Publication details

Bilateral activation of microglia and expression of TLR4 in the trigeminal sbnucleus caudalis after unilateral infraorbital nerve injury

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Year of publication 2012
Type Conference abstract
MU Faculty or unit

Central European Institute of Technology

Description The activated microglia contribute to increased excitation of neurons, neuropathic pain induction and maintenance. Microglia become activated after peripheral nerve injury in the spinal and trigeminal models of both neuropathic pain and produce various cytokines and inflammatory mediators. TLR4 is one of the pathogen recognition receptor which is expressed by glial cells in mediating neuroinflammatory response. The goal of our work was to investigate bilateral activation of microglia and expression of TLR4 in the trigeminal subnucleus caudalis (TSC) following unilateral chronic constriction injury of the infraorbital nerve (IONL) as model of neuropathic pain. The rats were anesthetized and the left ION was exposed and tightly ligated with 6-0 silk suture. The ION- and sham-operated rats were left to survive for 7 days. The naive (n=3), ION- (n=3) and sham-operated (n=3) rats were perfused with Zamboni solution, brainstem was dissected, fixed overnight in the same fixative, and washed in 20% sucrose. Transverse cryostat sections were incubated with mouse monoclonal anti-OX42 antibody to identify microglia and/or simultaneously incubated with goat polyclonal antibody for TLR4. The corresponding secondary antibodies were conjugated with FITC and TRITC. The quantification was performed by image analysis system Lucia. An increased activation of microglia was observed bilaterally in the superficial lamina of TSC after unilateral IONL when compared with naive TSC. The microglia activation was lower in contralateral than ipsilateral TSC. The TSC of sham-operated rats displayed also mild increased OX42 immunofluorescence. In contrast to OX42, TLR4 immunostaining was found only in microglia of ipsilateral TSC from rats operated on unilateral IONL. Bilateral activation of microglia in TSC following unilateral IONL indicates a propagation of neuroinflammatory reaction to contralateral side. In contrast, upregulation of TLR4 suggests rather direct reaction to neuron injury in ipsilateral TSC.
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