Farel P B, Boyer A
Department of Physiology, School of Medicine, University of North Carolina, Chapel Hill 27599-7545, USA.
J Comp Neurol. 1999 Jul 26;410(2):171-7.
The effect of lumbar spinal nerve (SN) transection on estimates of neuron number was investigated in the dorsal root ganglia (DRGs) of juvenile bullfrogs (Rana catesbeiana). SN8 and SN10 were transected on one side, and SN9 was left intact. Two weeks after nerve injury, estimates of neuron number in DRG8 and DRG10 on both the operated and unoperated sides were more than twice the estimates obtained from control animals. Neuron number in the uninjured DRG9 was also elevated relative to that of control animals. Eight weeks after axotomy, differences in neuron number were less apparent. The mean cross-sectional area of DRG neurons was reduced 2 weeks after nerve injury in all DRGs. The decrease in mean area was the result of the addition of neurons to the smallest size classes. These data are discussed in the context of previous results showing that neurons are added as juvenile frogs grow to adult size (St. Wecker and Farel [1994] J. Comp. Neurol. 342:430-438). This addition results from the maturation of a population of incompletely differentiated neurons (Meeker and Farel [1997] J. Comp. Neurol. 389:569-576). The present results suggest that axotomy precipitates differentiation of these incompletely differentiated neurons, perhaps as a compensatory response to nerve injury.
在幼年牛蛙（牛蛙）的背根神经节（DRG）中，研究了腰脊髓神经（SN）横断对神经元数量估计的影响。一侧横断SN8和SN10，保留SN9完整。神经损伤两周后，手术侧和未手术侧DRG8和DRG10中的神经元数量估计值是对照动物的两倍多。未损伤的DRG9中的神经元数量相对于对照动物也有所增加。轴突切断八周后，神经元数量的差异不太明显。神经损伤两周后，所有DRG中DRG神经元的平均横截面积均减小。平均面积的减小是由于最小尺寸类别的神经元增加所致。这些数据是在先前结果的背景下进行讨论的，先前结果表明，随着幼蛙成长为成体大小，神经元会增加（St. Wecker和Farel [1994] J. Comp. Neurol. 342:430 - 438）。这种增加是由于一群未完全分化的神经元成熟所致（Meeker和Farel [1997] J. Comp. Neurol. 389:569 - 576）。目前的结果表明，轴突切断促使这些未完全分化的神经元分化，这可能是对神经损伤的一种代偿反应。
