Microglia regulate neuronal activity via structural remodeling of astrocytes

Area of Science:

• Neuroscience
• Cell Biology
• Physiology

Background:

• Neuron-glia interactions are crucial for synaptic transmission and neuronal excitability.
• Astrocytic structural plasticity is implicated in various physiological and pathological states, but its underlying mechanisms are unclear.

Purpose of the Study:

• To investigate the mechanism of structural astrocyte plasticity using the loss of astrocytic processes in the rat hypothalamus as a model.
• To elucidate the role of microglia in regulating astrocyte structure and neuronal activity.

Main Methods:

• Chronic high-salt diet administration in rats.
• Microscopic analysis of astrocytic processes and microglia in the hypothalamic magnocellular system.
• Assessment of synaptic glutamate clearance and NMDA receptor activation.
• Pharmacological inhibition of microglia-mediated astrocyte pruning.

Main Results:

• High-salt diet induced reactive microglia accumulation around vasopressin neurons.
• Microglia were observed to phagocytose (prune) astrocytic processes, reducing astrocyte coverage of neurons.
• Astrocyte pruning impaired glutamate clearance, leading to extrasynaptic NMDA receptor activation and increased vasopressin neuron activity.
• Inhibition of microglia-mediated pruning reduced neuronal activity and hypertension in high-salt fed rats.

Conclusions:

• Microglia actively regulate neuron-glia interactions by pruning astrocytic processes.
• This microglia-driven astrocyte pruning contributes to altered neuronal activity and hypertensive phenotypes.
• The study reveals a novel mechanism by which microglia modulate neuronal function and physiological states.