Popken G J, Farel P B
Department of Physiology and Curriculum in Neurobiology, University of North Carolina School of Medicine, Chapel Hill 27599, USA.
J Comp Neurol. 1997 Sep 15;386(1):8-15.
Postnatal neuron addition, if it occurred, would have profound implications both for the conceptualization of developmental processes and for efforts directed at replacing neurons that were lost to injury or disease. Although dorsal root ganglia (DRGs) offer the advantages of clear boundaries and functional homogeneity, studies comparing neuron number in the DRGs of animals of different ages or sizes have yielded conflicting results. In the present study, neuron number in DRGs L3-L6 was compared in neonatal (approximately 11 days old, mean weight of 24.5 g, mean volume of 25 cm3) and adult (approximately 80 days old, mean weight of 373.5 g, mean volume of 346 cm3) male Sprague-Dawley rats. Estimates of neuron number were derived by using both stereological (physical disector) and profile-counting (one or more nucleoli within a nucleus) methods. The reliability and validity of the two methods were evaluated by comparing estimates of neuron number with those derived from three-dimensional reconstruction of a subset of neurons. The recommended protocol for using the physical disector was found to give accurate estimates of neuron number, but the heterogeneous distribution of neurons in the ganglion led to sampling errors of up to 50%. Reliability was improved by increasing the number of disector pairs examined. Counts of nuclear/nucleolar profiles were more reliable, but introduced a bias that worked against the experimental hypothesis in that estimates of neuron number in neonates exceeded actual values. Nonetheless, both methods indicated that adult rats had more DRG neurons than did neonates. Profile counts were 19% higher in adults (P < .01, two-tailed t-test); and data obtained by using the physical disector showed that adult rats had 28% more neurons than did neonates (P < .05). The difference in neuron number between adults and neonates could be due either to neuron proliferation or to late differentiation of neurons that do not assume a typical appearance until adulthood.
出生后神经元的增加（如果确实发生的话），将对发育过程的概念化以及针对替换因损伤或疾病而丢失的神经元的努力产生深远影响。尽管背根神经节（DRG）具有边界清晰和功能同质性的优点，但比较不同年龄或大小动物的DRG中神经元数量的研究结果却相互矛盾。在本研究中，比较了新生（约11日龄，平均体重24.5克，平均体积25立方厘米）和成年（约80日龄，平均体重373.5克，平均体积346立方厘米）雄性Sprague-Dawley大鼠L3-L6 DRG中的神经元数量。通过使用体视学（物理分割器）和轮廓计数（细胞核内一个或多个核仁）方法来估算神经元数量。通过将神经元数量的估算值与从一部分神经元的三维重建中得出的估算值进行比较，评估了这两种方法的可靠性和有效性。发现使用物理分割器的推荐方案能够准确估算神经元数量，但神经节中神经元的不均匀分布导致抽样误差高达50%。通过增加检查的分割器对数量提高了可靠性。核/核仁轮廓计数更可靠，但引入了一种与实验假设相悖的偏差，即新生儿神经元数量的估算值超过了实际值。尽管如此，两种方法均表明成年大鼠的DRG神经元比新生大鼠更多。成年大鼠的轮廓计数高19%（P <.01，双侧t检验）；使用物理分割器获得的数据显示成年大鼠的神经元比新生大鼠多28%（P <.05）。成年大鼠和新生大鼠之间神经元数量的差异可能是由于神经元增殖或神经元的晚期分化，这些神经元直到成年才呈现典型外观。
