How does nicotine affect the brain

Long-term effects of cigarette smoking in the brain noted

17.01.2013

A group of researchers from Bern and Zurich examined the effects of tobacco consumption on the human brain and was able to show that the effects of nicotine-nicotine
There are several reasons that the addiction-inducing substance in cigarettes is nicotine:
* Nicotine penetrates the central nervous system (CNS) and is psychoactive.
* The physiological effects of smoking and injected nicotine are identical.
* Nicotine works as a "positive amplifier". Humans (and animals too) add nicotine to themselves in experiments.
* It is easier to get rid of the addictive substance (tobacco abstinence) if nicotine is administered (substituted, i.e. replaced) with medication.
* Smokers tend to adapt their smoking behavior to the different nicotine contents of tobacco products
are stronger than previously assumed and last longer. The findings can potentially help in the development of new drugs.

Smoking is a widespread disease of increasing importance worldwide. Five million people die each year as a result of tobacco use, and it is estimated that the number will rise to ten million by 2030. The addiction to nicotine is often severe: up to 90 percent of smokers find it very difficult or difficult to give up nicotine. Nicotine has both a stimulating and calming effect in the brain and can improve the ability to concentrate in the short term. Repeated nicotine consumption leads to the development of tolerance. This means that the positive effects are weaker and not using nicotine often leads to withdrawal symptoms such as restlessness, irritability, anxiety, listlessness, headaches, sleep problems, difficulty concentrating, feeling hungry and weight gain.

Three quarters of smokers try to quit, but few succeed. Despite the enormous importance of smoking for individuals as well as for society, it has not yet been possible to understand the long-term effects of nicotine consumption on the brain. Researchers from the University of Bern, ETH Zurich and the University of Zurich have now been able to demonstrate in a study that these consequences are dramatic and long-lasting (see PNAS online advance publication on December 17, 2012).

The development of nicotine addiction is a kind of learning process. The brain messenger substance glutamate plays a central role in this. "It is known from animal studies that glutamate is also important in the development of addiction, which is also a kind of learning process - especially in the case of nicotine and cocaine addiction," explains Gregor Hasler, professor and chief physician at the University Psychiatric Services ( UPD) Bern.

That is why the researchers examined the glutamate system in smokers, ex-smokers and non-smokers. Using the newly developed method of positron emission tomography, an important protein of the glutamate system was measured: the metabolically active (metabotropic) glutamate receptor 5 (mGluR5).

The study found that the amount of this protein in the brain of smokers was reduced by an average of 20 percent, and by up to 30 percent in individual brain regions such as the lower frontal lobe and basal ganglia. Ex-smokers, who were abstinent for an average of 25 weeks, also showed a reduction in this protein of 10 to 20 percent.

"This change in the glutamate system in smokers is far greater in scope and distribution than previously assumed," explains Gregor Hasler. It is particularly unexpected that the recovery of the glutamate system apparently takes a very long time. "It is likely that this very slow normalization contributes to the very high relapse rate among ex-smokers."

According to Gregor Hasler, it has not yet been clarified to what extent the ongoing changes in the glutamate system affect learning processes in general - and whether the reduction in the mGluR5 protein is responsible for an increased risk of anxiety disorders in smokers and obesity in ex-smokers. "With regard to the development of drugs that act on the mGluR5 protein, it should be taken into account that the effect on smokers and ex-smokers could differ significantly from the effect on non-smokers," says Hasler. "These drugs may also have the potential to reduce the risk of relapse, withdrawal symptoms, and other psychological consequences of nicotine use."

Source: University of Bern