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Published on: June 29, 2015
Peripheral nerve injury induces a transitory microglial reaction in the rat infralimbic cortex
Paul Chu Sin Chung1, Tania Panigada1, Romain Cardis1
1Pain Center, Department of Anesthesiology, University Hospital Center (CHUV) and Faculty of Biology and Medicine (FBM), University of Lausanne, 1011 Lausanne, Switzerland; Department of Fundamental Neurosciences, Faculty of Biology and Medicine (FBM), University of Lausanne, 1005 Lausanne, Switzerland.
Abstract:
Undeniable evidence shows that microglia in the spinal cord undergo marked reactions following peripheral injuries. However, only rare studies have investigated the possible short and long term microglial reaction in brain regions following peripheral nerve injury and its interspecies specificities. In the present study we examined microglia in subdivisions of the prefrontal cortex in mice and rats, 7days and 42days after spared nerve injury (SNI) of the sciatic nerve. We show that a bilateral increase of microglial density takes place in the infralimbic cortex in rats 7days post-injury (sham vs. SNI, n=5: ipsilateral 35.4% increase of the median, p=0.0317; contralateral 24.9% increase of the median, p=0.0079), without any detectable change in the other investigated regions, namely the anterior cingulate, prelimbic and agranular insular cortices. In mice, no observable difference could be found in any region at both time points, neither using Iba-1 immunostaining nor with CX3CR1-eGFP animals. Our results indicate that a transitory, species-specific and highly regionalized microglial reaction takes place in the prefrontal cortex following peripheral nerve injury.
Insights
Peripheral nerve injury triggers a temporary, species-specific microglial reaction in specific rat brain regions. This microglial response was not observed in mice, highlighting interspecies differences in neuroinflammation following injury.
Area of Science:
- Neuroscience
- Immunology
- Neuroinflammation
Background:
- Microglia in the spinal cord react to peripheral injuries.
- Limited research exists on microglial responses in brain regions after peripheral nerve injury and their species-specific differences.
Purpose of the Study:
- To investigate short- and long-term microglial reactions in prefrontal cortex subdivisions after peripheral nerve injury.
- To compare these reactions between rats and mice.
Main Methods:
- Spared nerve injury (SNI) model of the sciatic nerve was used in adult male rats and mice.
- Microglia were examined in prefrontal cortex subdivisions (infralimbic, anterior cingulate, prelimbic, agranular insular cortices) 7 and 42 days post-injury.
- Iba-1 immunostaining and CX3CR1-eGFP reporter mice were utilized.
Main Results:
- Rats showed a bilateral increase in microglial density in the infralimbic cortex 7 days post-SNI (ipsilateral: 35.4% increase; contralateral: 24.9% increase).
- No significant microglial changes were detected in other examined prefrontal cortex regions in rats.
- No observable microglial differences were found in any region in mice at both time points.
Conclusions:
- Peripheral nerve injury induces a transient, species-specific, and highly regionalized microglial reaction in the rat prefrontal cortex.
- These findings suggest significant interspecies variability in neuroinflammatory responses within the brain following peripheral nerve damage.
