Miller M W, al-Rabiai S
Research Service, Veterans Affairs Medical Center, University of Iowa College of Medicine, Iowa City.
Alcohol Clin Exp Res. 1994 Apr;18(2):346-54. doi: 10.1111/j.1530-0277.1994.tb00024.x.
We examined the effect of gestational ethanol exposure on the number of axons in the caudal pyramidal tract. Between gestational day (G) 6 and G21, inclusive, pregnant rats were fed a liquid ethanol-containing diet (Et), an isocaloric liquid control diet (Ct), or a diet of chow and water (Ch). On postnatal day 30, the offspring of these rats were killed and their caudal medullas were processed for electron microscopy. The overall size of the pyramidal tract and the space occupied by the axons was smaller in the Et-treated rats than in the Ct-treated rats. The myelinated axons were smaller and the myelin was thinner in the Et-treated rats than in the Ct-treated rats. These decreases produced an ethanol-induced increase in the density of axons in the pyramidal tract. In particular, the density of myelinated axons (but not nonmyelinated axons) was greater in Et-treated rats. The net result was that the estimated number of axons in the pyramidal tracts of the Et-treated rats was not significantly different than the number in the Ch- and Ct-treated rats. The present data demonstrate that ethanol does not affect the absolute number of axons in the pyramidal tract. As a result of the ethanol-induced microencephaly, however, the data translate into a relative increase in the number of pyramidal tract axons. This relative increase matches the ethanol-induced increase in the density of corticospinal projection neurons that may result from the retention of a developmentally exuberant projection.
我们研究了孕期乙醇暴露对尾侧锥体束中轴突数量的影响。在孕期第6天至第21天（含）期间，给怀孕大鼠喂食含乙醇的液体饲料（Et组）、等热量的液体对照饲料（Ct组）或普通饲料与水（Ch组）。在出生后第30天，处死这些大鼠的后代，并对其尾侧延髓进行电子显微镜处理。与Ct组大鼠相比，Et组大鼠锥体束的整体大小以及轴突所占空间较小。与Ct组大鼠相比，Et组大鼠的有髓轴突较小，髓鞘较薄。这些减少导致乙醇诱导锥体束中轴突密度增加。特别是，Et组大鼠中有髓轴突（而非无髓轴突）的密度更大。最终结果是，Et组大鼠锥体束中轴突的估计数量与Ch组和Ct组大鼠的数量无显著差异。目前的数据表明，乙醇不影响锥体束中轴突的绝对数量。然而，由于乙醇诱导的小头畸形，这些数据转化为锥体束轴突数量的相对增加。这种相对增加与乙醇诱导的皮质脊髓投射神经元密度增加相匹配，这可能是由于保留了发育旺盛的投射所致。
