The brain-addiction connection : Neurons and neurotransmitters

As I’d mentioned in an earlier post, while many people experiment with, or use, drugs at some point in their lives, only a small percentage (between 10%-15%) develop chronic drug abuse and dependence¬†problems. While some of the specifics of what makes one person more likely to move from recreational use to addiction are still being investigated and hotly debated, we do know quite a lot about what happens in the brain when drug are used.

Before I can go into the specifics of the brain-addiction connection…

We need a little background on the way the brain works:

The neuron

The brain is in essence a very complex network of interconnected fibers (neurons) and their maintenance and support structures. The brain contains about 10,000,000,000,000 (10 trillion) of these cells, and they each make many connections.

The left end of the neuron in the picture on the right is called the dendrite; this is the neuron’s main information receiving hub. The long part extending to the right is called an axon, and it ends in axon terminals that eventually connect to other neurons’ dendrites.

This is the basic way in which everything that happens in the brain is communicated, including our thoughts, feelings, movements, and memories!!! Dendrite to axon, to axon terminals, to dendrites, and back to step 1. How this transmission is achieved within the neuron is not necessary for this discussion; let’s just say that you should eat your bananas and make sure you always have some potassium, sodium, and calcium in your body…

How do the neurons talk to one another?

Neurotransmitters

What is important for us is the way these neurons transfer information across the gap between the axon terminals and their connecting dendrites. This is achieved by chemicals called neurotransmitters. There are quite a few of these, but the main ones we’re going to be concerned with are serotonin, adrenaline, GABA, and dopamine as these are some of the major players in drug addiction (especially dopamine).

When a neuron wants to send a signal to its neighbor, it releases packets of a neurotransmitter (most axon terminals release only one specific neurotransmitter), and these are received by specialized receptors at the dendrites of the receiving neuron. If enough neurotransmitter is released and enough receptors are activated, the signal starts again and the cycle continues…

Neurotrasnmitters and drug use

Most abused drugs disrupt some combination of factors within this mechanism to produce both the intended, and unintended, effects they are known for.

Alright, that’s probably enough to absorb for now, more on what specific drugs do to interrupt this process soon!

Question:
How many of you knew about the ways in which drugs affect the brain? Would you mind sharing the things you’ve learned and where you’d learned them?

About addiction: Prescription overdose, legalization, methadone, and the brain.

Here are this week’s must reads posts about addiction. Don’t forget to click the title for our related posts!

From the other allaboutaddiction (.net) Overdose deaths due to prescription medication

From Addiction InboxThe economics of drug legalization

From Addiction TomorrowA great balanced post about methadone

From PhysorgThe neurological consequences of early meth exposure

That’s it for this week. Enjoy!

Marijuana addiction ‚Äď Literature search results on marijuana facts

My recent post on marijuana’s addictive potential received some scathing comments from readers who seem to think that the scientists have already agreed that marijuana addiction (called marijuana dependence in the field) does not exist. So, I’ve compiled this little list of research articles. I’ve made certain to only use articles that have been cited often (in other work), meaning that their content has made an impact. Each of these papers has been cited at least 50 times (except for the very recent last review with about 40). Once again, I find it odd that only marijuana users are so insistent about their drug having no negative aspects whatsoever.

1. Laura Jean Bierut, MD; Stephen H. Dinwiddie, MD; Henri Begleiter, MD; Raymond R. Crowe, MD; Victor Hesselbrock, PhD; John I. Nurnberger, Jr, MD, PhD; Bernice Porjesz, PhD; Marc A. Schuckit, MD; Theodore Reich, MD (1998). Familial Transmission of Substance Dependence: Alcohol, Marijuana, Cocaine, and Habitual Smoking. Archives of General Psychiatry, 55, pp. 982-988.

2. Budney A. J.; Novy P. L.; Hughes J. R (1999). Marijuana withdrawal among adults seeking treatment for marijuana dependence. Addiction, 94, pp. 1311-1322.

3. AJ Budney, ST Higgins, KJ Radonovich, PL Novy (2000). Adding voucher-based incentives to coping skills and motivational enhancement improves outcomes during treatment for marijuana dependence. Journal of Consulting and Clinical Psychology, 68, 1051-1061.

4. William R. True, Andrew C. Heath, Jeffrey F. Scherrer, Hong Xian, Nong Lin, Seth A. Eisen, Michael J. Lyons, Jack Goldberg, Ming T. Tsuang (1999). Interrelationship of genetic and environmental influences on conduct disorder and alcohol and marijuana dependence symptoms. American Journal of Medical Genetics Part B: Neuropsychiatric Genetics, 8, 391-397.

5. Aimee L. McRae, Pharm.D., Alan J. Budney, Ph.D., Kathleen T. Brady, M.D., Ph.D. (2003). Treatment of marijuana dependence: a review of the literature. Journal of Substance Abuse Treatment, 24, 369-376.

Montana Meth

A very powerful ad campaign from Montana about the dangers of meth use (thanks to Mike at addictiontomorrow for exposing me to it). Like most advertising, and indeed most media presentations of drug users, the content is a little too stylized, but the point is pretty clear.

I would like to point out that while there isn’t necessarily any research that shows that a single use of meth can lead to addiction, we do know that even using meth for a short while can have serious long term effects on the way the brain functions. This is especially true when talking about some basic learning mechanisms in the brain that affect our ability to change our behavior (look for a post on this shortly)

Recent online mentions

Our blog has recently been mentioned in a few places on the web including:

Some Chick’s Blog – A great online resource for meth specific information. Last I heard the author was working on a meth Wiki that would allow people to educate themselves about this destructive drug.

and

Addiction Recovery Basics – Bill’s great blog is just full of resources for people struggling with addiction.

I think that all my readers could benefit from looking into these other online sources of information. While we try to educate and expose people to the latest, most relevant research available on addiction, there’s no way we can cover everything there is to know about addiction. It’s good to have such great people working alongside us.

Tip of the day #1

If you think you have a problem with drugs yourself, try telling someone who isn’t involved in your drug use. Telling using buddies often leads to little in the way of solutions, but people a bit removed from the situation may have as easier time offering help.

Neuroscience updates!!!

Hey readers!

We’ve just passed the 6000 visitor mark and our readership is growing steadily. I want to thank everyone who regularly check the site and welcome those of you who are here for the first time.

I’m in DC right now, attending the annual meeting of the Society For Neuroscience (sfn.org). I have been learning about new exciting developments related to addiction for the past 4 days and can’t wait to share them with you.

Watch out for some great new stuff!!!