Related Experiment Video
Updated: Oct 13, 2025
Flow Cytometry and Single-Cell Analysis for Characterizing Microglia Activation in Early Postnatal Mouse Brain Development
Published on: October 3, 2025
The Effect of Valproic Acid Exposure throughout Development on Microglia Number in the Prefrontal Cortex, Hippocampus
Janace J Gifford1, Pooja Deshpande1, Priyanka Mehta1
1Psychology, Rutgers University, 152 Frelinghuysen Road, New Brunswick, NJ 08854, United States.
Abstract:
Microglia serve as resident immune cells in the brain, responding to insults and pathological developments. They have also been implicated in shaping synaptic development and regulation. The present study examined microglial cell density in a number of brain regions across select postnatal (P) ages along with the effects of valproic acid (VPA) on microglia density. Specifically, C57BL/6JCx3CR1+/GFP mice were examined for microglial cell number changes on P7, P14, P30, and P60 under baseline conditions and following 400 mg/kg VPA or saline. The prefrontal cortex (PFC), hippocampus and cerebellum were observed. Under control conditions, the results showed a shift in the number of microglia in these brain areas throughout development with a peak density in the hippocampus at P14 and an increase in PFC microglial numbers from P15 to P30. Interestingly, VPA treatment enhanced microglial numbers in a region-specific manner. VPA at P7 increased microglial cell number in the hippocampus and cerebellum whereas P14 VPA treatment altered microglial density in the cerebellum only. Cerebellar increases also occurred after VPA at P30, and were attended by an effect of increased numbers in the PFC. Finally, animals treated with VPA at P60 exhibited decreased microglia density in the hippocampus only. These results suggest rapid VPA-induced increases in microglial cell density in a developmentally-regulated fashion which differs across distinct brain areas. Furthermore, in the context of prior reports that early VPA causes excitotoxic damage, the present findings suggest early VPA exposure may provide a model for studying altered microglial responses to early toxicant challenge.
Insights
Valproic acid (VPA) alters brain microglia density in a developmental and region-specific manner. Early VPA exposure may model altered microglial responses to toxicant challenges in the developing brain.
Area of Science:
- Neuroscience
- Immunology
- Developmental Biology
Background:
- Microglia are brain immune cells involved in neural development and response to injury.
- Valproic acid (VPA) is known to cause excitotoxic damage in early development.
Purpose of the Study:
- To investigate the effects of VPA on microglial cell density across different brain regions and postnatal ages.
- To understand the developmental trajectory of microglial responses to VPA exposure.
Main Methods:
- Examined microglial cell density in C57BL/6JCx3CR1+/GFP mice at postnatal days P7, P14, P30, and P60.
- Administered VPA (400 mg/kg) or saline, assessing cell numbers in the prefrontal cortex (PFC), hippocampus, and cerebellum.
- Analyzed microglial cell density changes under baseline and VPA-treated conditions.
Main Results:
- Microglial density naturally shifts during development, peaking in the hippocampus at P14 and increasing in the PFC from P15-P30.
- VPA treatment increased microglial numbers in a region- and age-dependent manner.
- Specific findings include VPA-induced increases in the hippocampus and cerebellum at P7, cerebellum at P14, cerebellum and PFC at P30, and decreased density in the hippocampus at P60.
Conclusions:
- VPA rapidly influences microglial cell density in a developmentally regulated and brain region-specific pattern.
- Early VPA exposure may serve as a model for studying microglial responses to early toxicant challenges.
- Findings highlight the dynamic role of microglia in brain development and response to environmental factors.
