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Article

Microglia and Inhibitory Circuitry in the Medullary Dorsal Horn: Laminar and Time-Dependent Changes in a Trigeminal Model of Neuropathic Pain

1
Department of Anatomy, Histology and Neuroscience, Medical School, Autónoma University of Madrid, 28029 Madrid, Spain
2
Ph.D. Programme in Neuroscience, Doctoral School, Autónoma University of Madrid, 28049 Madrid, Spain
3
Departamento de Anatomía, Facultad de Medicina, Universidad Francisco de Vitoria, Pozuelo de Alarcón, 28223 Madrid, Spain
4
Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, 28049 Madrid, Spain
*
Author to whom correspondence should be addressed.
These authors contributed equally to this study.
Academic Editor: Man-Kyo Chung
Int. J. Mol. Sci. 2021, 22(9), 4564; https://doi.org/10.3390/ijms22094564
Received: 4 March 2021 / Revised: 22 April 2021 / Accepted: 22 April 2021 / Published: 27 April 2021
(This article belongs to the Special Issue Neurobiological Mechanisms of Orofacial Chronic Pain)
Craniofacial neuropathic pain affects millions of people worldwide and is often difficult to treat. Two key mechanisms underlying this condition are a loss of the negative control exerted by inhibitory interneurons and an early microglial reaction. Basic features of these mechanisms, however, are still poorly understood. Using the chronic constriction injury of the infraorbital nerve (CCI-IoN) model of neuropathic pain in mice, we have examined the changes in the expression of GAD, the synthetic enzyme of GABA, and GlyT2, the membrane transporter of glycine, as well as the microgliosis that occur at early (5 days) and late (21 days) stages post-CCI in the medullary and upper spinal dorsal horn. Our results show that CCI-IoN induces a down-regulation of GAD at both postinjury survival times, uniformly across the superficial laminae. The expression of GlyT2 showed a more discrete and heterogeneous reduction due to the basal presence in lamina III of ‘patches’ of higher expression, interspersed within a less immunoreactive ‘matrix’, which showed a more substantial reduction in the expression of GlyT2. These patches coincided with foci lacking any perceptible microglial reaction, which stood out against a more diffuse area of strong microgliosis. These findings may provide clues to better understand the neural mechanisms underlying allodynia in neuropathic pain syndromes. View Full-Text
Keywords: chronic pain; allodynia; trigeminocervical complex; glycine transporters chronic pain; allodynia; trigeminocervical complex; glycine transporters
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MDPI and ACS Style

García-Magro, N.; Martin, Y.B.; Negredo, P.; Zafra, F.; Avendaño, C. Microglia and Inhibitory Circuitry in the Medullary Dorsal Horn: Laminar and Time-Dependent Changes in a Trigeminal Model of Neuropathic Pain. Int. J. Mol. Sci. 2021, 22, 4564. https://doi.org/10.3390/ijms22094564

AMA Style

García-Magro N, Martin YB, Negredo P, Zafra F, Avendaño C. Microglia and Inhibitory Circuitry in the Medullary Dorsal Horn: Laminar and Time-Dependent Changes in a Trigeminal Model of Neuropathic Pain. International Journal of Molecular Sciences. 2021; 22(9):4564. https://doi.org/10.3390/ijms22094564

Chicago/Turabian Style

García-Magro, Nuria, Yasmina B. Martin, Pilar Negredo, Francisco Zafra, and Carlos Avendaño. 2021. "Microglia and Inhibitory Circuitry in the Medullary Dorsal Horn: Laminar and Time-Dependent Changes in a Trigeminal Model of Neuropathic Pain" International Journal of Molecular Sciences 22, no. 9: 4564. https://doi.org/10.3390/ijms22094564

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