The Brain and Addiction

A recent study conducted by The Scripps Research Institute found for the first time that the compulsion to overeat, often leading to obesity, affects the same biological mechanism, the brain’s pleasure circuitry, that causes drug addictions to substances like cocaine and heroin. The study was published in the March 28th issue of Nature of Neuroscience.

According to Medical News Today, the study, which consisted of working with rats, confirmed what many obesity patients have been saying for years: that binging on junk food, like drug addiction, is very difficult to stop. The study showed “that as pleasure centers in the brain become less responsive, rats quickly develop compulsive overeating habits, eating increasing amounts of high-calorie, high-fat foods until they become obese.”

According to Medical News Today, this is the same progressively deteriorating chemical balance in reward brain circuits seen in rats that overconsume cocaine or heroin that is thought to lie behind the development of compulsive drug use.

“It presents the most thorough and compelling evidence that drug addiction and obesity are based on the same underlying neurobiological mechanisms,” said one of the researchers. “In the study, the animals completely lost control over their eating behavior, the primary hallmark of addiction.”

Those at risk seem to get caught in a cycle in which compulsive eating and substance abuse continue to hinder the recovery of either. Because there is evidence of the relationship between compulsive eating and drug addiction, hopefully the treatment for one will address the treatment of the other. Studies continue to show how addictive sugar and junk food are, especially for certain at-risk people. Individuals have reported that they often feel out of control when it comes to sugar and junk food. That they are unable to stop consuming these foods even after they become obese and have heath scares.

An international research team recently confirmed that the human need for stimulation and dopamine’s action upon the brain are connected. The study, which will soon appear in the leading scientific journal Proceedings of the National Academy of Sciences, revealed an explanation as to why people who constantly crave stimulation are in danger of addictive behavior such as drug abuse and gambling.

Though psychologists have known for years that ‘the urge to actively seek out new experiences’ is a personality trait, this is the first time scientists have been able to prove how this urge relates to hormonal activities in the brain. The study found that the hunger for stimulation is greater on average among people who possess more of the gratification hormone, dopamine, in the brain. (MedicalNewsToday.com) Dopamine, which is a key neurotransmitter in the reward pathway of the brain, plays an important role in our ability to handle stress, be motivated, and create an overall sense of well-being. The use of drugs or alcohol raises the level of dopamine, resulting in an artificial “feel-good” sensation. Chronic use of drugs or alcohol over-stimulates the receptors until they are damaged, unable to support themselves with their own chemicals, and the number of neurotransmitters is reduced. As a result, an individual will experience depression, anxiety, inability to handle stress, withdrawal symptoms, intense cravings, and deeper addiction.

The research team used PET scans and mapped the areas of the brain where dopamine was active among healthy individuals. Through measuring the levels of dopamine, the study found that individuals who had the strongest urge to seek out new and thrilling experiences had both more dopamine in the brain and more areas in the brain where dopamine was active. It’s understood that “if we make good decisions, our dopamine goes up. It tells our brain, you know, good call, that was the right move, you know, do that again next time, and it literally changes the anatomy of the brain. It strengthens certain connections. It decreases others.” (www.mcclatchydc.com) It becomes an issue in the fact that behavior that shouldn’t be repeated also releases dopamine. The study’s findings could prove to be valuable in possible strategies for substance abuse prevention.

In a recent study published in Proceedings of the National Academy of Sciences, researchers found an unexpected effect of the neurotransmitter (or signal substance) in the midbrain known as glutamate.

“We have found that a certain part of the brain’s reward system requires not only the signal substance dopamine, as was previously thought, but also glutamate,” said the director of the study at Uppsala University, Department of Neuroscience. Among many things, dopamine is important for the brain’s control of willed movements and the “reward system,” which provides humans with feelings of pleasure and happiness. The feeling is mediated by dopamine being released from nerve cells in the midbrain to the brain’s limbic system. The reward system is also affected by addictive drugs. Previous studies have shown nerve cells to “co-transmit” glutamate and dopamine, but science was unsure what this entailed for the the function of the brain.

To address this question, the researchers in the current study developed a special mouse model whose dopamine nerve cells lack the ability to both use and release glutamate. When they were treated with the dopamine-releasing substance amphetamine, a clear effect was observed. Normal mice responded, as expected, with increased activity and more stereotypical movements. On the other hand, the reaction in the model mice was significantly reduced, showing that a certain part of the reward system needs not only the signal substance dopamine, as was previously believed, but also glutamate. (PhysOrg.com)

“When we take away the glutamate,” the director said, “the brain’s reward system is numbed, which is extremely interesting.” Especially, in understanding how the reward system is formed and functions, as well as better understanding the diseases that affect it. “We hope our studies will ultimately provide relevant knowledge for an understanding of addiction mechanisms in humans.” The researchers will continue their study of the nerve cells involved to gain further insight into how important this system is for addiction.

According to new research from UCL Institute of Neurology, the release of the brain chemical dopamine influences how people make choices by affecting expectations of pleasure.

The study, which was recently published in Current Biology, confirms that dopamine not only plays an important role in how people make more complex decisions, but also how human expectations are formed. The study offers new insight into how pleasure expectation can go awry, such as with drug and alcohol addiction.

“Humans make much more complex decisions than other animals, such as which job to take or whether to start a family,” said the lead author of the study.  “We wanted to understand the role of dopamine in making these types of decisions.”

The role of the neurotransmitter dopamine in reward-seeking behavior is well understood through animal studies; however, its role in human behavior is much less understood. The results from the study indicate that when faced with having to consider options when making real-life decisions, dopamine did play a role in “signaling the expected pleasure from those possible future events.” (Science Daily). This signal is what humans use to make decisions. It makes sense that this is why the brain can get stuck in the pleasure-seeking cycle when drugs are involved.

A recent grant provided through the American Recovery and Reinvestment Act (AARA) awarded almost nine million dollars to the University of California San Diego. The brain study, which will use sophisticated gene-mapping tools and imaging technology to collect data about brain development in children, will be looking for the biological bases of differences in human behavior.

“The impact of the study is likely to be very broad,” said Terry Jernigan, Ph.D, project leader and professor at UC San Diego’s Center for Human Development. Jernigan hopes the brain study will accelerate the investigation of genetic risk factors and gene-by-environment interactions that contribute to disorders, such as substance abuse. “It will provide information that could help to enhance education, improve early detection of mental disorders, and identify targets for early interventions that may prevent negative outcomes, such as addiction and mental disorders.”

The brain study, which is called PING (pediatric imaging, neurocognition and genetics), would essentially create a database, or map, depicting the genomic landscape of the developing brain. The study will include 1,400 children between the ages of 3 and 20. The potential outcome of the study will make it possible to search for links between genetic variation and developing patterns of brain connectivity. It will shed light on how genes influence brain development and how it can go awry in certain individuals or following certain environmental events, making early intervention and prevention a more attainable goal.

The grant was awarded by the National Institute on Drug Abuse (NIDA), a part of the National Institutes of Health (NIH).

Our brains are hard-wired to seek reward. If we make a good decision, our dopamine levels go up. This tells our brain, good decision, do it again next time. It literally changes the anatomy of the brain to repeat the action. This strengthens certain connections and decreases others so that this desirable increase in dopamine will happen again. This is how an addiction is formed

Dopamine plays an important role in our ability to handle stress, be motivated, and create an overall sense of well-being. The use of drugs or alcohol raises the level of dopamine, resulting in an artificial “feel-good” sensation. When the brain’s levels of dopamine are in natural flux, we experience survival instincts: the need to eat, reproduce, or be a part of a group. In fact, our motivation to do anything: to feel good, to experience a sense of well-being, is controlled by the healthy fluctuation of dopamine levels. As a way of regulating itself, the body will also deactivate dopamine receptors, so that we don’t experience the need to eat or feel good all of the time. In doing this, the brain makes sure that the reward system that has enabled us to survive and evolve over millions of years is not disrupted.

However, chronic use of drugs or alcohol causes the brain to become accustomed to external stimulation of neurotransmitters and receptors. This interrupts the natural ebb and flow of the body’s chemical production. Chronic use over-stimulates the receptors until they are damaged, unable to support themselves with their own chemicals, and the number of neurotransmitters is reduced. As a result, an individual will experience depression, anxiety, inability to handle stress, withdrawal symptoms, intense cravings, and deeper addiction.

It isn’t just drug and alcohol addiction and dopamine that are related. Dopamine is thought to play a role in other conditions such as obesity, gambling, Parkinson’s disease and ADHD. The National Institute on Drug Abuse is researching different types of vaccines that will may eventually be able to prevent a drug, such as cocaine, from entering the brain and overloading the dopamine system and setting into motion a vicious cycle. Currently, protocols like Neurotransmitter Restoration address the re-balancing and repair of the brain and its reward cycle.