http://www.theage.com.au/articles/2007/03/...2868811095.html

SOME people's brains are predisposed to becoming dependent on mind-altering substances, a study has found.

As well as helping scientists understand and treat addiction, the findings could lead to a simple blood test to identify whether a child has a propensity to become hooked.

Researchers agree that drug addiction and excessive sensation seeking, or impulsiveness, are linked but it has been unclear which comes first — impulsiveness or addiction.

Are the half a million people addicted to class A drugs in England and Wales predisposed to addiction because they are sensation seekers, or does chronic drug use cause the chemical changes in the brain that made them addicts?

Scientists at the University of Cambridge report that some individuals are indeed predisposed to drug addiction by the way their brains are wired. They seem to lack the docking points — receptors — for dopamine, a signalling molecule that plays a major part in what neuroscientists call the "reward pathway" to cause the craving experienced by many smokers and addicts.

The findings, published in Science, may lead to more targeted treatments for addiction and other compulsive behaviour disorders with fewer side effects than current options.

Research in humans shows that addicts have changes in their brain chemistry.

To find out if the changes are related to the drugs or trigger dependence, Dr Jeff Dalley and colleagues at the Behavioural and Clinical Neuroscience Institute studied spontaneously impulsive rats with a type of brain scanner.

The team found the rodents had fewer dopamine receptors of a given type in the brain. When both receptor-poor and normal rats were offered cocaine, the impulsive rodents were more likely to use the drug.

The conclusion of the study, funded by the Medical Research Council and the Wellcome Trust, is that the decrease in dopamine receptors renders an individual vulnerable to addiction and is not a consequence of chronic drug exposure.

These findings, made with colleagues in France and Spain, may have important ramifications for a range of addictive substances, including nicotine and opiates, where high consumption rates have also been linked to a similar reduction in this particular kind of brain receptor.

There is also evidence in people linking this brain receptor to certain personality traits — notably apathy, extraversion, impulsiveness — and earlier work has linked another dopamine related gene, Dat1, to attention deficit/hyper-activity disorder (ADHD).

"Much more needs to be done," Dr Dalley said. "The real point of this study is that it shows that this particular receptor is diminished in number prior to taking to cocaine.

"This is important because much previous evidence in human cocaine addicts has likewise found reductions but it was impossible to know whether these changes pre-date cocaine use or emerge as a consequence of such use. The next step is identifying the gene or genes that cause this diminished supply of brain receptors.

"This may provide important new leads in the search for improved therapies for compulsive brain disorders such as ADHD, drug addiction and pathological gambling."

Professor Colin Blakemore, chief executive of the Medical Research Council, said: "This remarkable research brings us close to answering a crucial question — whether the tendency to addiction is at least partly genetically determined.

"There have been hints of this from previous research but now, for the first time, we have evidence of a clear linkage between an inherited brain chemistry in rats and their tendency to become addicted."

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Interesting. One way to increase the number of dopamine receptors is through nicotine use.

To the researchers,



Now, will people ignore this one too? Maybe we might need about 10,000 more studies before its not ignored.

HAHAHAHA thank you for this post--you made my day

Wait, does this give an insight as to why some people like sports, and others like learning concepts? After all, both do have to do with the reward system, which dopamine and such as mentioned above are tied in with

Heres some food for thought, if you never try drugs you cant be addicted to them. If you dont start smoking - you cant get addicted to smoking.

Regardless of the biological variation in individuals brains which can lead to an increased risk of addiction - you still have to actually try the substance to become addicted to it.

So real prevention can occurs by not even starting down that road. People are not born addicted to things, so regardless of biology, its still the individual who decides to use addictive substances or not.

WOOWWW!!! ARE you serious. this is interesting. Please don't say stuff like other people who wishes that behavioral psychological studies like nicotine use will really influence how dopamine receptors are expressed. They can give you insights on how they could be regulated but no more than that . Behavioral effect of drugs are NEVER usually the case in mediating an increase in number of dopamine receptors. how can a neuronal circuit be built from a simple pharamceutical drug or use of nicotine/ addiction and other behaviors to activate and modulate DA genes. electro physiologists and geneticists understand that there are cellular mechanisms that underlie desensitization/ Activation of nACHRs that can contribute to nicotine reward in brain. Some behavioral psychologists call themselves neuroscientists will use their data to sugar coat science with their sayings like in the future we'll find that nicotine/ pharmaceutical (DA) agonists/ antiagonists/ partial agonists to understand other neuropatholgy behaviors in humans like Parkinsons/ ADHD/ Amnesia.

A little advice, behavioral neuroscience studies will keep spinning in full circles for years around what are the specific roles of neurotransmitter systems like DA using more behavioral approaches. which will not give insights to identify accurate signaling mechanisms of DA neuronal targets responsible for specific behaviors.

Have a look at
It is not “either/or�: Activation and desensitization of nicotinic acetylcholine receptors both contribute to behaviors related to nicotine addiction and mood
Progress in Neurobiology, Volume 84, Issue 4, April 2008, Pages 329-342
Marina R. Picciotto, Nii A. Addy, Yann S. Mineur, Darlene H. Brunzell

but science is advancing toward areas in molecular and cellular biology to provide much more evidence to support the role of DA regulation and specific molecular targets that are responsible for behavioral responses such as addiciton and others that are DA- responsive. Understanding modulation of neural circuits that either show addiction is predetermined in new borns or if people simply get addicted to drugs once they get hooked on them. Research in those areas are quite hard than you think. Again you don't expect a simple philosophical reasoning like you have to try the substance first to get addicted. this type of behavior doesn't initiate the behavioral response of addiction but gives only a correlation if DA neuron is readily expressed in addicted individual then smoking can enhance this activity through repetitive use of drug.


Wish them good LuCK!