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Updated: Mar 18, 2026
Primary Microglia Isolation from Mixed Glial Cell Cultures of Neonatal Rat Brain Tissue
Published on: August 15, 2012
Microglial Contact Prevents Excess Depolarization and Rescues Neurons from Excitotoxicity
Go Kato1, Hiroyuki Inada1, Hiroaki Wake2
1Divison of Homeostatic Development, National Institute for Physiological Sciences, Okazaki 444-8585, Japan; Department of Physiological Sciences, The Graduate University for Advanced Studies, Okazaki 444-8585, Nishigo-naka, Myodaiji-cho, Japan.
Abstract:
Microglia survey and directly contact neurons in both healthy and damaged brain, but the mechanisms and functional consequences of these contacts are not yet fully elucidated. Combining two-photon imaging and patch clamping, we have developed an acute experimental model for studying the role of microglia in CNS excitotoxicity induced by neuronal hyperactivity. Our model allows us to simultaneously examine the effects of repetitive supramaximal stimulation on axonal morphology, neuronal membrane potential, and microglial migration, using cortical brain slices from Iba-1 eGFP mice. We demonstrate that microglia exert an acute and highly localized neuroprotective action under conditions of neuronal hyperactivity. Evoking repetitive action potentials in individual layer 2/3 pyramidal neurons elicited swelling of axons, but not dendrites, which was accompanied by a large, sustained depolarization of soma membrane potential. Microglial processes migrated to these swollen axons in a mechanism involving both ATP and glutamate release via volume-activated anion channels. This migration was followed by intensive microglial wrapping of affected axons and, in some cases, the removal of axonal debris that induced a rapid soma membrane repolarization back to resting potentials. When the microglial migration was pharmacologically blocked, the activity-induced depolarization continued until cell death ensued, demonstrating that the microglia-axon contact served to prevent pathological depolarization of the soma and maintain neuronal viability. This is a novel aspect of microglia surveillance: detecting, wrapping, and rescuing neuronal soma from damage due to excessive activity.
Insights
Microglia protect neurons from excitotoxicity by migrating to and wrapping swollen axons, preventing damaging depolarization and maintaining cell viability. This highlights a novel neuroprotective surveillance role for microglia.
Area of Science:
- Neuroscience
- Cell Biology
- Neuroimmunology
Background:
- Microglia interact with neurons in healthy and damaged brains, but the mechanisms and functional outcomes are not fully understood.
- Central nervous system (CNS) excitotoxicity from neuronal hyperactivity is a significant pathological process.
- The precise role of microglia in acute neuronal injury requires further elucidation.
Purpose of the Study:
- To investigate the role of microglia in CNS excitotoxicity induced by neuronal hyperactivity.
- To develop an experimental model for studying microglia-neuron interactions during acute neuronal damage.
- To elucidate the mechanisms and functional consequences of microglial contact with hyperactive neurons.
Main Methods:
- Developed an acute experimental model using two-photon imaging and patch clamping in cortical brain slices from Iba-1 eGFP mice.
- Simultaneously assessed axonal morphology, neuronal membrane potential, and microglial migration under repetitive supramaximal stimulation.
- Utilized pharmacological agents to block microglial migration.
Main Results:
- Neuronal hyperactivity induced axonal swelling and sustained soma membrane depolarization.
- Microglial processes migrated to swollen axons, involving ATP and glutamate release.
- Microglial wrapping of axons and debris removal led to soma repolarization and prevented cell death.
- Pharmacological blockade of microglial migration resulted in continued depolarization and neuronal death.
Conclusions:
- Microglia provide acute, localized neuroprotection against excitotoxicity.
- Microglia detect, wrap, and rescue neuronal soma from hyperactivity-induced damage.
- Microglia-axon contact is crucial for preventing pathological depolarization and maintaining neuronal viability.
