Monday, 30 April 2012

The Genetic Explanation for Addiction

Professor Derek Denton of the Baker Research Institute Melbourne sought to discover the reason for humanity’s many addictions. The answer came from an instinctive trait that has been developed over hundreds of millions of years – sodium appetite.
These ‘instincts’ are “genetically programmed systems in the brain” (Denton), which if found to be advantageous to survival were passed on from one generation to the next.
The natural instinct of sodium appetite coincides with the instinct of thirst, and thus this ‘genetic program’ has been harboured for over hundreds of millions of years.
This natural need for equilibrium in salt, water and energy intake was closely related to the hypothalamus, an area of the brain responsible for much of our instinctive behaviour.
Professor Denton identified the sodium appetite within even the kangaroo. When presented a whole range of solutions containing sodium, potassium, calcium etc. The kangaroos would always prefer the sodium over anything else. This is because for any animal the quickest way of restoring balance in salt, water and energy intake was through a salty solution – particularly for wild animals where they can quickly restore equilibrium and reduce their vulnerability to potential predators. 
He and his team thus sought to stimulate a sodium appetite in mice and observe the genetic patterns within the brain. By giving the animals ACTH (adrenocorticotropic hormone) the team found that the genes activated by sodium deficiency were similar to those of cocaine, opium and heroin addiction in humans. These substances had in fact found a way of connecting themselves to one of humanity’s oldest instincts, the sodium appetite, something that has been “evolved over at least 180 million years”.
Now, one can imagine the possibilities of such a discovery. With knowledge that many of humanity’s addictions are linked to the age-old appetite for sodium, the inhibition of this instinct may possibly become a form of treatment for addiction.
The problem with any addictive substance or behaviour is the satisfaction and pleasure us humans receive from it. This is attributed with Dopamine, a chemical in the brain that programs a form of reward based learning for instinctive behaviour.  Highly addictive drugs such as cocaine or alcohol use Dopamine as a means of deriving satisfaction from their use. This is part of the reason why it is so difficult to discontinue the use of these drugs – these people are actually being tricked into drawing upon an ancient instinct.
Such findings are directly related to the obesity pandemic of modern society. Many of “obesity-generating” foods are packed with sodium, playing upon an ancient instinct.
One of the most prolific substances on a university campus, alcohol and even one of the most basic survival instincts for any species, sex – are all stimulants for Dopamine.
If these urges could be turned off through a form of dopamine inhibition one could imagine the potential for a humanity unhindered by addiction.

Wolfgang B. Liedtke, Michael J. Mckinley, Lesley L. Walker, Hao Zhang, Andreas R. Pfenning, John Drago, Sarah J. Hochendoner, Donald L. Hilton, Andrew J. Lawrence, Derek A. Denton. Relation of addiction genes to hypothalamic gene changes subserving genesis and gratification of a classic instinct, sodium appetite. Proceedings of the National Academy of Sciences, 2011; DOI: 10.1073/pnas.1109199108
The Science Show, presented by Robyn Williams
Professor Derek Denton, Consulting Scientists, Baker Research Institute, Melbourne

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