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Paris - French scientists said on Monday they had found the first biological evidence to back claims that smoking destroys brain cells and impedes the production of new ones.
A team led by Pier-Vincenzo Piazza and Djoher Nora Abrous at the National Institute for Health and Medical Research allowed three groups of rats to administer themselves intravenous jolts of nicotine while a fourth was allowed no nicotine.
The nicotine doses were either low, medium or high.
In all three of the nicotine-taking groups, the rats suffered a major fall in production of PSA-NCAM, a protein which plays a vital role in the "plasticity" of the brain - something that is related to the ability to learn and memorise.
Rodents which took the medium and higher doses suffered a 50 percent higher loss in the production of new brain cells than those in the non-nicotine group, as well as a significantly higher rate of brain-cell deaths.
"These results raise an important additional concern for the health consequences of nicotine abuse and open new insight on the possible neural mechanisms of tobacco addiction," the scientists report in May's issue of a specialist US publication, The Journal of Neuroscience.
The rats were allowed to absorb the nicotine for one hour a day for 42 days before they were killed and their brains dissected.
The authors say their findings counter headline-making studies published in the 1990s that suggested smoking could boost cognitive performance.
These studies even contended that nicotine could help prevent the onset of Alzheimer's disease because this chemical boosted neurotransmitters, which get damaged by dementia. - Sapa-AFP