Mice That Resist Cocaine Addiction

Mice That Resist Cocaine Addiction

This week on SciShow News, scientists have
taken some steps to solve a couple genetic mysteries: why birds lay eggs, and the biology
of addiction. Giving birth to live young, called viviparity,
is a pretty sweet evolutionary strategy. It seems to be helpful in colder environments,
and predators might gobble up eggs more easily than little scampering offspring. Lots of vertebrates give birth to live animals,
including most mammals and a number of snakes and lizards. But there’s one huge exception: birds, and
the larger group they belong to, called archosauromorphs, which also includes crocodiles and some dinosaurs. Until this week, we thought all these creatures
had always laid eggs. Maybe because of some genetic reason that
prevented viviparity. But according to a new study published in
the journal Nature Communications, we were wrong The study is about an archosauromorph called
Dinocephalosaurus, a marine reptile dating back to the Triassic period. It’s a primitive member of the group, only
distantly related to crocodiles or birds. But these researchers think that it gave birth
to live young. As evidence, they present a fossil from around
245 million years ago with an embryo clearly preserved inside of it. The tiny bones look like a mini-adult. There was no sign of fossilized calcium material
from an eggshell, so it probably wasn’t in an egg. And the researchers know it’s not something
the adult specimen ate, because it’s in the wrong position to be food. It’s facing with its head forward, while
most marine predators swallow their prey head-first, so that it’s preserved tail-forward. Plus, the baby is curled up like a typical
vertebrate embryo. It’s in the fetal position, or as close
as you can get for a reptile whose neck is longer than its body. So whatever’s stopping birds and crocodiles
from giving birth to live young didn’t stop their earliest relatives. Maybe flight makes it impossible for birds,
since they’d have to carry around those heavy, growing offspring. Or maybe there was some other evolutionary
pressure for archosauromorphs to lay eggs. Scientists don’t know for sure yet, but
this study means they are making some progress. Meanwhile, scientists do know that addiction
is at least partly genetic, and some people are more predisposed to form drug habits. And in a paper published this week, researchers
from the University of British Columbia have genetically engineered mice that can resist
cocaine addiction. Their study involved a group of proteins called
cadherins, which help your cells stick together. Cadherin also helps with the formation and
stability of synapses, the gaps between your nerve cells, which your brain uses to do everything
from sending messages through your body to storing memories. Addiction generally involves intense memories. Cocaine molecules, for example, cause a buildup
of extra dopamine, a neurotransmitter associated with feel-good reward systems in the brain. So cocaine addiction changes synapses in that
reward system, to build memories of those euphoric highs, which can make people change
their behavior and keep seeking out that feeling. In this study, researchers genetically engineered
mice to produce extra cadherin, which they predicted would mean more stable synapses,
stronger memories, and more tendency towards addiction. But what they found was the opposite: mice
that were producing more cadherin showed less tendency toward cocaine addiction. Their experiments involved a well-established
method called conditioned place preference, where a box is divided into rooms that are
different enough that mice can tell them apart. The walls of each room can be decorated differently,
the floors can have different textures, there might be different smells, and – in this
case – one of them was associated with a dose of cocaine. In this experiment, the mice were placed in
a room with plain walls while they were high on cocaine, and the other room had stripey
walls. After a couple days of this, the mice were
put in the box without any drug and allowed to wander. The normal mice spent more time in the plain-walled
room, possibly because their reward systems had been tricked into remembering that this
was an awesome place to be. Not that cocaine is awesome. But the mice with extra cadherin spent the
time in both rooms. And the researchers took this to mean the
genetically-engineered mice weren’t forming strong memories related to addiction. It’s possible that, instead of helping create
or strengthen synapses with related memories to cocaine, the extra cadherin prevented
existing synapses from being changed. Now, the researchers caution that this finding
isn’t very ready to apply to humans yet. Our synapses need to get stronger and weaker,
or reform completely for our memories to work properly, so flooding a human brain with extra
cadherins isn’t something we would want to do. What it does help with is understanding which
genes might play a part in addiction. That can help scientists identify people who
might be more predisposed to addiction, or others who might be more resilient, which
could eventually help us develop biochemical treatments. Thanks for watching this episode of SciShow
News, and thank you especially to all of our patrons on Patreon who make this show possible. If you want to support us, go to patreon.com/scishow. And for more videos like this, just go to
youtube.com/scishow and subscribe!


  1. Can you guys do a video on what exactly a virus is? Are they living organisms? How does a virus even come into existence?

  2. the difference between physical and psychological addiction is huge. some people just happen to not form psychological addictions easily… aka people that can quit their d.o.c and once off of it wont have to go to meetings and work on it really hard to stay clean.
    some people are the opposite and are hugely at risk addiction running through every part of their lives

  3. How do you know the genetically modified mice with increased cadherin expression aren't simply moving around more to "actively seek" out a cocaine high, hence spend more time restlessly moving, and so go into striped room more than the control group?

  4. All dinosaurs are archosauromorphs, they're all archosaurs. All dinosaurs are more closely related to birds than either birds or dinosaurs are to crocodiles. Why say most dinosaurs?

  5. What tells us the genetically enginered mice weren't just unable to form new synapses which means that they weren't able to form new memories?
    I mean, Hank himself said that this might cause problems with memorizing, so the mice could just have forgot about the rooms or rather never have saved them in their brain.

  6. There are some species of fish that are ovoviviparous (retain fertilized eggs internally and give live birth). Marsupials are ovoviviparous mammals. And, in the other direction, monotremes are oviparous (egg-laying) mammals (the egg resembling that of reptiles, not of birds). So finding evidence of an ovoviviparous reptile isn't a major shock, just a mild surprise (if that). It was always a possibility, just one we hadn't found any evidence of until now.

  7. I'd be interested to see how these mice would react to mazes, and how their learning ability might be affected. Has their neuroplasticity been lowered too much to learn? I would also be interested in how they might react to repeated exposures of cocaine. Would multiple exposures be enough to cement the memory of cocaine in their synapses, and make them even more addicted, or would there still be no effect?

  8. Was there a crossover control? Did they redo the experiment after a grace period, but getting them high in the stripy room? I can imagine that having a different neurochemistry, may influence the amount of time a subject can stand the relative stimulus deprivation of a clear room, before seeking out a short visual stimulus in a striped room. And vice versa, it could influence how long it takes for the stripes to make you feel icky.

    But the method is well established, so I'm probably not the first to make this remark.

  9. the first one just makes me think it died while laying an egg… that hatched in it… and died.. but i don't know how egg babies of that thing work, nor how any thing on that thing works.

  10. When will you touch on more important topics? For example the high consumption rates, inefficiency of our corrupt policies and environmental degradation? What about mentioning first how stupid to have a political and a monetary system? And when will you inform people about the resource based economy, which is all about science and sustainability? If you really cared about science, and sincere, you would do that. You are full of lullabies, but aware people will not sleep.

  11. 1:45 – You are looking at this "problem" as a hyper-selectionist. Perhaps there is no reason why birds lay eggs beside that is what they inherited and there is not selection against it.

  12. I fear that if this is practiced in the Medical field, cadherin will influence the brain's learning and cognitive development as Dopamine is quite complex when it comes to our memory. With operant conditioning put into considered, this may possibly lead to dysfunctions with motivation and people are inclined to desire less and only be motivated intrinsically. Hopefully they are able to get everything situated with Dopamine since Substance Abuse Disorders are quite devastating in terms of one's health.

  13. This applies to maybe 5% of the target population–so, still good to work on, but it won't help 95% of addicts everywhere.

  14. My mom should be so proud of me because I’m addicted to this game, and not drugs
    iOS: ——— https://itunes.apple.com/us/app/swing-rush/id1030283080??ls=1&mt=8
    Android: —- https://play.google.com/store/apps/details?id=fourtee.wheeldashdash

  15. The ones that stay in the room, were thinking (there's cocaine here) The ones that switch were like ( where's my coke, not here I'll check over the other room, not here either, let's go back to the other room, there's got to be here) If they had more rooms it would be looking for it in all of them. So it wasn't the opposite. One of them was lazy, and the other one was addicted.

  16. I thought addiction was a personality trait? I don't understand how or why addiction exists.. I must have the resilience gene? How do you help someone who doesn't carry that gene??

  17. lol, the scientists running the experiment. " um yes we need some cocaine to um, see if we can make rats not get addicted to it." like is there some scientific industrial cocaine lab for all these drug addiction tests.

  18. Its the year 2017, we havent yet even sound science for evolution bringing about speciation but many evidences to show otherwise. Why are people of "science" so to speak still speaking as if its a given evolution brings about speciation and not just natural selection?

  19. Evolution is still an unproven theory. All animals, warm-blooded or cold-blooded, were directly created as exactly as they are today. Love your site but for such intelligence people, I'm surprised you still believe in this theory.

  20. addiction is a knowledge lacking physiological condition …… and yes genetics may play a role but just because you fell something more intensely or differently …..

  21. We have tons of free help on our website to break a cocaine habit http://birminghamcocaineaddiction.co.uk/blog/

  22. I’m 22 and come from a place where EVERYONE does cocain even my father, I would like to try it but I’m way to afraid , I smoke weed but I take a green out most of the time , if coke feels like going green I’ll stay away lol what does it feel like

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