The Unyielding Power of Dopamine
Nora D. Volkow, M.D., became Director of the National Institute on Drug Abuse (NIDA) at the National Institutes of Health in May 2003. NIDA supports most of the world's research on the health aspects of drug abuse and addiction.
Dr. Volkow's work has been instrumental in demonstrating that drug addiction is a disease of the human brain. As a research psychiatrist and scientist, Dr. Volkow pioneered the use of brain imaging to investigate the toxic effects of drugs and their addictive properties. Her studies have documented changes in the dopamine system affecting the actions of frontal brain regions involved with motivation, drive, and pleasure and the decline of brain dopamine function with age. She has also made important contributions to the neurobiology of obesity, ADHD, and the behavioral changes that occur with aging.
Question: What makes dopamine such a powerful chemical?
Nora Volkow: Dopamine is a chemical substance that serves to send messages between two cells in the brain, and that's, we call neurotransmitters. There are many neurotransmitters and dopamine plays a key role in the areas of the brain that enable a wide variety of functions, best known is movement and when your dopamine cells die, for example, you cannot initiate movement, and that's Parkinson's disease.
But the effects of dopamine go way beyond movement and one of actions, very relevant for drug abuse and addiction, is it modulates the areas of the brain involved with our ability to perceive reward reinforcement and to be motivated by that reward to do actions. So, for example, it's so important that if you can generate through trans-genetic, genetic technologies, you can generate in a mouse that does produce synthesized dopamine. These animals will die of starvation because they don't have the motivation to engage in the behaviors to go and eat the food. You can rescue this animal by injecting dopamine into the areas of the brain that control this. But if you don't to that, these animals will die of starvation. And that really epitomizes how extraordinary important dopamine is. It gives you that energy, that drive to do things.
Now, drugs of abuse, we know that for the past 50 years, all of them, whether it's legal or illegal, they don't make any distinctions over there in terms of the pharmacology, they increase dopamine in specific areas of the brain, of the limbic brain. And this ability to increase dopamine when a person takes a drug is associated directly with what we call rewarding or reinforcing effects. So if you can actually manipulate it in such a way that to interfere with the ability of a drug to increase dopamine, than that drug is no longer pleasurable.
And so that's why dopamine is so important. Understanding why certain drugs can produce addiction and others not. If a drug produces increases in dopamine in these limbic areas of the brain, then your brain is going to understand that signal as something that is very reinforcing. And will learn it very rapidly, and so that the next time you get exposed to that stimuli, your brain already has learned that that's reinforcing and you immediately what we call a type of memory that's conditioning, will desire that particular drug.
Now, these mechanisms are not developed in our brains to take drugs. These mechanisms of dopamine signal reinforcement and once you have experienced it, getting conditioned to it is extraordinary important way for nature to ensure that humans, as well as animals, will perform behaviors that are indispensable for survival. So therefore, it shouldn't surprise us that behaviors such as eating or sexual behavior are linked with increases in dopamine and in the same areas that drugs do it. There are differences though, because natural reinforcers increase dopamine as a function very much of the context. What do I mean by that? If you're hungry, for example, and you get exposed to food, that will increase dopamine much more than if you just finished eating. And so as you eat, the ability of food to increase dopamine goes down and eventually disappears. And because it disappears, you are no longer motivated to eat the food.
Question: How is dopamine related to drug addiction?
Nora Volkow: What happens with drugs though, on the other hand, is they do not decline the ability to increase dopamine. So a person may take a hit of cocaine, snort it, it increases dopamine, takes a second, it increases dopamine, third, fourth, fifth, sixth. So there's never that decrease that ultimately leads to the satiety. And this is believed that then these differences between the normal responses of the dopamine stimuli as it was developed through evolution to serve physiological functions, versus the ways that drugs do it, much more potently, longer duration of action. And it does not decline with repeated administration. It's believed to trigger the adaptations, the plastic changes in our brain, that eventually will lead, in those individuals that are vulnerable, to addiction. To the process of addiction, which is a condition whereupon the person, with repeated administration of drugs, no longer can control his or her ability to decide when they take or they don't take the drug. This is fundamentally a stage where that individual has lost control and has intense drive to compulsively take the drug.
And that's what we call addiction. Not everybody that takes drugs, actually, becomes addicted. We've come to recognize, for example, that approximately 50% of the vulnerability of a person to take, to become addicted is genetically determined. So that vulnerability has a very strong genetic component. It also has other processes that determine vulnerabilities. For example, if you get exposed to drugs when you're very young, very early adolescence, you're much more likely to become addicted than if you get exposed to the same drugs when you're an adult. And this has to do with the fact that the adolescent brain is much more neuroplastic than the adult brain. And as a result of that, a drug, which triggers this adaptation process, is likely to produce these changes faster in an adolescent and it's also the duration of those changes is likely to be much longer lasting in an adolescent than it is an adult. So these are two processes as it relates to addiction.
Recorded on November 6, 2009
Drug addiction researcher Nora Volkow walks us through the singular chemical that drives substance abuse.
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Water may be far more abundant on the lunar surface than previously thought.
- Scientists have long thought that water exists on the lunar surface, but it wasn't until 2018 that ice was first discovered on the moon.
- A study published Monday used NASA's Stratospheric Observatory for Infrared Astronomy to confirm the presence of molecular water..
- A second study suggests that shadowy regions on the lunar surface may also contain more ice than previously thought.
Credits: NASA/Daniel Rutter<p>Still, it's not as if the moon is dripping wet. The observations suggest that a cubic meter of the lunar surface (in the Clavius crater site, at least) contains water in concentrations of 100 to 412 parts per million. That's roughly equivalent to a 12-ounce bottle of water. In comparison, the same plot of land in the Sahara desert contains about 100 times more water.</p><p>But a second study suggests other parts of the lunar surface also contain water — and potentially lots of it. Also publishing their findings in <a href="https://www.nature.com/articles/s41550-020-1198-9#_blank" target="_blank">Nature Astronomy</a> on Monday, the researchers used the Lunar Reconnaissance Orbiter to study "cold traps" near the moon's polar regions. These areas of the lunar surface are permanently covered in shadows. In fact, about 0.15 percent of the lunar surface is permanently shadowed, and it's here that water could remain frozen for millions of years.</p><p>Some of these permanently shadowed regions are huge, extending more than a kilometer wide. But others span just 1 cm. These smaller "micro cold traps" are much more abundant than previously thought, and they're spread out across more regions of the lunar surface, according to the new research.</p>
Credit: dottedyeti via AdobeStock<p>Still, the second study didn't confirm that ice is embedded in micro cold traps. But if there is, it would mean that water would be much more accessible to astronauts, considering they wouldn't have to travel into deep, shadowy craters to extract water.</p><p>Greater accessibility to water would not only make it easier for astronauts to get drinking water, but could also enable them to generate rocket fuel and power.</p><p style="margin-left: 20px;">"Water is a valuable resource, for both scientific purposes and for use by our explorers," said Jacob Bleacher, chief exploration scientist in the advanced exploration systems division for NASA's Human Exploration and Operations Mission Directorate, in a statement. "If we can use the resources at the Moon, then we can carry less water and more equipment to help enable new scientific discoveries."</p>
A study finds 1.8 billion trees and shrubs in the Sahara desert.
- AI analysis of satellite images sees trees and shrubs where human eyes can't.
- At the western edge of the Sahara is more significant vegetation than previously suspected.
- Machine learning trained to recognize trees completed the detailed study in hours.
Why this matters<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDU2MDQ1OC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYzOTkyODg5NX0.O3S2DRTyAxh-JZqxGKj9KkC6ndZAloEh4hKhpcyeFDQ/img.jpg?width=980" id="3770d" class="rm-shortcode" data-rm-shortcode-id="3c27b79d4c0600fb6ebb82e650cabec0" data-rm-shortcode-name="rebelmouse-image" />
Area in which trees were located
Credit: University of Copenhagen<p>As important as trees are in fighting climate change, scientists need to know what trees there are, and where, and the study's finding represents a significant addition to the global tree inventory.</p><p>The vegetation Brandt and his colleagues have identified is in the Western Sahara, a region of about 1.3 million square kilometers that includes the desert, <a href="https://en.wikipedia.org/wiki/Sahel" target="_blank">the Sahel</a>, and the <a href="https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/subhumid-zones" target="_blank" rel="noopener noreferrer">sub-humid zones</a> of West Africa.</p><p>These trees and shrubs have been left out of previous tabulations of carbon-processing worldwide forests. Says Brandt, "Trees outside of forested areas are usually not included in climate models, and we know very little about their carbon stocks. They are basically a white spot on maps and an unknown component in the global carbon cycle."</p><p>In addition to being valuable climate-change information, the research can help facilitate strategic development of the region in which the vegetation grows due to a greater understanding of local ecosystems.</p>
Trained for trees<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDU2MDQ3MC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYzNTk5NTI3NH0.fR-n1I2DHBIRPLvXv4g0PVM8ciZwSLWorBUUw2wc-Vk/img.jpg?width=980" id="e02c0" class="rm-shortcode" data-rm-shortcode-id="79955b13661dca8b6e19007935129af1" data-rm-shortcode-name="rebelmouse-image" />
Credit: Martin Brandt/University of Copenhagen<p>There's been an assumption that there's hardly enough vegetation outside of forested areas to be worth counting in areas such as this one. As a result the study represents the first time a significant number of trees — likely in the hundreds of millions when shrubs are subtracted from the overall figure — have been catalogued in the drylands region.</p><p>Members of the university's Department of Computer Science trained a machine-learning module to recognize trees by feeding it thousands of pictures of them. This training left the AI be capable of spotting trees in the tiny details of satellite images supplied by NASA. The task took the AI just hours — it would take a human years to perform an equivalent analysis.</p><p>"This technology has enormous potential when it comes to documenting changes on a global scale and ultimately, in contributing towards global climate goals," says co-author Christian Igel. "It is a motivation for us to develop this type of beneficial artificial intelligence."</p><p>"Indeed," says Brandt says, "I think it marks the beginning of a new scientific era."</p>
Looking ahead and beyond<p>The researchers hope to further refine their AI to provide a more detailed accounting of the trees it identifies in satellite photos.</p><p>The study's senior author, Rasmus Fensholt, says, "we are also interested in using satellites to determine tree species, as tree types are significant in relation to their value to local populations who use wood resources as part of their livelihoods. Trees and their fruit are consumed by both livestock and humans, and when preserved in the fields, trees have a positive effect on crop yields because they improve the balance of water and nutrients."</p><p>Ahead is an expansion of the team's tree hunt to a larger area of Africa, with the long-term goal being the creation of a more comprehensive and accurate global database of trees that grow beyond the boundaries of forests.</p>
Tea and coffee have known health benefits, but now we know they can work together.
Credit: NIKOLAY OSMACHKO from Pexels
- A new study finds drinking large amounts of coffee and tea lowers the risk of death in some adults by nearly two thirds.
- This is the first study to suggest the known benefits of these drinks are additive.
- The findings are great, but only directly apply to certain people.