Dopamine is one of the key neurotransmitters - brain chemicals intimately involved in the reward/reinforcement response - which is so strongly tied to addictions … addictions of all kinds. A new report by Dr Nora Volkow, head of NIDA, focuses on the relationship between dopamine and addiction to food. We continue with a discussion of the functioning of dopamine and why it is so powerful in the addiction process.
HOWARD: Welcome to the CNS Podcast featuring Dr. Darryl Inaba, research director for CNS Productions, I am Howard La Mere. Some of the stories for this week include looking at personality types and the kinds of drugs they might use, and also how exercise effects your brain. But the first story that I think I want to talk about is a new report from Dr. Nora Volkow of NIDA, National Institute on Drug Abuse, that identifies dopamine as a culprit in food addiction. We've talked about dopamine often because it is one of the half dozen key brain chemicals involved in the addiction process, maybe one of the more dominant ones. What are your thoughts on food addiction in our overweight American society?
DARRYL: Howard, actually, it’s not anything new for Dr. Nora Volkow. I recall that when she first started working in neuroscience medicine, she was really interested in eating disorders, chronic overeating, binge eating disorder, pathological eating, also anorexia nervosa, anorexia bulimia and as she did more research and brain imaging she was so impressed with the amount of brain research that was going on with addictions that she sort of jumped ship and focused on all addictions. She now heads NIDA and has brought a greater understanding of addiction and cementing the notion throughout the whole United States that addiction is a chronic persistent brain disorder - that it is actually an illness and not willful miscontent or willful intent to harm. Addicts have a different active brain. After years of leading NIDA in that direction, Dr. Volkow is going back to her roots, so to speak, and concluding that this whole addiction thing seems to overlap with the food problems that she looked at in the beginning. And recently in an interview, she commented on her early work and compared food addiction, or disorders…eating disorders to cocaine addiction ...that the same chemical, neurotransmitter - dopamine - is involved in what she still calls the “reward/reinforcement center”, which I love to call the “survival reinforcement center”, in the subcortical limbic system of the brain ...operates in a dysfunctional way and in a hyperactive way when a food addict is exposed to excessive amounts of food like a cocaine addict when they take cocaine, in that the cravings are similar. I believe this has been known for a long time. I don’t know if the standard diagnostic manual in psychiatry is going to include eating disorders in addiction and related disorders. Right now, eating disorders have their own separate category, but based upon her work and the work of others, it is likely that it will be moved at some time into a subsegment or into a part of addictions and related disorders because it’s the same brain anomalies and the same brain differences that seem to be involved in people who are addicted to food or who are anorexic, or have other eating disorders. And from the early studies on genetics…from Maine and University of Texas, San Antonio, an ob (obese) gene was identified that was found in rats and mice that transmits a genetic tendency to be obese and overeat; not willfully overeating, but because that’s the way their genetics were wired and that is very much akin to addiction having a genetic component as well as a social component. It's an imbalance in the brain that brings about the behaviors that we recognize as binge eating disorders or pathological eating or chronic obesity as well drug – cocaine, heroin, alcohol addiction.
HOWARD: Let’s talk a little bit about dopamine here. I remember 20, 30 years ago, my favorite radio show was BBC World of Science. When the announcement of dopamine first…correct me if I’m getting my numbers wrong here, but it was like they had just discovered it or just sorted it out and it was fascinating to me then and it continues to be fascinating. So, you know, in the next video CNS is producing on opiates, you talk a lot about many of the key brain chemicals, but let’s focus a bit on dopamine because it is so powerful and important.
DARRYL: Dopamine actually was discovered long before we understood the powerful role it plays in all of our behaviors and all of our feelings. Dopamine is the major chemical that is produced from the very top of the brain…actually, it’s part of the brain stem, part of what we call the diencephalon that still exists, believe it or not, in lizards and snakes….
HOWARD: The old brain…the really old brain.
DARRYL: Yes, the older than old brain. It’s …its even sub subcortical…it’s below the limbic system and below the mammalian brain. It's part of the brain stem that evolved in reptiles and in amphibians after they’d moved from the sea. So, in a very old part of the brain, a ventral tegmental area in reptiles, in mammals and in humans produces a chemical dopamine from taurine diphenylamine and from tyrosine. Those are proteins from the food you eat. And it turns out that dopamine, …many people look at it as a pleasure chemical, as a reward chemical, but it’s a chemical that activates parts of the brain that influence behavior causing you to continue to expose yourself to something that gives you the dopamine effect in the brain. Sex increases dopamine. When you satisfy thirst, that releases dopamine saying you've satisfied thirst. Any drug that affects that part of the brain causes dopamine to be released and when you eat… you’re satisfying your hunger so dopamine is released. It is a reward saying, "you know, this is something good for you. This is something you got to keep doing." Now, there are differences in individuals and in certain animals in how much dopamine is produced, how much dopamine is released, or how many receptor sites and transporter mechanisms there are for dopamine, say in the nucleus accumbens septi, which in mammals is the “go” button. It’s the “more” button. You activate that with dopamine and you want more. We know that certain individuals who are prone toward addiction experience magnified dopamine activity in that part of the brain from alcohol, cocaine, any other drug, or say sex if it’s a process addiction, or food. It’s the activity is more exaggerated than a normie or somebody who doesn’t have a compulsive need to do those things. What’s interesting though is that the human brain evolved into a neocortex, a much larger thinking sentient brain that sits on top of the mammalian brain or the mesocortex that we share with all mammals which sits on top of the diencephalon, (which lizards and snakes and reptiles have) and that sits on top of the brain stem. So we’re looking at 4 different brain developments through evolution. But humans have the neocortex or the conscious brain…the judgmental brain that can weigh positives and benefits and make decisions based upon that - it’s that same chemical, dopamine, that is released from the ventral tegmental area…or primitive diencephalon brain…it’s that same chemical that activates the “go” switch in the mesocortex…the nucleus accumbens….dopamine is the same chemical activates the orbital prefrontal cortex where the “stop” switch is located. In a normal individual, once it’s activated, it turns off the go switch. So it weighs the benefits of using cocaine or the benefits you’re getting from the food you’re eating, and there is a control mechanism that says, you know, that’s really good. You need to eat, but if you eat too much, it’s not going to be good for you so it turns off that hunger…it turns off the food reward. But, addicts have an overactive "go" button, and their overactive unconscious brain tells them to do this more and more. Their "stop switch", on the other hand - is underactive or inactive so it gets stuck on “on” and they continue to expose themselves to drugs or in this case, food, despite negative consequences, despite morbid obesity despite the fact that they don’t feel good about how they look or how they feel when they overeat. They have lost the ability to stop that signal.
HOWARD: Does the body increase… dopamine production or is it a change in the receptors that happens? Question #1. Question #2 – did you just say that the stop switch is also controlled by dopamine production or activation?
DARRYL: …we’ll start with question #2. The same neurochemical that activates the go switch, which is dopamine, also activates the stop switch, so…
HOWARD: That’s interesting and contradictory.
DARRYL: Well, no, …it’s how the brain does its checks and balances in order to keep the person in a homeostasis or "even balance" People must eat to survive. If you don’t eat, you’re not going to survive, so the brain creates a cravings for food and you respond by putting food into your system, which releases dopamine - it’s the reward chemical or survival chemical that tells you…or unconsciously tells you that this is good. You’ve got to do this. That’s great you did it...you satisfied that craving or need and now you should stop. The "stop switch" is part of the same system, once activated, the stop switch sends its message back through these fibers… it sends back another chemical called glutamate and glutamate interacts with GABA on the stop switch and there is interaction with norepinepherine and also with endorphins - and that action is the way that the "stop switch" turns off the "go switch." Now the other question was...what was your other question, Howard?
HOWARD: Does the dopamine production change …or do the receptors change?
DARRYL: That’s actually a good question, because researchers are finding that there are a myriad of adaptations that the brain goes through. The brain is plastic…it’s such a pliable thing that in the face of exposures to different types of concentrations, it adapts and it changes. We often speak about it as allostasis ... an adaptation of the brain that produces an imbalanced state that must be brought back in balance in order for a person to function. And in the case of dopamine, although there is initially a greater amount of dopamine released with any action that is potentially addictive - whether it’s triggered by food or drugs or behaviors or anything else, that high release causes a depletion...there’s actually less and less dopamine in the brain and so the craving or the compulsion to feel like you’ve satisfied the need to eat, satisfy a sexual drive, satisfy basic functionality becomes a tremendous craving – what we call endogenous craving - when a person’s brain no longer has any dopamine activity to speak of - which is necessary to make them feel like they’re functioning correctly. This occurs because of many things. When an excessive amount of dopamine stimulus enters the body the brain stops producing dopamine and/or inhibits its release so you don’t get any activity. And it can also sort of stimulate enzymes and metabolism systems so that the dopamine you do have is broken down even faster so that it doesn't have much of an effect. But there are also receptor site changes as you mentioned - that is correct. We see what is called up regulation and down regulation of receptor sites meaning that if the brain has too much dopamine, then the receptor sites are sucked back into their dendritic membranes so that they can’t be activated and when dopamine is depleted, those same receptor sites get shoved up to the surface again so they can interact with whatever dopamine is available. There are transporter mechanisms. In the axons that …release dopamine, there are little suction cups or little paddlewheels that once the dopamine is released from the synaptic vesicles that are in the brain, …these transporters spit them out into the synaptic gap so that they can operate and then once they cause a synapse (to fire), they suck them back in. They… sort of transport them back into the brain to be stored again. Well, what happens in one of the adaptations is the transporter mechanisms actually wither away and are gone ... with a cocaine addiction or a methamphetamine addiction, close to 25% of the transporter mechanisms are wiped out during the addictive use of those drugs. So, there are many, many different processes that causes a deregulation or an imbalance or an allostasis of dopamine activity in the brain, which translates into a craving or a need to continue doing behaviors to produce as much dopamine as possible - but the more you do of those behaviors, the less dopamine is produced - it's an endless cycle, and that’s part of the addiction.
HOWARD: I think this is what is called “Catch 22”.
HOWARD: Well…we didn’t talk too much about food here, but I think this is time well spent - to get a better understanding of this particular brain chemical, dopamine, and what it does. So, I’m glad we did that.
DARRYL: Well, you know what’s important for me, Howard, is that we’re finally hoping…I’m just praying that we can start to erode the stigma placed on addicts - it would help them resolve the tremendous guilt and shame…tremendous lack of pride they have in who they are because of how we have treated addicts...we don't treat those with diabetes or hypertension…with the same stigma that occurs with people with eating disorders. You see somebody who is obese and the immediate thought of most people is that person is a glutton, that person just cannot control their cheeseburger urges because they just love to eat and cannot stop eating because they’re just stupid or crazy. Now that we understand about brain differences…genetic and otherwise, that occur in addiction - including eating disorders, hopefully we can start to unravel the stigma and help people get better treatments that maintain better health for them.
HOWARD: Fascinating. Fascinating the leaps we’ve made in our understanding of science in the form of the way the brain functions and again, controls the body and controls our behaviors. Anyway, we’re out of time for today, so… thanks to all the listeners for joining us. Check back soon and if you have comments, questions, or suggestions, we would love to hear from you.