Analysis of transient expression of estrogen receptor in the newborn rat brain

我们发现，雌激素受体(ER)α在新生大鼠面神经核和初级听觉皮质中瞬时表达。然而，这个表达的生物学意义仍然没有得到解释。在妊娠16天(FE16)至出生11天(PN11)的胎鼠至新生大鼠面神经核内未检测到任何细胞凋亡信号。因此，这表明表达ERα的细胞不是那些在生命早期死亡的细胞。另一方面，通过给孕妇注射BrdU，然后对ER信号进行免疫组织化学检测，来估计ERα阳性细胞的出生日期。仅在怀孕后11天和12天给予BrdU的样本中才检测到BrdU和ERα信号的共同定位(FE11-12)。因此，面核中的运动神经元被认为在FE11-12左右达到最终的细胞分裂，其中只有一部分表达ERα。由于内质网信号在PN14之后消失，支持我们的假设，即只有未成熟的运动神经元含有内质网信号。另一方面，采用双重免疫组织化学方法检测新生大鼠初级听皮质内ER信号是否与神经肽Y(NPY)、GLEING、P物质、CCK8、VIP等神经肽共表达。到目前为止，我们还没有检测到ERα信号与这些肽中的任何一个有明显的共定位。然而，由于我们通过电子显微镜在海马锥体神经元的核外部位检测到ERα信号，因此雌二醇有可能通过雌激素受体发挥核外作用。

We have found that estrogen receptor (ER) alpha is expressed transiently in the facial nucleus and in the primary auditory cortex of new born rats. However, biological meaning of this expression is still left unexplained. Using TUNEL method, we failed to detect any apoptotic signals in the facial nucleus of fetal to newborn rats between 16 days after conception (FE16) and 11days after birth (PN11). Thus, it is suggested that the cells expressing ER alpha are not those die early in the life. On the other hand, the birth date of the ER alpha positive cells was estimated by giving BrdU to pregnant mothers followed by immunohistochemical detection of ER signals. Colocalization of the BrdU and ER alpha signals was only detected in those samples given BrdU at 11 and 12 days after conception (FE11-12). Thus, motoneurons in the facial nucleus is suspected to attain final cell division around FE11-12 and only a part of them express ER alpha. Since ER signals disappear after PN14, our hypothesis that only immature motoneurons contain ER signals is supported. On the other hand, we examined in the primary auditory cortex of the newborn rats if ER signals were co-expressed with any neuropeptides, such as neuropeptides Y (NPY), gleaning, substance P, cholecystokinine 8 (CCK8), and vasoactive intestinal peptide (VIP) by using double immunohistochemistry method. So far we failed to detect any distinct Colocalization of ER alpha signals with any of these peptides. However, since we detected ER alpha signals in extranuclear loci by electron microscopy in the hippocampal pyramidal neurons, there is a possibility of extra-nuclear action of estradiol through estrogen receptor.