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meth and the brain

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Richard A. Rawson, Ph.D is an Adjunct Associate Professor in the Department of Psychiatry and Biobehavioral Sciences at the David Geffen School of Medicine, University of California at Los Angeles.

In this audio slideshow, Dr. rawson explains how meth affects the brain's dopamine receptors, causing the intense pleasure associated with a meth rush and yet eventually making it impossible for the user to experiene an pleasure at all.

slide three

One of the questions we often get is, why do people take this drug? And people start taking drugs for a whole variety of reasons. Curiosity. Peer Pressure. In the case of methamphetamine some people take it because they know they can lose weight with it. But after they've taken the first dose for whatever reason, why they continue to use it is pretty common. It's because they like what it does to their brain. They like how it feels.

Methamphetamine effects the centers of the brain that control judgment, control reward, and control memory. The most important one probably are the reward centers of the brain. When, when that part of the brain is stimulated dopamine's released, and you experience that as pleasure. Under normal circumstances those responses occur for naturally occurring rewarding events.

Similarly if you put a rat, a male rate in a box and you give him access to a receptive female, and you allow them to have sex, at the point where they experience orgasm you get a huge release of dopamine. You see an increase of about 200 units. This rush is what feels good and what is experienced is pleasure. And this slide of course illustrates the principle that one orgasm equals two cheeseburgers.

slide seven

Now drugs of abuse release dopamine. Alcohol, for example, produced a release of dopamine from about 100 units to about 200, You get a similar magnitude of an effect with nicotine. Cocaine produces a huge release of dopamine, from 100 units to about 350 units, however the mother of them all is methamphetamine. Methamphetamine you get a release from the base level to about 1250 units. A tremendous increase of dopamine. This produces an extreme peak of euphoria that people describe as something like they've never experienced and they probably never have experienced before because the brain really isn't made to do this. And that's why people will be attracted to it and want to take it over and over and over again. They want to produce that response.

Over time doing this to the brain and having it feel good changes the way the brain works. Part of what we've learned about addiction is that addicts, after they've used drugs, have different brains than they did before they used drugs. The units that are changed are these, the neurons. Dendrite, cell body, axon, terminal. Dopamine has its effect here at the terminal. Dopamine is stored in the nerve terminals in these, in these little sacs called vesicles. Sit there waiting until a nerve impulse comes down from the, the neuron, causes these to move to the cell wall and release their dopamine.

These little dopamine guys get released, they float across the synapse, they attach on the receptor and they cause the downstream neuron to fire. If that goes on in the reward centers of your brain that feels good They sit here for a few microseconds, they're released, and they're taken back in and recycled. That's how the pleasure system is supposed to work. You have this recycling where these mechanisms called reuptake pumps pull them out of the synapse and bring dopamine back in to be reused. When you take cocaine, the only effect cocaine has is to sit on these reuptake pumps and block them. That means that as this cell fires and releases dopamine into the synapse dopamine accumulates because this ting has been deactivated. Dopamine accumulates causing this cell to fire and fire and fire way longer than it's supposed to because the dopamine isn't being pulled out of the synapse. And in fact cocaine will sit here for an hour or two causing this big accumulation of dopamine and this extended feeling of pleasure. Now methamphetamine takes it one step further. Methamphetamine actually will sit here for eight to 12 hours causing this build up of dopamine for a much longer period so you experience this positive feeling for a longer period of time plus methamphetamine is actually taken into the terminal and destroys the nerve terminals.

slide thirteen

Now luckily for meth users they regrow; however the bad news is they take quite sometime and for months meth users are feeling the absence of this reward because the reward center of the brain has essentially been damaged. Other areas of the brain are also effected. This is an MRI of the human brain done here at UCLA and this shows the judgment center of the brain in the prefrontal cortex. This is the brain of a meth user who's about five days sober and this blue area represents a reduction in normal activity, a reduction in blood flow. In essence, this part of the brain is shut off and for meth users who are in early recovery, they really don't have the ability to make good decisions.

You have this sort of worst-case scenario. You have a brain that is not producing reward, you're having a lotta craving because you want to feel better, and you have the part of the brain that controls judgment not working, and so individuals do stupid things that end up with them relapsing and going back to using. It's a wonder any meth users ever get better, but in fact they do.

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posted feb. 14, 2006

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