Hormone and neurotransmitter systems disturbed in alcoholics’ brains.
Excessive alcohol-use is the third leading risk factor for disease following tobacco and blood pressure. The most important include peripheral neuropathy, brain damage, alcoholic liver disease, and nutritional and metabolic disorders. Furthermore, excessive alcohol use increases the likelihood of crime, accidents and violence, impulsivity and antisocial behaviour. Due to the physiological, psychiatric and social consequences of alcohol use, treatment and curative intervention are now crucial. Now, a study from researchers at University of Eastern Finland shows that the brain tissue of persons with alcohol dependence exhibits a variety of changes compared to non-alcoholic control persons. The team state that their findings indicate that all alcoholics’ brains share some characteristics, however, some are exclusive to the brain tissue of anxiety-prone type 1 alcoholics or impulsive type 2 alcoholics.
Previous studies show that the global medical community has long sought the mechanisms by which alcohol acts on the brain to modify behaviour. An important finding is the demonstration that alcohol can affect the function of specific neurotransmitters. Studies of neurotransmitters and the receptors to which they bind have provided data on both the structure and the mechanism of action of these molecules as well as clues to their role in behaviour. However, neurotransmitter systems do not function in isolation, therefore, attention has been garnered as to the integration of communication systems in the brain. The current study shows significantly increased levels of steroid hormones in the brains of alcoholics, and could be associated with the pathology of alcoholism.
The current study analysed post-mortem brain tissue from alcoholic persons and non-alcoholic controls. The alcoholic samples were divided into two groups on the basis of Cloninger’s typology, namely, type 1 and type 2 alcoholics. The lab explain that Type 1 alcoholics develop alcohol dependence relatively late in life, and they are prone to anxiety. They go on to add that Type 2 alcoholics develop alcohol dependence at a young age and they are characterised by antisocial behaviour and impulsiveness; the group stress that the reality is far more diverse, and not every alcoholic fits into one of these categories.
Results show that one of the changes shared by all alcoholics were increased levels of dehydroepiandrosterone, a steroid hormone that affects the central nervous system, in the brain. Data findings show that these increased levels explain alcohol tolerance, which develops as a result of long-term use and in which alcohol no longer causes a similar feeling of pleasure as before.
The team observed that all alcoholics showed decreased levels of serotonin transporters in posterior insula and posterior cingulate cortex, brain regions associated with recognition of feelings and social cognitive processes. They state that this finding could be related to social anxiety type behaviour seen in alcohol dependent individuals.
The study also found changes specific to the alcoholic type. Results show that the brain samples of impulsive, type 2 alcoholics had increased levels of AMPA receptors in the anterior cingulate cortex. The researchers state that by modifying the function of synapses between neurons, AMPA receptors play a role in the learning and regulation of, e.g., behavioural models; this can be associated with the impulsive nature of type 2 alcoholics. In type 1 alcoholics, however, changes were seen in the endocannabinoid system, which modulates stress responses, among other things. With data showing that docosahexaenoylethanolamide levels were increased in the amygdala, possibly associated with the anxiety prone nature of type 1 alcoholics.
The team surmise that their findings enhance the understanding of changes in the brain that make people prone to alcoholism and that are caused by long-term use. For the future, the researchers state that this information is useful for developing new drug therapies for alcoholism, and for targeting existing treatments at patients who will benefit the most.
Source: University of Eastern Finland