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Updated: Dec 20, 2025
Isolation of Cortical Microglia with Preserved Immunophenotype and Functionality From Murine Neonates
Published on: January 30, 2014
Homeostatic state of microglia in a rat model of chronic sleep restriction
Shannon Hall1, Samüel Deurveilher1, George S Robertson2,3
1Department of Medical Neuroscience, Dalhousie University, Halifax, NS, Canada.
Abstract:
Chronic sleep restriction (CSR) negatively impacts brain functions. Whether microglia, the brain's resident immune cells, play any role is unknown. We studied microglia responses to CSR using a rat model featuring slowly rotating wheels (3 h on/1 h off), which was previously shown to induce both homeostatic and adaptive responses in sleep and attention. Adult male rats were sleep restricted for 27 or 99 h. Control rats were housed in locked wheels. After 27 and/or 99 h of CSR, the number of cells immunoreactive for the microglia marker ionized calcium-binding adaptor molecule-1 (Iba1) and the density of Iba1 immunoreactivity were increased in 4/10 brain regions involved in sleep/wake regulation and cognition, including the prelimbic cortex, central amygdala, perifornical lateral hypothalamic area, and dorsal raphe nucleus. CSR neither induced mitosis in microglia (assessed with bromodeoxyuridine) nor impaired blood-brain barrier permeability (assessed with Evans Blue). Microglia appeared ramified in all treatment groups and, when examined quantitatively in the prelimbic cortex, their morphology was not affected by CSR. After 27 h, but not 99 h, of CSR, mRNA levels of the anti-inflammatory cytokine interleukin-10 were increased in the frontal cortex. Pro-inflammatory cytokine mRNA levels (tumor necrosis factor-α, interleukin-1β, and interleukin-6) were unchanged. Furthermore, cortical microglia were not immunoreactive for several pro- and anti-inflammatory markers tested, but were immunoreactive for the purinergic P2Y12 receptor. These results suggest that microglia respond to CSR while remaining in a physiological state and may contribute to the previously reported homeostatic and adaptive responses to CSR.
Insights
Chronic sleep restriction increases microglia markers in key brain regions but does not alter their morphology or inflammatory state. These brain immune cells may support adaptive responses to sleep loss.
Area of Science:
- Neuroscience
- Immunology
- Sleep Research
Background:
- Chronic sleep restriction (CSR) impairs cognitive functions.
- The role of microglia, the brain's immune cells, in CSR is not well understood.
Purpose of the Study:
- To investigate microglial responses to CSR in a rat model.
- To determine if CSR affects microglial activation state, morphology, or inflammatory markers.
Main Methods:
- Adult male rats underwent CSR for 27 or 99 hours using a slowly rotating wheel.
- Microglia were assessed via ionized calcium-binding adaptor molecule-1 (Iba1) immunoreactivity, cell proliferation (bromodeoxyuridine), blood-brain barrier permeability (Evans Blue), and cytokine mRNA levels.
- Microglial morphology and expression of inflammatory markers were analyzed.
Main Results:
- CSR increased Iba1+ cell number and density in 4/10 brain regions associated with sleep and cognition.
- CSR did not induce microglial mitosis or compromise blood-brain barrier integrity.
- Microglial morphology remained ramified, and pro-inflammatory cytokine mRNA levels were unchanged, although interleukin-10 mRNA increased after 27h CSR.
Conclusions:
- Microglia respond to CSR by increasing their presence in specific brain areas.
- Microglial responses to CSR occur without significant activation or morphological changes, suggesting a physiological role.
- These findings indicate microglia may contribute to homeostatic and adaptive processes during sleep restriction.
