The Key to Addiction

17. July 2007

It's all about the kick. How does it develop and by what? What goes on in the brain, when you get addicted? There are many models to explain the development of addiction. Seventy years after the discovery of Acetylcholin, scientists found a new role of the carrier substance. Not Dopamin but Acetylcholin makes people addicted.

The core structure of the basal anterior brain, the Nucleus accumbens, plays a central role. It decides how we feel. Univ.-Prof. Dr. Gerald Zerning-Grubinger and Univ.-Prof. Dr. Alois Saria of the department for neurochemistry at the university hospital for psychiatry in Innsbruck probed the biochemical causes of development of addiction more closely. They wanted to know which neurotransmitters in the Nucleus accumbens are responsible if people start taking a fancy to addictive drugs. The results provide a completely new understanding: It's not the neurotransmitter Dopamin but the Acetylcholin which is responsible for people getting addicted.

Acetylcholin booms

Experiments with rats show that the very moment the animals started getting interested in a drug, the learning messenger Acetylcholin is released. “With this our results lead to an essential widening of the dogma that the release of Dopamin in the Nucleus accumbens is the neurochemical one key factor for addiction”, explains Zernig-Grubinger. His team has quantified the attraction of addictives in a simple manner on mice: Dr. Jose Crespo measured the speed a test animal took to run towards a chamber containing intravenous drug-injections with Phentanyl. At the same time an analysis was made of the released neurotransmitters by tandem-mass spectrometry. It separates and identifies molecules physically according to their mass.

Within only five tests the speed of the rats decreased from three minutes to two to three seconds. The quantity of Acetylcholin nearly exploded and increased fourfold. But the Dopamin level stayed the same during the first learning experience. “Animals completely naïve to addiction reacted really heavy” says Zerning-Grubinger. “We also found out that neither a maximum level nor a minimum level influences the flush out rate of the drug or of Dopamin regarding the decision of the test animal taking drugs again. ” Therefore addiction is not like level drinking but connected closely to old memories of drug use. They cause the repeated use of the drug. But not every rat started racing towards the drug during the tests. Obviously those animal developed different mechanisms dealing with addiction.

Important therapeutic consequences

Not only the expectation of an addict awaiting the effect of a substance that makes way for addiction by addiction memory is fatal. “Every person takes own stock of his experience” explains Zerning-Grubinger.

The findings of Innsbruck researchers can bring completely new therapy possibilities for addicts medium-term. They will help to develop medications to use as implemental aids together with psychotherapy. The most exiting vision is a vaccine against addiction. The basic idea sounds simple: targeted intervention should influence the addiction memory. The people in Innsbruck now hope for an intensive co-operation with the Alzheimer research because it has been concentrating on the messenger Acetylcholin for a long time.

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