July 12, 2011
A Salty Appetite Linked to Drug Addiction
(Ivanhoe Newswire) -- A team of scientists has found that addictive drugs may have hijacked the same nerve cells and connections in the brain that serve a powerful, ancient instinct: the appetite for salt.
Their rodent research shows how certain genes are regulated in a part of the brain that controls the equilibrium of salt, water, energy, reproduction and other rhythms "“ the hypothalamus. The scientists found that the gene patterns activated by stimulating an instinctive behavior, salt appetite, were the same groups of genes regulated by cocaine or opiate (such as heroin) addiction.
"We were surprised and gratified to see that blocking addiction-related pathways could powerfully interfere with sodium appetite," co-lead author Wolfgang Liedtke, M.D., Ph.D., an Assistant Professor of Medicine and Neurobiology at Duke University, was quoted as saying. "Our findings have profound and far-reaching medical implications, and could lead to a new understanding of addictions and the detrimental consequences when obesity-generating foods are overloaded with sodium."
"Though instincts like salt appetite are basically genetic neural programs, they may be substantially changed by learning and cognition," co-lead author Professor Derek Denton, of the University of Melbourne and the Florey Neuroscience Institute, who is renowned for his pioneering work in the field of instinctive behavior, was quoted as saying. "Once the genetic program is operating, experiences that are part of the execution of the program become embodied in the overall patterns of an individual's behavior, and some scientists have theorized that drug addiction may use nerve pathways of instinct. In this study, we have demonstrated that one classic instinct, the hunger for salt, is providing neural organization that subserves addiction to opiates and cocaine."
Deeply embedded pathways of an ancient instinct may explain why addiction treatment with the chief objective of abstinence is so difficult, said Denton.
"The work opens new pathways of experimental approach to addiction," Denton said.
The study was the first to examine gene regulation in the hypothalamus for salt appetite. The team used two techniques to induce the instinctive behavior in mice "“ they withheld salt for a while combined with a diuretic and they also used the stress hormone ACTH to increase salt needs.
In terms of survival advantage of this behavior, fast satisfaction of salt appetite makes sense. Among wild animals, the ability to rapidly compensate for salt need by avidly lapping a salty solution means that depleted animals can drink to gratification and leave quickly, reducing their vulnerability to predators.
SOURCE: Proceedings of the National Academy of Sciences, published online July 11, 2011