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Sex differences and laterality of insulin receptor distribution in developing rat hippocampus: an immunohistochemical
Javad Hami1, Hamed Kheradmand, Hossein Haghir
1Department of Anatomical Sciences, School of Medicine, Birjand University of Medical Sciences, Birjand, Iran.
Insights
Insulin receptor (InsR) distribution in newborn rat hippocampus shows significant differences between sexes and sides by P14. These findings reveal developmental patterns contributing to hippocampal sexual dimorphism and asymmetry.
Area of Science:
- Neuroscience
- Developmental Biology
- Endocrinology
Background:
- The hippocampus plays a crucial role in learning and memory.
- Insulin receptors (InsR) are vital for neuronal function and plasticity.
- Understanding InsR distribution is key to deciphering hippocampal development and function.
Purpose of the Study:
- To investigate the regional and temporal distribution of insulin receptors (InsR) in the newborn rat hippocampus.
- To compare InsR distribution between male and female rats.
- To examine potential left-right asymmetries in InsR distribution during early development.
Main Methods:
- Immunohistochemistry was used to identify insulin receptor (InsR)-immunoreactive-positive (InsR+) cells.
- Analysis was performed on postnatal days 0, 7, and 14.
- Comparisons were made between hippocampal subregions (CA1, CA3, DG), sexes, and sides (left/right).
Main Results:
- InsR+ cell counts in CA1 increased until P7, while CA3 showed a marked increase from P0 to P14.
- A significant decline in InsR+ cells was observed in the dentate gyrus (DG) during the same period.
- Sex and side differences in InsR distribution emerged by P7 and P14, particularly in CA1, CA3, and DG.
Conclusions:
- Insulin receptor distribution in the developing rat hippocampus is not uniform.
- Significant sexual dimorphism and left-right asymmetry in InsR patterns are established during early postnatal development.
- These differential InsR distributions may contribute to observed sex differences and lateralization in hippocampal function.
Abstract:
This study aimed to compare the regional distribution of insulin receptor in various portions of newborn rat hippocampus on postnatal days 0 (P0), 7 (P7), and 14 (P14) between male/female and right/left hippocampi. We found that the number of insulin receptor (InsR)-immunoreactive-positive (InsR+) cells in CA1 continued to increase until P7 and remained unchanged thereafter. A marked increase in distribution of InsR+ cells in CA3 from P0 to P14 was observed, although there was a significant decline in the number of InsR+ cells in dentate gyrus (DG) at the same time. No differences between the right/left and male/female hippocampi were detected at P0 (P > 0.05). Seven-day-old female rats showed a higher number of labeled cells in the left than in the right hippocampus. Moreover, the differences between the number of InsR+ cells in area CA1 and CA3 were statistically significant between males and females (P < 0.05). At P14, the number of InsR+ cells was significantly higher in CA1 and DG of males, especially in the right one (P < 0.05). These results indicate the existence of a differential distribution pattern of InsR between the left/right and male/female hippocampi. Together with other mechanisms, these differences may underlie sexual dimorphism and left/right asymmetry in the hippocampus.
