Those who have studied or treated addiction would no doubt agree it almost always plays out as a complex dance between biology and human behavior. Indeed, the most successful treatment approaches almost always target both the physiological underpinnings of a chronic illness and the harmful, self-defeating behaviors that keep people stuck in a negative spiral.
Yet, as advances continue in neuroscience, evidence showing that alcoholics and addicts are typically “wired” differently than their peers, and that consistent and excessive use of substances significantly alters their brains’ capacity to escape compulsion and “do the next right thing” when it comes to using, continues to mount. A new study, conducted by researchers at the Texas A&M Health Science Center College of Medicine, offers some new insights that strengthen an appreciation for a scientific explanation of addictive behaviors. Many either “go” or “stop” when it comes to drinking and other addictive behaviors, they say, because certain neurons in their brains are consistently stronger in the fight to control impulses.
Previous research has shown that alcohol consumption substantially alters the physical structure and function of key neurons in the region of the brain responsible for stimulus-response learning and reward-reinforcement behavior. When activated, one type of neuron in particular — D1 neurons —pretty consistently prime the brain to want to progress from one drink, to two, and more. Essentially, these D1 neurons tell us to “go” forward with drinking or other behaviors that produce dopamine. Now, they’ve discovered the neurons that can tell us to stop — and how the two relate to one another.
Scientists often describe neurons in the brain as resembling a tree, with many branches coming off of them. Each neuron has one of two types of dopamine receptors — D1 or D2. Because they stimulate the pursuit of dopamine, D1 neurons are considered part of a “go” pathway in the brain, while D2 neurons constitute a “no-go” pathway. In other words, when D2 neurons are activated, they discourage action — telling you to wait, to stop, to do nothing.
“At least from the addiction point of view, D2 neurons are good,” said Jun Wang, MD, PhD, the lead author of this latest study and assistant professor in the Department of Neuroscience at the Texas A&M. “When they are activated, they inhibit drinking behavior, and therefore activating them is important for preventing problem drinking …”
The trouble is, even in individuals without alcoholism, D2 neurons tend to become deactivated when we drink too much. This deactivation means there is nothing telling us to stop drinking, so we drink more, in a self-perpetuating cycle.
The researchers found that in animal models, repeated cycles of excessive alcohol intake, followed by abstaining from alcohol, actually changed the strength of neuronal connections, making D2 signals less powerful — and making it more natural and likely for individuals to seek alcohol. “Think of the binge drinking behavior of so many young adults,” Wang said. “Essentially they are probably doing the same thing that we’ve shown leads to inhibition of these so-called ‘good’ neurons and contribute to greater alcohol consumption.”
These findings provide insight into another mechanism underlying the complicated disease called alcoholism. When it comes to alcohol consumption, the study notes, we have now come to understand that “go” and “no go” neural pathways have an opposing role, where one is chemically bound to win out.
By manipulating the activity of these neurons, the researchers were actually able to change the alcohol-drinking behavior of animals that had been “trained” to seek alcohol, and the more the D2 neurons are activated, the greater the effect is likely to be.
Although the researchers warn that it will take a while to test these findings in humans, the findings thus far provide reason to be optimistic. If we can find practical ways of stimulating D2 neurons in people, then we might one day be able to prevent alcoholics from wanting another drink. “That’s the ultimate goal,” Wang said. “I hope these findings will eventually be able to be used for treatment for alcohol addiction.” And that’s good news for any of us close to someone who struggles…