Ruiz-Marcos A, Cartagena Abella P, García García A, Escobar del Rey F, Morreale de Escobar G
Unidad de Neuroanatomia, Instituto Cajal (C.S.I.C.), Madrid, Spain.
Exp Brain Res. 1988;73(3):583-8. doi: 10.1007/BF00406617.
We have previously shown (Ruiz-Marcos et al. 1980, 1982) that thyroidectomy (T) performed in rats at 40 days of age, well past the neonatal period of development, results by 80-90 days of age in a decrease of the number of spines along the shaft of pyramidal neurons with the cell body in layer V in the visual area of the cerebral cortex. We have here studied how soon after the operation an effect on spine number and distribution may be observed. We have found that the response of these neurons to T is very rapid: a decrease in the number of spines/shaft between T and age-paired controls (C) rats is statistically significant by the earliest period of observation, namely 5 days after T. These results may be related to those of Dembri et al. (1983) showing that T performed in adult rats decreases the activity of Type I RNA polymerase by 5 days after the operation. It is possible that T impairs the synthesis of some compound(s) necessary for the formation and maintenance of spines. The present results suggest that spine number is not a fixed structure of the apical shaft once brain development is over, but is in a state of continuous formation and degradation. We have further observed that the effect of T performed at 40 days of age is more pronounced in the distal part of the shaft than on the rest, a result similar to that found after neonatal T (Ruiz-Marcos et al. 1982). However, contrary to findings after early hypothyroidism, T at 40 days of age does not distort the distribution of spines along the shaft.
我们之前已经表明（鲁伊斯 - 马科斯等人，1980年，1982年），在40日龄的大鼠身上进行甲状腺切除术（T），此时已远超过新生儿发育阶段，到80 - 90日龄时，位于大脑皮质视觉区第V层、胞体在锥体细胞轴突上的棘突数量会减少。我们在此研究了手术后多久能观察到对棘突数量和分布的影响。我们发现这些神经元对甲状腺切除术的反应非常迅速：在最早的观察期，即甲状腺切除术后5天，甲状腺切除组（T）与年龄配对的对照组（C）大鼠相比，轴突上棘突数量的减少具有统计学意义。这些结果可能与登布里等人（1983年）的结果相关，他们表明成年大鼠进行甲状腺切除术后5天，I型RNA聚合酶的活性降低。有可能甲状腺切除术损害了棘突形成和维持所需的某些化合物的合成。目前的结果表明，一旦大脑发育结束，棘突数量并非顶轴的固定结构，而是处于持续形成和降解的状态。我们进一步观察到，40日龄时进行甲状腺切除术的影响在轴突的远端比其他部位更明显，这一结果与新生儿期进行甲状腺切除术后的发现相似（鲁伊斯 - 马科斯等人，1982年）。然而，与早期甲状腺功能减退后的发现相反，40日龄时进行甲状腺切除术不会扭曲棘突沿轴突的分布。
