The brain-addiction connection: Cocaine, dopamine, and more

Okay, so we’ve covered how the brain’s neurons communicate with one another normally; now let’s learn about how drugs mess things up to produce their specific effects. Since the brain-addiction relationship is different for different drugs, we’ll do this one by one, starting with cocaine:

Cocaine

One of the most commonly abused drugs, cocaine interrupts a molecule in the brain that’s responsible for clearing away the dopamine that is released during normal functioning (it’s called DAT). Like I’d said before, neurons talk to each other by releasing these neurotransmitter molecules to transmit impulses from one to another.

Imagine for a second that every time you spoke, the sound of your voice would continue on, reverberating endlessly. By the time each of us would be done uttering our first sentence, the world would be a mess of unintelligible sounds, echoing forever. This wouldn’t make for a very effective way of communicating.

Sound loses energy as it travels through air, eventually having so little energy that it no longer moves enough air to be audible. This keeps each word distinct and meaningful. In the brain, the individual messages between neurons are similarly kept distinct up by a number of processes.

These include dissipation, chemical breakdown, and reuptake.

Let’s learn more about these processes

Dissipation is a process similar to the story with air and sound, as the molecules move around, their concentration gets lower, and they become less likely to activate anything.

Chemical breakdown does is exactly what it sounds like, chemicals breaking the neurotransmitters down so they can no longer activate anything.

Reuptake is a more complicated process of recycling. Instead of letting all those precious chemicals go to waste, the brain recycles them so they can be used again later. Cocaine blocks the molecule that makes this reuptake process (for dopamine) possible. It’s a small molecule that carries the cocaine back into the cell that released it. Cocaine wedges itself in place of the dopamine (see picture below) and therefore deactivates it.

Dopamine Transport Molecule

What does cocaine’s action result in?

The result is that since it can’t be as efficiently cleaned up, dopamine ends up hanging around the brain for longer than it’s supposed to. Because dopamine is one of the brain’s main “pleasure”, or “positive” signaling molecules, users of cocaine feel better than they would otherwise as a result of this extra dopamine.

This doesn’t sound like such a bad thing, does it? Reuptake is a small price to pay for feeling a high that is almost “naturally produced” (some of the brain’s own dopamine hanging around for longer than it should). The problem is, that like in anything else, for every action, there’s a reaction…

What happens when cocaine in taken for a long time?

Faced with increasing amounts of dopamine, the brain starts adjusting in these ways:

  • It starts out by producing and releasing less dopamine, because as far as it’s concerned, the balance has been interrupted.
  • The number of receptors available to bind with dopamine is also reduced.
  • Next, it starts turning up brain systems that are supposed to counteract the actions of dopamine in order to once again, adjust for the increased levels.

Overall, these are some of the reasons for the “come down” or, after effects of a heavy night of cocaine use.

Over time, many of these changes become long lasting, resulting in a whole set of undesirable effects for the user, including withdrawal, mood problems, as well as some serious problems with thinking and control over behavior.

Not to be ignored are the effects that cocaine use, and the good feelings it initially brings along, have on motivation and normal reward functioning and learning in the brain; but we’ll get to that in another lesson…

Question of the day:
Does the above explanation of how cocaine works help you make sense of the effects it has? Could you see how these effects would possibly bring about addictive, rather than recreational, use?