Kalia M, Schweitzer P, Champagnat J, Denavit-Saubie M
Department of Neurosurgery, Thomas Jefferson University, Philadelphia, Pennsylvania 19107-6799.
J Comp Neurol. 1993 Jan 1;327(1):37-47. doi: 10.1002/cne.903270104.
We have used electrophysiology and light microscopy of intracellularly labeled neurons in the nucleus of the tractus solitarius (nTS) in brainstem slices of the newborn rat (P0 to P6) to examine the functional and morphological correlation of their development. Three-dimensional reconstruction of neurons injected intracellularly with biocytin, following electrophysiological recording, revealed a close correspondence between morphological immaturity (appearing as polarization of the dendritic tree) and the absence of a ramp-like voltage trajectory at the offset of hyperpolarizing current injections-IA negativity (8 of the 8 cells examined showed this correlation). These morphologically polarized IA negative neurons showed preferential dendritic sprouting in two diametrically opposite poles of the perikaryon. The orientation of the polarity differed according to the rostrocaudal location of the neuron. The appearance of a polarized dendritic tree during the first (immature) phase was transient and closely coincident with IA negativity. Following the development of adult-like electrophysiological characteristics, i.e., IA positivity, nucleus of the tractus solitarius neurons showed remarkably different morphological features (9 of 10 cells). These included a wide-spread branching of the dendritic tree in all directions, giving it a bushy appearance (cell body to dendrite ratio of 1:40). Numerous dendritic spines, growth cones on both dendrites and axons, and axon collateralization were present during both phases and indicate that nTS neurons during the two phases of early development demonstrate dynamic features of growth and maturation. The development of adult-like electrophysiological characteristics, i.e., IA positivity, progressively increased in the postnatal period. During the later part of the first postnatal week, twice as many neurons showed IA positivity in days P3 to P6 as compared with days P0 to P2. These results reveal the dynamic nature of neurons in the nTS during early development and illustrate the close link between morphology and functional characteristics in this region. We suggest that the establishment of adult-like morphology can be modified by appropriate environmental clues provided to nTS neurons during the initial (immature) phase of early postnatal development.
我们利用新生大鼠（出生后0至6天）脑干切片中孤束核（nTS）内细胞内标记神经元的电生理学和光学显微镜技术，来研究其发育过程中的功能与形态相关性。在电生理记录后，对用生物胞素进行细胞内注射的神经元进行三维重建，结果显示形态不成熟（表现为树突树的极化）与超极化电流注入结束时缺乏斜坡状电压轨迹（IA阴性）之间存在密切对应关系（所检查的8个细胞中有8个显示出这种相关性）。这些形态极化的IA阴性神经元在核周体的两个直径相对的极上表现出优先的树突芽生。极性的方向根据神经元的头尾位置而有所不同。在第一个（不成熟）阶段出现的极化树突树是短暂的，并且与IA阴性密切相关。在类似成年的电生理特征即IA阳性发展之后，孤束核神经元表现出明显不同的形态特征（10个细胞中有9个）。这些特征包括树突树向各个方向广泛分支，使其呈现出浓密的外观（细胞体与树突的比例为1:40）。在两个阶段都存在大量的树突棘、树突和轴突上的生长锥以及轴突侧支，这表明早期发育的两个阶段中的nTS神经元都表现出生长和成熟的动态特征。类似成年的电生理特征即IA阳性在出生后的时期逐渐增加。在出生后第一周的后期，与出生后0至2天相比，出生后3至6天显示IA阳性的神经元数量增加了一倍。这些结果揭示了早期发育过程中nTS神经元的动态性质，并说明了该区域形态与功能特征之间的紧密联系。我们认为，在出生后早期发育的初始（不成熟）阶段，为nTS神经元提供适当的环境线索可以改变类似成年形态的建立。
