Scientists have found that addictive drugs may take over the same nerve cells and connections in the brain that cause one’s chemistry to crave salt in their daily routines in a new study from down under Australia in association with America’s own Duke University. The study is the first of its kind 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. Their rodent research showed how certain genes are regulated in the hypothalamus, which controls the equilibrium of salt, water, energy, reproduction and other rhythms in the body’s chemical balance. They also 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.

Professor Derek Denton, of the University of Melbourne and the Florey Neuroscience Institute explains:

“Though instincts like salt appetite are basically genetic neural programs, they may be substantially changed by learning and cognition. 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. The work opens new pathways of experimental approach to addiction.”

Deeply embedded pathways of an ancient instinct may explain why addiction treatment with the chief objective of abstinence is so difficult, and this might be relevant given the appreciable success of maintenance approaches that don’t involve abstinence, like replacing heroin with methadone and cigarettes with nicotine gum or patches.

Wolfgang Liedtke, M.D., Ph.D., an Assistant Professor of Medicine and Neurobiology at Duke University continues:

“We were surprised and gratified to see that blocking addiction-related pathways could powerfully interfere with sodium appetite. 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.”

Liedtke also said the researchers were surprised that they could detect that genes were “turned on” or “turned off” in salt appetite, these patterns were often substantially reversed within ten minutes of the animals’ drinking salt solution, well before any significant salt could be absorbed from the gut into the bloodstream.

The state of the instinctive need and the sodium-depleted state, “spring-loads” the hypothalamus for the subjective experience of reward which follows when animals gratify the need, or a satisfied feeling. This concept is substantiated by their finding that the local actions of dopamine on a sub-region of the hypothalamus are critical for the animals’ instinctive behavior.

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: The National Academy of Sciences

Written by Sy Kraft