13 May 2024

A single exposure to alcohol was enough to trigger addiction

Even a single intoxication with ethanol leads to acute and persistent changes in the brain, reported German scientists from the University Hospital of Heidelberg and the Universities of Heidelberg and Cologne. In their experiments, alcohol in particular affected the balance of synapses and the dynamics of mitochondria in mice and fruit flies Drosophila melanogaster. This is described in a study published in the journal Proceedings of the National Academy of Sciences.

Excessive consumption of alcoholic beverages in youth is a risk factor for the formation of alcohol dependence in the future. In addition to personal problems, such a disorder is associated with brain damage, the development of dementia, cancer, trauma, liver problems, depression, increased risk of suicide and so on.

But what changes in the brain accompany the transition from sporadic to chronic alcohol use? The authors of most scientific papers have studied the effects of alcohol dependence on the hippocampus, a section of the brain's limbic system. However, the German researchers' goal was to identify lasting changes that could mediate the "memory" of ethanol exposure.

"We wanted to identify ethanol-dependent molecular changes. These lay the foundation for permanent cellular changes after a single acute ethanol intoxication. We studied the effects of a single ingestion of alcohol at the molecular, cellular and behavioural levels," the scientists said. Their hypothesis was that, similar to memory formation after a single lesson, even a single dose of ethanol can trigger the development of addiction.

To find neural molecular correlates of acute ethanol intoxication, they conducted experiments on mice and fruit flies. In the end, the changes caused by alcohol ingestion revealed firstly in the dynamics of mitochondria, which plays a role in the ability of hypothalamic neurons to control glucose levels and energy homeostasis in the body, and secondly in the balance between synapses, that is, the points of contact between two neurons.

"By imaging the brains of mice acutely exposed to ethanol, we found acute and long-lasting molecular, cellular and behavioural changes following a single ethanol intoxication in previously alcohol-free animals. Immunofluorescence analysis also revealed shortening of the initial segments of the axon (has higher excitability than other parts of the neuron. - Editor's note). <...> Taken together, our data suggest that a single exposure to ethanol induces changes that, in turn, may contribute to ethanol dependence," said the authors of the new paper.

The changes provoked by alcohol ingestion remained permanent, with ethanol abuse followed by relapse in mice and Drosophila at later ages.

According to the scientists, a similar cellular process occurs in humans, and the discovery of persistent changes due to a single exposure to ethanol is the first step towards understanding how taking small doses of alcohol at an early age can later turn into addiction.

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