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Transient expression of estrogen receptor-immunoreactivity (ER-IR) in the layer V of the developing rat cerebral
M Yokosuka1, H Okamura, S Hayashi
1Department of Anatomy and Embryology, Tokyo Metropolitan Institute for Neuroscience, Japan.
Insights
Estrogen receptor-immunoreactivity (ER-IR) transiently appears in specific rat brain regions during development, particularly the auditory cortex. These transient signals may be crucial for neuronal maturation in the auditory circuit.
Area of Science:
- Neuroscience
- Developmental Biology
- Endocrinology
Background:
- Estrogen receptors play critical roles in brain development and function.
- Understanding the temporal and spatial expression of estrogen receptors is key to deciphering their influence on neural circuits.
Purpose of the Study:
- To investigate the occurrence and developmental pattern of estrogen receptor-immunoreactivity (ER-IR) in the rat cerebral cortex.
- To determine the specific cortical layers and time windows of ER-IR expression during neonatal and adult stages.
Main Methods:
- Immunohistochemistry was used to detect ER-IR in the cerebral cortex of rats at various postnatal days (PD1, PD5, PD7, PD10, PD13, PD15, PD21) and in adults.
- Adjacent sections were stained with Cresyl violet and acetylcholinesterase (AChE) histochemistry to precisely identify the location of ER-IR positive cells.
Main Results:
- ER-IR was absent in the neocortex of newborn rats (PD1, PD5).
- Distinct ER-IR emerged in layer V of the auditory cortex around PD7, peaking at PD10, and was also weakly detected in somatosensory and visual cortices at PD10.
- These transient signals in layer V disappeared by PD15, while weak ER-IR reappeared sporadically in layer II of the neocortex in PD21 and adult rats.
Conclusions:
- Estrogen receptor expression in the rat neocortex is transient and developmentally regulated.
- The transient ER-IR in the auditory cortex during a critical developmental window may play a role in the maturation and establishment of auditory neurons.
- The findings highlight the dynamic influence of estrogen on developing neural circuits.
Abstract:
Occurrence of estrogen receptor-immunoreactivity (ER-IR) in the cerebral cortex was examined in neonatal and adult rats. In newborn rats of postnatal day 1 (= day of birth) and postnatal day 5 (PD1 and PD5, respectively), ER-IR was not evident in the neocortex. On postnatal days 7, 10 and 13 (PD7, PD10 and PD13 respectively), a group of cells with distinct ER-IR appeared in the layer V of the auditory cortex. At the PD10, weak but specific ER-IR were also appeared in the somatosensory and the visual cortices. Among these areas, the ER-IR positive neurons occurred most frequently in the auditory cortex at PD10 rats. By examination of adjacent sections, one stained with Cresyl violet and the another stained with acethylcholinesterase (AChE) histochemistry, it was revealed that the region with ER-IR at PD7 to PD13 was limited to layer V of the neocortex. These signals, however, disappeared at PD15. In layer II of the neocortex, on the other hand, weak ER-IR signals were detected throughout the area sporadically at PD21 and in adults. The ER-IR detected transiently in the auditory cortex by the antiserum might contribute to maturation and establishment of the neurons of the rat auditory circuit.