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Abstract:
The rat brain has been studied between 6 hours after birth and 100 days, using histochemical techniques for acid phosphatase and peroxidase, and silver impregnation for microglial cells. The results indicate that microglia come initially from acid phosphatase-positive cells of the meninges. These invade the nervous parenchyma and transform into ramified microglia. At 3 days of age similar cells are present on the outer surface of the large blood vessels, from which site they migrate into the nervous parenchyma. In 100 days old rats the acid phosphatase-positive cells are practically all pericytes. None of the microglial cells or their precursors give a positive reaction for peroxidase.
Insights
Microglia in rat brains originate from meningeal cells, migrating into brain tissue. These cells later appear to develop from pericytes, with no peroxidase activity observed in microglia or their precursors.
Area of Science:
- Neuroscience
- Developmental Biology
- Histology
Background:
- Microglia are the resident immune cells of the central nervous system.
- Their origin and developmental trajectory in the early postnatal brain remain areas of active investigation.
- Understanding microglial origins is crucial for comprehending neurodevelopment and neuroinflammation.
Purpose of the Study:
- To investigate the origin and early development of microglia in the postnatal rat brain.
- To identify the precursor cells and migratory pathways of microglia.
- To characterize the enzymatic profiles of microglial precursors and mature microglia.
Main Methods:
- Histochemical techniques were employed to detect acid phosphatase and peroxidase activity.
- Silver impregnation was used for the visualization of microglial cells.
- The study spanned a developmental period from 6 hours to 100 days after birth in rats.
Main Results:
- Microglia originate from acid phosphatase-positive cells in the meninges, which invade the nervous parenchyma.
- By postnatal day 3, similar cells are observed migrating from the surface of large blood vessels into the parenchyma.
- In adult rats (100 days), acid phosphatase-positive cells are predominantly pericytes.
- No peroxidase activity was detected in microglia or their identified precursors.
Conclusions:
- The study suggests a meningeal origin for microglia, with a potential transition or relationship with pericytes during development.
- Microglial cells do not exhibit peroxidase activity, distinguishing them from certain other cell types.
- These findings contribute to the understanding of microglial ontogeny and cellular lineage in the developing brain.