Abstract

Breathing, essential motor behavior for life, is generated by the respiratory pattern generator (RPG), a neural network distributed along the ventral (VRC) and dorsal (DRC) respiratory columns of the brainstem. The GPR is modulated by cells capable of detecting changes in CO2 and H+, located within the RPG or in nuclei that project towards it. Since microglia are cells that are functionally related to neurons and astrocytes, and these in turn, release substances able to activate microglia, we study whether the brainstem microglia of CF1 mice challenged with prolonged hypercapnia show phenotypic changes, both in vivo and in vitro, characteristic of a proinflammatory phenotype. The microglia morphology was evaluated in brains by using immunofluorescence for detecting Iba-1, a microglia marker, and the CD86 or CD206 membrane proteins, M1 and M2 microglia phenotype markers, respectively. Mice were exposure to 90 minutes of inhalation of pure air (controls) or air enriched with 10% CO2 for 30 minutes, followed by 60 minutes of pure air. In addition, pure cultures of brainstem microglia were exposed to 10% CO2 in air for 2 hours. In these cultures, detection of Iba-1, CD86, CD206 and the ELISA measurement of concentrations of IL-1β and TGF-β, cytokines released by microglial phenotype M1 and M2, respectively, were performed. We found that the microglia of brainstem chemosensitive nuclei, but not those from SP5 nuclei or cortex, reduce the number of branches, and increase the size of their cell bodies, associated with the increased expression of CD86, but not CD206. Besides, microglia exposed to high PCO2, release to the culture medium increased levels of IL-1β. Our results suggest that microglia may have a role during high PCO2 states, perhaps down-regulating the respiratory rhythm.