Related Experiment Video
Updated: Feb 19, 2026
Simultaneous Imaging of Microglial Dynamics and Neuronal Activity in Awake Mice
Published on: August 23, 2022
Microglia are continuously activated in the circumventricular organs of mouse brain
Shohei Takagi1, Eriko Furube1, Yousuke Nakano2
1Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan.
Abstract:
Microglia are the primary resident immune cells of the brain parenchyma and transform into the amoeboid form in the "activated state" under pathological conditions from the ramified form in the "resting state" under physiologically healthy conditions. In the present study, we found that microglia in the circumventricular organs (CVOs) of adult mice displayed the amoeboid form with fewer branched cellular processes even under normal conditions; however, those in other brain regions showed the ramified form, which is characterized by well-branched and dendritic cellular processes. Moreover, microglia in the CVOs showed the strong protein expression of the M1 markers CD16/32 and CD86 and M2 markers CD206 and Ym1 without any pathological stimulation. Thus, the present results indicate that microglia in the CVOs of adult mice are morphologically and functionally activated under normal conditions, possibly due to the specialized features of the CVOs, namely, the entry of blood-derived molecules into parenchyma through fenestrated capillaries and the presence of neural stem cells.
Insights
Microglia in the brain's circumventricular organs (CVOs) are activated in their amoeboid form even in healthy mice. This suggests unique CVO features drive immune cell activation under normal physiological conditions.
Area of Science:
- Neuroimmunology
- Brain Immune Cell Biology
Background:
- Microglia, the brain's resident immune cells, typically exist in a resting, ramified state under normal conditions.
- Under pathological conditions, microglia transform into an activated, amoeboid form with reduced cellular processes.
Purpose of the Study:
- To investigate the morphological and functional state of microglia within the circumventricular organs (CVOs) of adult mice under normal physiological conditions.
- To compare microglia in CVOs with those in other brain regions.
Main Methods:
- Morphological analysis of microglia in adult mouse CVOs and other brain regions.
- Assessment of M1 (CD16/32, CD86) and M2 (CD206, Ym1) marker protein expression in CVO microglia.
Main Results:
- Microglia in CVOs exhibited an amoeboid morphology with fewer branched processes, unlike the ramified microglia found in other brain areas.
- CVO microglia displayed strong expression of both M1 and M2 activation markers (CD16/32, CD86, CD206, Ym1) without any pathological stimulus.
- These findings indicate a state of constitutive activation in CVO microglia.
Conclusions:
- Microglia in the circumventricular organs of adult mice are morphologically and functionally activated under normal conditions.
- Specialized CVO features, including fenestrated capillaries allowing blood-borne molecule entry and the presence of neural stem cells, likely contribute to this constitutive activation.
More Related Videos
12:48In Vivo Dynamics of Retinal Microglial Activation During Neurodegeneration: Confocal Ophthalmoscopic Imaging and Cell Morphometry in Mouse Glaucoma
Published on: May 11, 2015
09:12Isolation of Cortical Microglia with Preserved Immunophenotype and Functionality From Murine Neonates
Published on: January 30, 2014