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Tolerance and withdrawal

The video explores how drugs impact our brain's reward circuit, leading to tolerance and addiction. It explains how prolonged dopamine stimulation from drug use can alter brain chemistry, causing the brain to shut down some receptors, resulting in tolerance. Without the drug, withdrawal symptoms like depression and anxiety can occur. Over time, the brain can adjust to the absence of drugs. Created by Carole Yue.

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  • aqualine ultimate style avatar for user susa5
    Why is it that drugs such as cocaine will cause the brain to release more dopamine than hugs and chocolate? What makes drugs so powerful? I understand that one of the "advantages" of drugs is that there is very little effort required to gain the reward. By that logic, shouldn't easily obtained chocolate or hugs also cause intense addiction?
    (19 votes)
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    • leafers tree style avatar for user Ryan
      Drugs like cocaine are psychoactive, meaning they specifically target dopamine receptors to increase the pleasure-reward system. Chocolate and hugs result in the activation of the pleasure-reward system and thus elicit a neurochemical response of which is secondary "side-effect" if you will. That is a very general explanation.
      (40 votes)
  • piceratops tree style avatar for user Sergio Camba
    At , you said the body will shut down receptors. Is this tolerance formation known? Meaning do we know the chemical pathway or know how permanent this is?

    -love these videos
    (7 votes)
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  • blobby green style avatar for user marbrobella123
    say if you take melatonin at night(to help with sleep) will your body soon become immune to it and the melatonin not affect you as much?
    (4 votes)
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  • leafers tree style avatar for user Faith Marks
    Can tolerance with a substance such as nicotene or caffeine result in taking more as you become more addicted? Such as with nicotine you smoke one pack in a day for long-term users vs. a couple a day for starters?

    Also, what makes a person go from not liking smoking and coffee eg. coughing, (for nicotine), and hating th etaste of coffee (caffeine) to liking it and smoking/drinking it reguarly? Is it because your body gets used to the effects (of nicotine, and taste of coffee) and learns to cope wth them, eventually liking them due to the nicotine or caffeine?

    Any help would be appreciated, thanks!
    (3 votes)
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    • male robot johnny style avatar for user 🅹🅾🅷🅽🅽🆈
      I know this is a late response, but if you don't know the answer yet, here it is:

      For your first question, yes. That is a big part of addiction with drugs. A lot of the dopamine receptors shut down, and this makes you increase your dosage as you go on. A failure to meet this results in withdrawl symptoms.

      Not necessarily "liking" it, but getting used to it. Even if the taste is bad, it is an addicting substance, and without smoking or doing drugs, you get withdrawal symptoms. BTW, some withdrawal symptoms can be stronger than others.
      (1 vote)
  • orange juice squid orange style avatar for user okki
    How are "crash" and "withdrawal" related? Do they mean the same thing in the content of drugs?
    (1 vote)
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    • old spice man green style avatar for user Diego Hernandez
      I think that crash is an unofficial term for when you have had too much of a drug and then you feel the detrimental affects later, like a hangover. But withdrawal is different. Withdrawal is when you stop taking a drug. This can also be detrimental depending on how much of a dependence you have on it.
      (5 votes)
  • stelly orange style avatar for user nanabunny
    What are neurotransmitters? And if the receptors in one's body shut down because of tolerance, would they recover over the time naturally (without using any treatment)?
    (1 vote)
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    • leaf green style avatar for user Shane McGookey
      Neurotransmitters are the chemical messengers in our brains. Neurotransmitters are how our brain communicates messages between neurons, and they are responsible for many of our emotions.

      Between neurons in the brain are areas called "synapses." The synapse is an open area between neurons, where the sending neuron (the one sending the neurotransmitters to communicate a given message) will place the neurotransmitters it's sending. The receiving neuron (the one meant to receive and process the neurotransmitters) has receptors in the synaptic area that will receive the message from the sending neuron and do what it may with it.

      As an example, if an event were to make you happy and this event triggered the production of the neurotransmitter serotonin, then one neuron would send serotonin to the synapse. The receiving neuron would receive that chemical message (the serotonin) through its receptors, thereby stimulating the emotion of happiness and contentment. Any remaining serotonin in the synapse would then be taken back by the sending neuron in a process called "reuptake."

      If you search up "neurotransmitters," you'll find a large list of different chemical messengers responsible for various behaviors, feelings, etc. It's quite fascinating if you have the time.
      (2 votes)
  • duskpin ultimate style avatar for user sophie
    Why does the brain want to balance out dopamine levels? Is there an evolutionary reason that would advise against constant happiness?
    (2 votes)
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  • blobby green style avatar for user Ashlea G
    If the number of dopamine receptors in the post-synaptic cell is reduced, but the amount of NT in the synapse remains the same, would those receptors be saturated? And how would an increase in drug intake/dopamine release increase stimulation?
    (2 votes)
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  • blobby green style avatar for user Kristina Pagano
    What is the difference between withdrawal symptoms and craving symptoms? Isn't withdrawal = craving in substance abuse?
    (1 vote)
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    • leaf grey style avatar for user Abdelrahman
      Withdrawal symptoms typically refer to chemical dependence, i.e. physiologic effects of the drug. As an example, a barbiturate addict who develops seizures when denied the drug. Craving on the other hand refers to psychological dependence. Some people may not experience significant physiological side effects when they stop smoking, however the psychological attachment to the behavior is troubling and hard to resist. Chemical and psychological dependence are not mutually exclusive, and patients may suffer both withdrawal symptoms and craving at the same time.
      (3 votes)
  • blobby green style avatar for user Sally
    This video will not play for me. There is a partially concealed message about restricted access behind the play button. This is for a course. Any hints on how to watch it. Im watching 9 drug related videos in this segment. The first 6 played with a little coaxing. Now this one refuses to budge.
    (1 vote)
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Video transcript

- So, in the previous video, we talked about the reward circuit in the brain at sort of a broad level. And now, what we're gonna talk about is how that works at a lower level, at the neuron level, so that we can discuss issues like tolerance, addiction, and withdrawal. Now, behaviorally, tolerance just means that you get used to a drug so that you need more of it in order to achieve the same effect. So, let's look at how that works inside your brain. So let's take a look at what's happening with the neurons here. So, imagine that this is the axon of one neuron, and the dendrite of another, and then in here is the synapse. All right. So then, we have these neurons. They're coming from the VTA and they're sending dopamine. So imagine that you've just taken some cocaine, so all of this dopamine is flowing, pleasure signals going crazy, you're pretty happy. Okay, so tons of dopamine. And what normally happens here is that the postsynaptic neuron has receptors for certain neuro-transmitters, such as dopamine. It has these little spots for the dopamine to come, and it gets taken up, and it sends the signal on, and that's how you experience the euphoria. It's that stimulation of the neurons along that pathway. Now, in a normal situation, if your stimulus had been, say, a hug or something, then you would still experience this feeling of pleasure, but then your brain chemistry would go back to normal after a second. It would balance itself out. With drugs, long-term stimulation can actually alter your brain chemistry. So what happens when your brain is just constantly over-stimulated with dopamine, it's too much for it, and it tries to balance it out. Believe it or not, you don't always wanna be super-duper happy. At least your brain doesn't. So what happens after a while is it says, "Okay, I need to calm down. "I'm gonna shut down some of these receptors, so that way, "the same amount of drugs won't cause me "to be so over-stimulated. "I won't get as much of a high from the same amount of drugs." And so, when that happens, that is called tolerance, because you have built up a tolerance to the same amount of drugs, and it doesn't have the same effect anymore. Now, with drugs like cocaine in particular, this can cause a problem, because you've started to develop a dependence on it. We usually talk about a combination of emotional dependence-- a feeling like you need the drug-- as well as a physical dependence-- you actually experience negative physical symptoms without it. So once you've built up this tolerance and you still wanna feel that high, you end up taking more cocaine to get the same feeling. And so then, you just have to keep kinda increasing your dosage over time. Okay, so that's what happens if you have just free and steady access to drugs: you just keep increasing your dosage up to a point. On the other hand, you might not always have access to the drug, and if you go through a period of not having it, then that is when you experience withdrawal symptoms. So, remember, now your body has gotten accustomed to this very high level of dopamine, and it's gotten accustomed maybe to not producing it on its own, but relying on the drug. Once you start taking cocaine, I mean, things like chocolate and hugs won't make you quite as happy as the cocaine does. You end up seeking out this cocaine and the pleasurable sensations it can produce in the place of other types of stimulation. So then, without it, you don't have the same level of dopamine, your body's not producing it on its own, so you tend to feel depressed, you feel highly anxious, and the specific symptoms will vary by type of drug. Sometimes you'll sweat, have headaches. Generally, anxiety and depression are pretty common, and when those are extreme enough, you'll really do whatever it takes to make yourself feel happy again. The thing is, though, you're not even going for the euphoria anymore, you're going for normal. Once you've built up this tolerance, you need the drug to feel normal again, not even euphoric. And this is usually a sign that you are addicted to the drug, which means that you feel a need to keep taking it. The good news is that even though withdrawal is miserable, just like your brain can get used to the presence of drugs, it can used to the absence of drugs again. So, with some time and effort, even if the drugs have caused some irreparable damage to other parts of your brain, you can get your reward system back to functioning at a more normal level.