The Unyielding Power of Dopamine

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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Thanks to global warming, the glacier has been retreating, so far removing two-thirds of its support for a steep mile-long slope, or scarp, containing perhaps 500 million cubic meters of material. (Think the Hoover Dam times several hundred.) The slope has been moving slowly since 1957, but scientists say it's become an avalanche waiting to happen, maybe within the next year, and likely within 20. When it does come crashing down into the fjord, it could set in motion a frightening tsunami overwhelming the fjord's normally peaceful waters .

"It could happen anytime, but the risk just goes way up as this glacier recedes," says hydrologist Anna Liljedahl of Woods Hole, one of the signatories to the letter.

The Barry Arm Fjord

Camping on the fjord's Black Sand Beach

Image source: Matt Zimmerman

The Barry Arm Fjord is a stretch of water between the Harriman Fjord and the Port Wills Fjord, located at the northwest corner of the well-known Prince William Sound. It's a beautiful area, home to a few hundred people supporting the local fishing industry, and it's also a popular destination for tourists — its Black Sand Beach is one of Alaska's most scenic — and cruise ships.

Not Alaska’s first watery rodeo, but likely the biggest

Image source: whrc.org

There have been at least two similar events in the state's recent history, though not on such a massive scale. On July 9, 1958, an earthquake nearby caused 40 million cubic yards of rock to suddenly slide 2,000 feet down into Lituya Bay, producing a tsunami whose peak waves reportedly reached 1,720 feet in height. By the time the wall of water reached the mouth of the bay, it was still 75 feet high. At Taan Fjord in 2015, a landslide caused a tsunami that crested at 600 feet. Both of these events thankfully occurred in sparsely populated areas, so few fatalities occurred.

The Barry Arm event will be larger than either of these by far.

"This is an enormous slope — the mass that could fail weighs over a billion tonnes," said geologist Dave Petley, speaking to Earther. "The internal structure of that rock mass, which will determine whether it collapses, is very complex. At the moment we don't know enough about it to be able to forecast its future behavior."

Outside of Alaska, on the west coast of Greenland, a landslide-produced tsunami towered 300 feet high, obliterating a fishing village in its path.

What the letter predicts for Barry Arm Fjord

Moving slowly at first...

Image source: whrc.org

"The effects would be especially severe near where the landslide enters the water at the head of Barry Arm. Additionally, areas of shallow water, or low-lying land near the shore, would be in danger even further from the source. A minor failure may not produce significant impacts beyond the inner parts of the fiord, while a complete failure could be destructive throughout Barry Arm, Harriman Fiord, and parts of Port Wells. Our initial results show complex impacts further from the landslide than Barry Arm, with over 30 foot waves in some distant bays, including Whittier."

The discovery of the impeding landslide began with an observation by the sister of geologist Hig Higman of Ground Truth, an organization in Seldovia, Alaska. Artist Valisa Higman was vacationing in the area and sent her brother some photos of worrying fractures she noticed in the slope, taken while she was on a boat cruising the fjord.

Higman confirmed his sister's hunch via available satellite imagery and, digging deeper, found that between 2009 and 2015 the slope had moved 600 feet downhill, leaving a prominent scar.

Ohio State's Chunli Dai unearthed a connection between the movement and the receding of the Barry Glacier. Comparison of the Barry Arm slope with other similar areas, combined with computer modeling of the possible resulting tsunamis, led to the publication of the group's letter.

While the full group of signatories from 14 organizations and institutions has only been working on the situation for a month, the implications were immediately clear. The signers include experts from Ohio State University, the University of Southern California, and the Anchorage and Fairbanks campuses of the University of Alaska.

Once informed of the open letter's contents, the Alaska's Department of Natural Resources immediately released a warning that "an increasingly likely landslide could generate a wave with devastating effects on fishermen and recreationalists."

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Image source: whrc.org

The obvious question is what can be done to prepare for the landslide and tsunami? For one thing, there's more to understand about the upcoming event, and the researchers lay out their plan in the letter:

"To inform and refine hazard mitigation efforts, we would like to pursue several lines of investigation: Detect changes in the slope that might forewarn of a landslide, better understand what could trigger a landslide, and refine tsunami model projections. By mapping the landslide and nearby terrain, both above and below sea level, we can more accurately determine the basic physical dimensions of the landslide. This can be paired with GPS and seismic measurements made over time to see how the slope responds to changes in the glacier and to events like rainstorms and earthquakes. Field and satellite data can support near-real time hazard monitoring, while computer models of landslide and tsunami scenarios can help identify specific places that are most at risk."

In the letter, the authors reached out to those living in and visiting the area, asking, "What specific questions are most important to you?" and "What could be done to reduce the danger to people who want to visit or work in Barry Arm?" They also invited locals to let them know about any changes, including even small rock-falls and landslides.

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