April 28, 2010
Fewer Dopamine Receptors In Drug Addict Brains
Fewer dopamine receptors in drug addict brains probably means they experience less from the same sources of stimulus.
To get a real-time sense of dopamine activity, Joanna Fowler and her colleague Gene-Jack Wang at Brookhaven, along with Nora Volkow, Director of the National Institute on Drug Abuse, combined positron emission tomography (PET), a medical imaging technology useful for identifying brain diseases, with special radioactive tracers that bind to dopamine receptors. The PET scan highlights the movement of the tracers in the brain, and can be used to reconstruct real-time 3D images of the dopamine system in action.
The scientists tested this procedure on several drug-addicted volunteers as well as age-matched healthy control subjects and found that people with addictions in general have 15-20 percent fewer dopamine receptors than normal and thus cannot bind to a lot of the dopamine released in response to the drugs or natural reinforcers like food.
A treatment that boosts dopamine receptor count would probably make it easier to kick drugs.
Addicts probably do not experience as much pleasure.
"These addicted individuals all had a blunted dopamine response," noted Fowler, a senior scientist in Brookhaven's medical department. "This reinforces the idea that drug addicts experience diminished feelings of pleasure, which drives their continual drug use."
Fowler added that the study looked at multiple recreational drugs and found similar results. "So, while various drugs operate by unique mechanisms, they all share a commonality in that the dopamine receptors in the brains of addicted individuals show an under-stimulated reward system."
How fast do dopamine receptor levels rise after an addict stops using? My guess is that the rate of dopamine receptor recovery is inversely correlated with relapse back into drug use.
This report has important cultural implications as well. So then drug addict "Towelie" has fewer dopamine receptors in his towel brain? Great South Park episode btw. Also, what about Tiger Woods' sex addiction? Does the guy suffer from low dopamine receptor levels? If so, how can he be condemned for medical self treatment?
It's well known that pleasure is diminished among the abusers of dopaminergic drugs, although they can rebound within a few months of abstinence (the numbers I've heard are 3-6 months, although it's an asymptotic curve, where 80% of the rebound may happen in the first three months, another 10% in the next three months, and the last 10% in the next six months, for example). All of this is just the physiological manifestation of tolerance. Dopamine receptor density is reduced in response to high concentrations of dopamine as the system tries to recalibrate to baseline conditions.
Boosting dopamine receptors sounds like a plausibly effective adjunct therapy to the standard practice of abstinence and psychotherapy.
Do users of anti-depressants that are dopaminergic (Wellbutrin, etc.) see the same effect, as well? Wellbutrin's not known to be addictive, and even helps people quit smoking (though that's due to its effect on nicotine receptors).
Perhaps people inclined to become drug addicts simply have fewer dopamine receptors to begin with.
I know i should read the WHOLE article before commenting,but I'm a rule-breaker. Based on just a cursory reading of the test written by Randall, I disagree. If addicts felt less pleasure then why do so many drug trip reports written on sites like Erowid and Bluelight speak of the trips in such glowing,almost ecstatic terms? Also,even if therapy is invented to make addicts have normal dopamine functioning,the number of people abusing drugs like cocaine, I predict will not fall by such a large measure. As taking drugs is done for more than just pleasure or escape from nasty reality,but it's a way of life. Just like computer hacking is a way of life for some people,so drug trips are a similar recreational activity. That's my 2 cents anyhow. Thanks for reading it.
But Martin: a few months back on this site I said i was afraid to use dopaminergic drugs to treat my severe depression, as I read they were neurotoxic to the brain (see the photos of holes in the brains of meth users). I was told that this was sensationalist science,and the rats fed the dopamingergic drugs were given massive amouts of drugs. This was similar to the faulty report on ecstasy destroying seratoninergic neurones,where the rats were fed massive amounts of pharmaceuticals, I believe. But now you're saying that dopamingergic drugs like Ritalin, Concerta, Wellbutrin etc, DO diminish pleasure sensations in the brain.
So which version is right and which is wrong?