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Nachrichten, Termine, Experten
Beer at the end of the working day, red wine in a romantic atmosphere and the digestif with 40% alcohol content after a good meal. For the majority of the population, alcohol is part of everyday life and many see it as a small, everyday reward. Most people know when they have had enough or can judge very well when no more alcohol should be consumed.
Yet about five percent of the population – in Germany this translates to about four million people – develops a dependency after increased alcohol consumption. These people lose control – over themselves, over their drinking, and over alcohol, something that finally leads to pathological alcohol addiction.
How does this loss of control come about? To date, very little is known about this, but it can be said for sure that the root of this loss is found in the prefrontal cortex. As executive center, this area influences most of everyday life behavior and this includes control over attention as well as of motivations and emotions. At ZI's Institute of Psychopharmacology (scientific director: Professor Rainer Spanagel) this subject has been researched successfully. Simone Pfarr, PhD candidate in the molecular psychopharmacology work group led by Adjunct Professor Wolfgang Sommer, could identify – after conducting many experiments in the rat prefrontal cortex – a small group of special nerve cells, the "awareness cells", whose task it is to interrupt certain unconscious habits. Together with other ZI scientists, she was able to deactivate precisely these neurons in living animals. When the rats were in an environment in which they were accustomed to receive alcohol, then a stronger urge to drink alcohol was triggered when the "awareness cells" had been inactivated.
The experiment makes clear that when memory content is recalled – in this case, when the rat recalls the connection of specific stimuli (smell, light, surroundings) with alcohol – certain neurons are activated and some of them have the task of actively suppressing a stimulus response. This makes it possible to perceive a situation consciously at first and possibly to evaluate it before a certain action is performed, for example the unmindful or habitual drinking of alcohol.
To accomplish this complex task, certain nerve cells join together to form small groups, so-called "functional ensembles". Especially in higher brain functions, such as cognition or behavior control, this special form of work organization in the brain plays an important role. In order to understand these structures and their function better, a new special research area (SFB 1134) was created at the University of Heidelberg in which Adjunct Professor Sommer participated with a project.
With the latest experiments published in the scientific publication Journal of Neuroscience, his work group could now prove that there is also a "functional ensemble" for controlling alcohol-related impulsiveness. This discovery has now allowed researchers to purposefully research the control process and with it, the cause for the loss of control as well. One important initial result is the localization of the found ensemble described above. The specific area in the prefrontal cortex is named Area 25 by the neuroscientists. This structure is regarded as coordinator of a network extending across many brain structures. It plays an important role especially in the development of depressions.
In an earlier study, Sommer's team had already shown that neurons in Area 25 react especially sensitively to repeated heavy alcohol consumption. Long-term damage in this region is seen not only in rats, but also in alcoholics. Together with the results described above, an initial concept is obtained that explains why a functional failure in this brain region interferes with fundamental mechanisms of mindfulness and therefore reinforces the danger of a relapse among alcoholics. These findings additionally stress the significance of the prefrontal cortex in the development of dependency-related conditions. In the future, an improved understanding of the functions of the prefrontal cortex could result in better therapies and urgently needed diagnostic markers for the early recognition and prognosis of alcohol addiction.
Contact:
Adjunct Professor Dr. Wolfgang H. Sommer
Institute of Psychopharmacology
Director of the Molecular Psychopharmacology Work Group
Tel.: 0621 1703 6286, -6259
E-mail: wolfgang.sommer@zi-mannheim.de
Publications:
Pfarr S, Meinhardt MW, Klee ML, Hansson AC, Vengeliene V, Schönig K, Bartsch D, Hope BT, Spanagel R, Sommer WH. Losing Control: Excessive Alcohol Seeking after Selective Inactivation of Cue-Responsive Neurons in the Infralimbic Cortex. J Neurosci. 2015 Jul 29;35(30):10750-61.
Meinhardt MW, Hansson AC, Perreau-Lenz S, Bauder-Wenz C, Stählin O, Heilig M, Harper C, Drescher KU, Spanagel R, Sommer WH. Rescue of infralimbic mGluR2 deficit restores control over drug-seeking behavior in alcohol dependence. J Neurosci. 2013 Feb 13;33(7):2794-806.
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