Parson S H, Ribchester R R
Department of Anatomy, University Medical School, Edinburgh, Scotland.
J Neurobiol. 1995 Jan;26(1):1-16. doi: 10.1002/neu.480260102.
Targets in limb regions of the chick embryo are further removed from the dorsal root ganglia that innervate them compared with thoracic ganglion-to-target distances. It has been inferred that axons grow into the limb regions two to three times faster than into nonlimb regions. We tested whether the differences were due to intrinsic properties of the neurons located at different segmental levels. Dorsal root ganglia (DRG) were isolated from the forelimb, trunk, and hind limb regions of stage 25-30 embryos. Neurite outgrowth was measured in dissociated cell culture and in cultures of DRG explants. Although there was considerable variability in the amount of neurite outgrowth, there were no substantive differences in the amount or the rate of outgrowth comparing brachial, thoracic, or lumbosacral neurons. The amount of neurite outgrowth in dissociated cell cultures increased with the stage of development. Overall, our data suggest that DRG neurons express a basal amount of outgrowth, which is initially independent of target-derived neurotrophic influences; the magnitude of this intrinsic growth potential increases with stage of development; and the neurons of the DRG are not intrinsically specified to grow neurites at rates that are matched to the distance they are required to grow to make contact with their peripheral targets in vivo. We present a speculative model based on Poisson statistics, which attempts to account for the variability in the amount of neurite outgrowth from dissociated neurons.
与胸神经节到靶标的距离相比，鸡胚肢体区域的靶标与支配它们的背根神经节的距离更远。据推测，轴突向肢体区域生长的速度比向非肢体区域生长的速度快两到三倍。我们测试了这些差异是否是由于位于不同节段水平的神经元的内在特性所致。从第25 - 30阶段胚胎的前肢、躯干和后肢区域分离出背根神经节（DRG）。在解离细胞培养物和DRG外植体培养物中测量神经突生长。尽管神经突生长量存在相当大的变异性，但比较臂部、胸部或腰骶部神经元的生长量或生长速率时，没有实质性差异。解离细胞培养物中的神经突生长量随着发育阶段的增加而增加。总体而言，我们的数据表明，DRG神经元表达一定量的生长，这种生长最初独立于靶标衍生的神经营养影响；这种内在生长潜力的大小随着发育阶段的增加而增加；并且DRG的神经元在本质上并没有被指定以与它们在体内生长以接触其外周靶标所需的距离相匹配的速率生长神经突。我们提出了一个基于泊松统计的推测模型，该模型试图解释解离神经元神经突生长量的变异性。
