Abreu-Villaça Y, Schanuel S M, Schmidt S L
Laboratório de Neurofisiologia e Avaliação Neurocomportamental, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil.
Int J Dev Neurosci. 2001 Nov;19(7):639-47. doi: 10.1016/s0736-5748(01)00052-1.
A previous study reported that adult mice irradiated at the 16th embryonic day present a severe neuronal number reduction in the dorsal lateral geniculate thalamic nucleus. In the present study, we investigated the time course of the effects of prenatal irradiation on this thalamic nucleus. One day after irradiation, a great number of pyknotic figures were seen mainly in the cerebral proliferative zones. In the geniculate nucleus, only scattered pyknotic figures were identified. On the first week after birth, the geniculate nucleus presented frequent pyknotic figures. From five days after birth onwards, a severe shrinkage of the occipital cortex and a great reduction in the geniculate nucleus neuronal number were found. On the second week after birth this neuronal number reduction reached as high as 75%. At each postnatal analyzed age, severe volumetric geniculate nucleus shrinkage was combined to non-significant neuronal density variations. The presence of few pyknotic figures in the geniculate nucleus one day after irradiation and its delayed neuronal loss indicate an indirect effect of irradiation. We suggest that the effect upon the geniculate nucleus is secondary to the damage of the occipital cortex. A possible interpretation for thalamic neuronal loss is that geniculate neurons fail to establish cortical arbors after major target loss. In this case, the loss of trophic support should also be considered.
先前的一项研究报告称，在胚胎第16天接受辐射的成年小鼠，其背侧外侧膝状体丘脑核中的神经元数量严重减少。在本研究中，我们调查了产前辐射对该丘脑核影响的时间进程。辐射后一天，大量固缩核主要出现在大脑增殖区。在膝状体核中，仅发现散在的固缩核。出生后第一周，膝状体核出现频繁的固缩核。从出生后五天起，发现枕叶皮质严重萎缩，膝状体核神经元数量大幅减少。出生后第二周，这种神经元数量减少高达75%。在每个分析的出生后年龄，膝状体核严重的体积缩小与神经元密度无显著变化同时存在。辐射后一天膝状体核中少量固缩核的存在及其延迟的神经元丢失表明辐射的间接作用。我们认为对膝状体核的影响是枕叶皮质损伤的继发结果。丘脑神经元丢失的一种可能解释是，在主要靶标丧失后，膝状体神经元未能建立皮质分支。在这种情况下，也应考虑营养支持的丧失。
