How can alcohol change your life

Alcohol changes the spaces between cells in the brain

If you drink too often and too much alcohol, you not only risk your health, but also an addiction. But what happens in the brain is still unclear. Now researchers have discovered a previously unknown effect of alcohol on our brains. Accordingly, even moderate but prolonged consumption of alcohol changes the structure of the intercellular spaces in the gray matter of the brain. They become more permeable and thus addiction-promoting messenger substances such as dopamine can be better distributed in the brain. According to the scientists, this effect could explain why alcohol, despite weak acute influences on our reward system, can become addictive over time.

A glass in honor ... The consumption of beer, wine or other alcoholic beverages is simply part of the process for many people. After work, they go out for a drink with colleagues or friends or relax on the sofa with a glass of wine. The only problem: Even moderate, but regular consumption of alcohol can lead to habituation in the long run and gradually turn into an addiction. "Alcohol has the ability to trigger neurological adaptations that encourage the formation of strong consumption habits and addiction and therefore often lead to alcoholism," explain Silvia De Santis of the Spanish University of Miguel Hernández and her colleagues. However, drinking alcohol triggers a far less powerful reaction in the reward system than other drugs. “How alcohol develops its potent addictive effect is a mystery that has not yet been understood,” the researchers say.

Searching for clues in the extracellular space

De Santis and her team have now investigated a possible cause in more detail: changes in the gray matter of the brain that could possibly influence the concentration and spread of the neurotransmitter dopamine. Dopamine plays a crucial role in the reward system and is responsible, among other things, for the happiness and satisfaction addicts feel when quenching their addiction. It is known from studies that this neurotransmitter is not only transmitted at the synapses between nerve cells, but is also distributed between the cells via diffusion processes. “Increased diffusion in the extracellular space may appear to be very unspecific mechanisms of action for a drug. However, this influences a large number of communication processes in the brain, ”explains co-author Wolfgang Sommer from the Central Institute for Mental Health in Mannheim. The extracellular space consists of fluid-filled cavities and tubules that form between brain cells and their many processes.

De Santis, Sommer and their colleagues have now investigated whether and how these cell spaces change due to continued alcohol consumption in people with chronic alcoholism and in rats after one month of regular alcohol consumption. Using diffusion tensor imaging, a variant of magnetic resonance tomography, they recorded how well water molecules were distributed in the extracellular space of the brains of the animal and human subjects. In addition, they used a contrast agent to determine how the structure of the cell spaces differed between the alcohol-dependent rats and healthy control animals.

Stronger diffusion facilitates the spread of dopamine

The investigations showed clear differences: “Our results show a far-reaching increase in diffusion in the gray matter of the brain in both the alcohol-drinking animals and the alcoholic patients,” report De Santis and her colleagues. “As far as we know, this is the first time that diffusion changes in the brain of alcoholics have been examined and determined.” At the same time, the structure of the extracellular space and the microglial cells that influence its shape changed: “After chronic exposure to alcohol, these immune cells in the brain react and shrink and withdraw their dense network of appendages, ”reports De Santis' colleague Santiago Canals. "The removal of barriers changes the geometry of the extracellular space and new diffusion pathways arise." This means that dopamine can also spread more strongly in the brain as a result.

In the opinion of the scientists, their results provide an explanation for why alcohol consumption can lead to addiction over time, despite its rather weak acute effects on the reward system: The structure and shape of the cell spaces in the brain that have been changed by alcohol make it easier for dopamine to spread, and thus also increase their concentration and effect on different brain regions. "The increased neurotransmitter concentration over time, combined with a slower breakdown at the synapses, could help turn the rather weakly rewarding properties of alcohol into the powerful habituation effect that leads some people into addiction," they state Researcher. If this theory is confirmed, it could potentially also help develop better preventive and countermeasures against alcohol addiction.

Source: Silvia De Santis (Universidad Miguel Hernández, Spain) et al., Science Advances, doi: 10.1126 / sciadv.aba0154

June 30, 2020

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