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

我们发现，雌激素受体（ER）α在新生大鼠的面神经核和初级听皮层中有短暂表达。然而，这一表达的生物学意义仍然没有得到解释。用TUNEL法在孕16天（FE 16）至生后11天（PN 11）的胎鼠至新生鼠面神经核中未检测到凋亡信号。因此，这表明表达ER α的细胞不是那些在生命早期死亡的细胞。另一方面，ER α阳性细胞的出生日期是通过给孕妇BrdU，然后通过免疫组织化学检测ER信号来估计的。BrdU和ER α信号的共定位仅在受孕后11天和12天给予BrdU的那些样品中检测到（FE 11 -12）。因此，面神经核中的运动神经元被怀疑在FE 11 -12周围达到最终的细胞分裂，并且其中只有一部分表达ER α。由于ER信号消失后PN 14，我们的假设，只有未成熟的运动神经元含有ER信号的支持。另一方面，我们用免疫组织化学双标法检测了新生大鼠初级听皮层ER信号是否与神经肽Y（NPY）、Gleaning、P物质、胆囊收缩素8（CCK 8）和血管活性肠肽（VIP）等神经肽共表达。到目前为止，我们未能检测到ER α信号与任何这些肽的任何明显的共定位。然而，由于我们通过电子显微镜在海马锥体神经元的核内位点检测到ER α信号，因此雌二醇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.