One drink often leads to two—and sometimes a whole lot more. Contrary to popular belief, this is not due to faulty willpower or lowered inhibitions, but rather a population of neurons in the vast neural substrate of your brain. That's what scientists at Texas A&M Health Science Center College of Medicine say they have discovered. They say alcohol changes the physical structure of certain neurons, creating a greater sensitivity to alcohol and a craving for more. This finding, published in the Journal of Neuroscience, could have major implications for the future treatment of alcoholism.
Using an animal model, researchers were able to distinguish between two types of dopamine receptors in the neurons, known as D1 and D2. Both types of neurons play a role in behavior and motivation. D1 is the “go” receptor, and D2 is the “halt” receptor. While it has been known for a long time that dopamine is involved in addiction, this study allowed researchers to see that D1 neurons become “excited” after periodic consumption of large amounts of alcohol, causing the brain to crave another drink to maintain that level of neural excitement. “If you drink alcohol, your brain will be changed in a way that makes you want to drink more,” says Dr. Jun Wang, lead researcher on the study.
Neurons are built like trees, with multiple "branches,” and on those branches are “spines”—the method by which neurons connect with one another. Dr. Wang tells mental_floss, “After alcohol consumption we found that neurons have grown more branches, and more spines.” This means drinking large quantities of alcohol literally increases your brain’s tolerance of, and desire for, more alcohol.
What’s especially interesting is how alcohol changes or “matures” the shape of the neural spines from a type known as “long-thin” to “mushroom” shaped, the latter of which store long-term memory. While it may seem counterintuitive that drinking more alcohol improves your memory, Dr. Wang says that it promotes a strengthened context-based memory. “It may not change your memory so that you will remember something better than other people; these memories will be associated with alcohol drinking specifically," he says. "If someone drinks alcohol in a bar, for example, he may remember that bar’s specific location better than someone else.” And the brain will also remember the amount of alcohol consumed and desire more of it.
In fact, when given a choice, the alcohol-consuming animals who had grown increased mushroom-shaped spines in their D1 neurons showed a greater preference for larger quantities of alcohol.
Bolstered by this information, the researchers then instilled an alcohol agonist—a drug that combines with the alcohol in the neuron’s receptors to reduce the excitability, and thus the craving. Rather than using an injection into the blood stream that would be delivered more diffusely all over the body, they injected the agonist directly into the brains of the animals to target the D1 neurons as specifically as possible. “We did observe a reduction in alcohol consumption,” says Dr. Wang. “It suggests that in the future we can target the D1 neurons and suppress alcohol consumption.”
While this may not provide a magic cure for alcoholism, Wang is certain that their research “opened the door and moved one essential step closer to finding the right therapeutics” to treat alcoholism.