重叠的卷曲 IO 神经元可以包含在最大簇中。簇也可以通过谷氨酸的离子电泳诱导。诱导的簇被河豚毒素、卡贝酮和 18β-甘草次酸抑制，表明钠离子动作电位和电耦合参与谷氨酸诱导的簇形成，这也可以通过激活 N-甲基-D-天冬氨酸和 α-氨基-3-羟基-5-甲基-4-异恶唑丙酸受体来诱导。在谷氨酸诱导的簇形成过程中观察到棘波和短暂的去极化反应。钙瞬变在簇形成过程中以降低的速度传播，并且动作电位和簇形成伴随着大的树突钙瞬变。总之，簇形成取决于缝隙连接，钠离子动作电位和自发性簇在整个 IO 中随机发生。簇形成过程中信号传播相对较慢，加上钙在树突中的大量内流，可能表明活性树突特性有助于簇形成。
