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Alcohol does more than affect neurons. It also alters microglia, the brain’s immune cells, prompting them to break down the extracellular matrix that provides structural support for brain cells, according to a mouse study reported by ScienceAlert.
“For many years, alcohol’s effects on the brain have been viewed primarily through the lens of neurons, and for good reason: alcohol directly affects neuronal receptors,” said study senior author Dimitrios Davalos, a neuroscientist at Cleveland Clinic. “By observing microglia in real time, we were able to see that these cells do not simply respond to damage. They drive the harmful changes that alcohol causes in the brain.”
Microglia are specialized immune cells that constantly monitor the brain and help maintain its normal functioning. They detect threats, clear dead cells and damaged tissue, and modify neural connections.
To investigate how alcohol affects microglia, researchers conducted experiments on mice designed to mimic episodes of binge drinking. The animals received ethanol once or several times. Using two-photon microscopy and other imaging techniques, the scientists observed changes in microglia and neurons in living animals.
Within just one hour of alcohol exposure — before the sedative effects peaked — microglia showed significant changes in their shape and activity. The number and length of their branching processes decreased, reducing the area of the brain they could monitor. These changes became more pronounced after repeated alcohol exposure.
The researchers also observed microglia damaging the extracellular matrix, a network of structural molecules that supports brain cells and helps maintain stable connections between neurons. In mice exposed to alcohol, microglia began engulfing and digesting components of this matrix, weakening its structure.
According to the researchers, this process leads to the loss of synaptic connections, disrupting neuronal function and potentially helping explain alcohol’s sedative effects.
In related research, scientists studying the brain’s locus coeruleus in mice recently discovered an exceptionally long neuron, offering new insights into the mechanisms of learning.
