Brain “lights up” in response to cocaine or opium

Australian and U.S. scientists have proved that the same area of the brain that is activated when the body craves salt ''lights up'' in response to cocaine or opium, suggesting addictive drugs have hijacked a pathway of the brain used for instinctive behavior.

The findings may provide new understanding on treating addiction, Australia's Sydney Morning Herald reports.

Australian Professor Derek Denton said the findings, published in the journal Proceedings of the National Academy of Sciences yesterday, proved a connection between drug addiction and instinct. Until now, the connection existed only in theory, SMH reports.

Researchers deprived mice of salt by feeding them a low-salt diet and diuretics. Three days later, with the help of Wolfgang Liedtke from Duke University, an area at the base of the brain called the hypothalamus was analyzed for genetic patterns.

''What was surprising was when the data in the genetic pattern was examined, it was clear that the genes that the salt appetite had activated were the same pattern of genes that were altered in addiction to cocaine or to opium,''  Denton, of Melbourne's Howard Florey Institute, said.

A separate group of mice were denied salt over the same period. But unlike the first group, they were allowed ''their fix'' of saline solution. Analysis of their brains after drinking the salt showed a difference in the genetic expression in that part of the brain.

Denton, a world authority on salt metabolism, said while cocaine and opium addiction had evolved in the last two to three thousand years, salt was so basic to survival that it has developed over a hundred million years.

The body needs salt for circulation of blood and tissue fluids, for nervous, glandular and muscle function and also for reproduction.

''This suggests that the addictive drugs have hijacked, if you like, the neural pathways and mechanisms which subserve sodium appetite and the gratification of the sodium appetite,'' Denton said.

SMH reports:

The other key finding was that once saline solution was ingested, the brain believed it had received its fix well before it was physically possible.

The ''repair'' scientists observed in the brain occurred well before the salt could have left the gut, entered the bloodstream and got to the brain to reverse the changes that had created the salt craving.

''It is an evolutionary mechanism of high survival value because when an animal is depleted of water or salt it can drink what it needs in five to 10 minutes and get out which makes it less susceptible to predators.''

The U.S. team also included researchers from the University of Texas.