You all may recall that I posted recently about cocaine escalation in rats. Drugmonkey has also been posting some interesting stuff about addiction and…EXERCISE. And of course, Sci can’t see that and leave it alone. So I’m going back to a paper that really galvanized the idea of exercise in treating addiction.
Sci deeply considered titling this post “Becoming Lindsay Lohan: Cocaine Escalation in Rats”. But then I thought…nah…too much. 🙂
Anyway, a post over at Drugmonkey yesterday got Sci to thinking about drug self-administration in rats, and more particularly, HOW we use it to model cocaine addiction in humans. Because, like other models, drug self-administration in rats has evolved over time, and will probably evolve a lot more as we come up with better ways to model how humans proceed from drug taking that is once in a while and normal, to the kind of drug taking that takes over a life. We call this escalation, and many scientists believe that there is something very important in the switch between the recreational drug taking, and that escalation toward uncontrolled drug taking that is a hallmark of drug addiction.
And what better way to talk about this, than to go to the paper that, in many ways, changed the drug self-administration world?
But first, let’s have a little overview on drug self-administration in rats (or mice, or monkeys, you get the idea).
Sci had a chance to blog an interesting paper on the value of cocaine in rats (as compared to nice stuff like sugar), and someone pointed out to her that the authors had done a follow up! I think what they found in this followup is really rather exciting and has some very interesting implications for the field of cocaine abuse (at least, I think so).
So here we go. Cocaine vs Saccharin: WWE edition.
Sci would like to start this whole thing off on the right foot, and introduce you all (if you’re new to Scientopia and to Neurotic Physiology) by reposting one of the best posts Sci ever wrote. Unfortunately it was also about the 3rd or 4th blog post that I ever wrote as well. I guess this means I’ve only gone downhill since. 🙂 But that’s ok, enjoy Sci at her height! Here’s Uber Coca, on Freud’s experiences with cocaine.
Let it be known that Sci, like many a young, bright-eyed little scientist, tries to keep up on her reading. TRIES is the operative word, but every week Sci gets the Tables of Contents for all the major journals in her field (and all the major ones in her subdisciple) emailed straight to her for her perusal. She scans the title lists, searching for things that are cool in her field, cool to blog, or that might indicate a scoopage of her work (hey, it happens).
And it was in one of these perusals that I came across this article. And this article is on a subject that needs to be blogged. But this article also says a lot about the “selling” of a scientific paper to a high-ranking journal. Biological Psychiatry, the journal in which this paper was published, has a pretty decent impact factor (8.67), and in Sci’s field, is considered to be a pretty hot publication venue.
But before I go into that, let’s take a look at this paper:
Steiner et al. “Fluoxetine potentiates methylphenidate-induced gene regulation in addiction-related brain regions: Concerns for use of cognitive enhancers?” Biological Psychiatry, 2010.
Sci would like to start by noting that doing an image search for “cognitive enhancer” yields some surprisingly boring results. I was really hoping for something like this:
As you might have noticed, Sci is really interested lately in the concept of food reward systems, in particular the issues associated with the effects of binge eating on reward systems in the brain, and the issue of “food addiction”.
And Sci is not the only one who is interested. Lots of other people in the scientific world (not to mention people outside the scientific world) are interested as well. And in the same issue of Nature Neuroscience that published the paper that Sci covered on dopamine and obesity in rats, David Epstein and Yavin Shaham wrote a commentary on the very same article. Yavin Shaham (the last author and thus the big kahuna) is a big guy in the dopamine and addiction world, and is an important researcher at the National Institute on Drug Abuse.
And these guys have some good points.
Points that Sci (figuring others probably don’t have easy access to Nature Neuroscience) wants to share with you.
Here we go.
Epstein and Shaham. “Cheesecake-eating rats and the question of food addiction” Nature Neuroscience, 2010
Sci would like to note that today’s entry is being written on the adorably tiny screen of her netbook, which is named Ruby. Everyone say hi to Ruby!
Unfortunately, this is because her wireless on her normal computer suddenly decided that it was too good for her modem. Perhaps it’s an April Fool’s Day joke. This is not a good time for this to happen, but of course the not good times ARE the times when this happens, as we all know. And so, until that gets fixed, we are stuck on the netbook, which may mean increased typos and various other things that happen when Sci’s hands are confined to a 10″ space.
A few days ago Sci looked at a recent study which has come out on dopamine and obesity, which showed changes in reward-related behaviors and changes in the dopamine D2 receptor after rats got really fat. This paper (which apparently some people decided to interpret as “food is just like heroin”, which is just silly) was based on the hypothesis that severe chronic overeating results in some changes in the brain which are similar to those seen in drug addiction.
Sci hasn’t really looked into this before, but this really began to interest her. She decided to dig in a little, and take a look at some of the clinical literature, in particular some of the human stuff.
And so here we go.
Wang et al. “Brain dopamine and obesity” The Lancet, 2001.
Sci picked this paper today partially because it was handed to her on a platter by the fantastic Dr. Pal, and partially because today she is SO HUNGRY. She’s had a TON of food already today, and is still entirely ravenous. Maybe it was looking at this paper too long.
As I’m sure most of y’all out there are aware, obesity is a problem in the US. No one is sure whether it’s due to increased portion size, increased availability, decreased physical activity, changes in gut bacteria, issues with our behavioral approaches to food, or all of the above. But scientists have been working for a while not only to look at the effects of overeating and obesity, but also to look at what CAUSES these things in the brain and body. And today we present a paper on an interesting piece of this puzzle, one that Sci has had a good deal of interest in: the idea of overeating as an addiction-like phenomenon.
Johnson and Kenney. “Dopamine D2 receptors in addiction-like reward dysfunction and compulsive eating in obese rats.” Nature Neuroscience, 2010.
(If we’re going to talking about food and addiction, behold Sci’s drug of choice)
You people. You people and your REQUESTS. Requests to do things like blog more about opponent-process theory. Well. Sci hears you. She obeys. At least this time. And for all your drug addiction experts out there asking me to read Koob, I can assure you that I have read a LOT of Koob in my time. For those of you not necessarily familiar with the drug abuse lit, George Koob is considered one of the greatest minds in current drug abuse research, and has done a lot to conform the motivationally-focused opponent-process theory to the model of drug addiction that exists today. Guy even has a wikipedia entry! That’s how you know you’ve hit the big time.
Perhaps I should put a special category up for “things I like to blog about”. Or maybe just ‘basics’.
Sci’s been a little out of her bloggin’ groove lately, feelin’ her stuff is not up to snuff. But with THIS, Sci will get her groove back. And she will get it back with pictures. Pictures that are drawn in powerpoint so they don’t make your eyes bleed. I care.
So what is the opponent-process theory? The opponent-process theory (hereafter called the OP Theory) is one of the current theories we are using to understand addiction. Because, to be honest, we don’t really understand it. Oh sure, we know about initial rewarding effects, we know about withdrawal, we know about tolerance. But do we really KNOW what it is that makes people walk away from their families and homes and jobs and sell themselves for their next hit? A next hit that, oftentimes, they HATE and need at the same time? …nope. Still working on that.
But one of the theories out there to explain drug addiction and how it may work is the OP Theory.