Scientists experimenting with genetically-modified mice said on Wednesday they had unveiled a molecular pathway that helps explain drug addiction and appetite.
The discovery focuses on the chemical process by which people become substance-dependent, according to the study, published by the British journal Nature.Pleasure-giving drugs such as cocaine and heroine -- as well as food -- work by boosting levels of a messenger chemical called dopamine that stimulates the brain's "reward" centre.
But dopamine itself is only one part of a molecular cascade that leads to dependence.
Researchers led by Jean-Antoine Girault of the Pierre and Marie Curie University in Paris looked at a brain protein called DARPP-32 which helps the dopamine signalling process.
The team found that when lab mice were given a jolt of cocaine, amphetamine or morphine, DARPP-32 built up in part of the brain called the striatum.
They then created mice whose DNA had been modified so that the gene expressing DARPP-32 turned out a slightly altered form of this protein -- a form where just one amino acid building-block had been changed.
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Just as interesting was the discovery that mutant mice trained to use their noses to poke a lever mechanism that delivered a food pellet were far less likely to push for the reward compared with their wild counterparts.
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Finding a pharmaceutical drug that can block the accumulation of DARPP-32 is a promising avenue for tackling addictions as well as certain kinds of mental illness in which dopamine is suspected to play a role.
Knowledge gained from this work could also help fine-tune treatment for Parkinson's disease, which is caused by dopamine depletion, France's National Institute for Health and Medical Research (Inserm) said in a press release.
Source-AFP
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