Davis M R, Constantine-Paton M
J Comp Neurol. 1983 Dec 20;221(4):453-65. doi: 10.1002/cne.902210408.
Central and peripheral connectivity patterns of hyperplastic dorsal root ganglia (DRGs) in Rana pipiens are examined in order to determine the relative roles of peripheral and central contacts in the production of DRG hyperplasias. The hyperplasias are produced in the intact hindlimb DRGs after the removal in tadpoles and young postmetamorphic frogs of neighboring DRGs (Davis and Constantine-Paton, '83). The peripheral target zones of the hyperplastic DRGs, determined by physiological recordings of sensory receptive fields, are found to undergo a significant degree of expansion relative to controls. Peripheral expansion is most pronounced in caudalmost DRG 10, and this effect occurs in experimental animals operated during larval and postmetamorphic stages. Further, anatomical labelling of peripheral sensory fibers coursing to the hindlimb reveals that the hyperplastic DRG 10 actually contains additional fibers projecting to the denervated regions. The central projection of the hyperplastic DRG 10 does not show corresponding increases in longitudinal arborization after the application of horseradish peroxidase to the appropriate dorsal roots. These observations are made on some of the same experimental animals in which peripheral fields are shown to have vastly expanded. We conclude that the peripheral processes of the hyperplastic DRGs are less rigidly specified than the central terminations, and that it is the periphery which plays the primary role in controlling the cell numbers increases. A second aim of this investigation is to identify whether sexually dimorphic connectivity patterns in normal frogs explain the production of DRG 10 hyperplasias exclusively in male experimental animals (Davis and Constantine-Paton, '83). We apply the same techniques used in our connectivity studies of hyperplastic DRGs to the investigation of connectivity patterns of DRG 10s in normal males and females. No sex-dependent differences in peripheral and central connectivity are found. Thus, since normal male and female frogs possess an equivalent amount of target space for DRG 10, the unique production of hyperplasias in male experimental animals cannot be explained solely on the basis of connectivity. We speculate on what other factors may be involved.
为了确定外周和中枢接触在蛙背根神经节（DRG）增生形成过程中的相对作用，研究了豹蛙增生性背根神经节的中枢和外周连接模式。在蝌蚪和变态后的幼蛙中去除相邻的背根神经节后，完整后肢的背根神经节会出现增生（Davis和Constantine-Paton，1983年）。通过感觉感受野的生理记录确定，增生性背根神经节的外周靶区相对于对照组有显著程度的扩张。外周扩张在最尾端的DRG 10中最为明显，且这种效应在幼虫期和变态后阶段进行手术的实验动物中均会出现。此外，对后肢外周感觉纤维的解剖标记显示，增生性DRG 10实际上包含投射到去神经支配区域的额外纤维。在用辣根过氧化物酶处理相应的背根后，增生性DRG 10的中枢投射在纵向分支上并未显示出相应增加。这些观察结果是在一些外周感觉野已被证明大幅扩张的相同实验动物上得出的。我们得出结论，增生性背根神经节的外周突起比中枢终末的特异性更低，并且在外周控制细胞数量增加方面起主要作用。本研究的第二个目的是确定正常青蛙中的性别二态性连接模式是否能解释为什么只有雄性实验动物会出现DRG 10增生（Davis和Constantine-Paton，1983年）。我们将用于增生性背根神经节连接研究的相同技术应用于正常雄性和雌性青蛙DRG 10连接模式的研究。未发现外周和中枢连接存在性别依赖性差异。因此，由于正常雄性和雌性青蛙的DRG 10具有等量的靶空间，雄性实验动物中增生的独特产生不能仅基于连接性来解释。我们推测可能涉及其他哪些因素。
