An Inserm team has succeeded in designing an experimental protocol for studying binge drinking. Until now, researchers have not had access to any realistic models allowing them to explore this phenomenon which involves consuming large quantities of alcohol in a very short space of time.
Consumption of large amounts of alcohol in a short period of time. This is the definition of binge drinking, excessive alcohol consumption, notably observed among young people. This dangerous behavior is associated with an increased risk of excessive alcohol use in adulthood, together with mood disorders. This is why binge drinking prevention strategies need to be developed.
Mickael Naassila, Head of the Research Group on Alcohol and Drug Addiction* (Amiens), is studying issues relating to alcohol addiction. "Several studies on binge drinking in young people are in progress," he explains. "We are focusing on the cerebral and cognitive consequences of this type of practice. We have notably shown that it causes damage to both gray and white matter." Until now, researchers have not had access to a realistic preclinical study model. However, in their latest publication, Mickael Naassila and his team describe a new experimental protocol which is able to reproduce the binge drinking phenomenon in rats.
In humans, situations like "happy hour", where alcohol is sold cheaply for a limited time, often generate this type of behavior. "This is what we have tried to reproduce in animals", explains Mickael Naassila. "We allowed rats access to alcohol for 15-minute periods, hence very short periods. The animals had to activate a lever to receive the doses of alcohol." By conditioning the rats in this way, the researchers reproduced behaviors associated with binge drinking, taking motivational factors into account as the animals had to self-administer the alcohol and make an effort by pressing on a lever 3 times.
Reproducing binge drinking in animals
"We have found a way of conditioning the rats to consume very large quantities of alcohol. The animals show evident signs of alcohol intoxication, with sedation and loss of motor coordination which characterize binge drinking. The animals voluntarily and rapidly consume excessive quantities of alcohol. However, some differences are observed, with moderate binge drinkers (blood alcohol levels of 0.8 g/liter) or more severe binge drinkers (blood alcohol levels of 2.0 g/l). We are able to draw a parallel with our research in humans," explains Mickael Naassila.
Several outcomes have made it possible to validate this study model. Firstly, the animals suffer from locomotion disorders from blood alcohol levels of 0.8 g/l, which corresponds to the proposed intoxication threshold for defining binge drinking in humans. The researchers then observe impairment of decision-making ability in the rats, another characteristic symptom.
WHO defines this behavior based on the consumption of 5 to 6 glasses of alcohol per occasion. Nonetheless, major differences exist between individuals: some consume 10 glasses per hour, others 15, or 20… and also for different reasons, from the desire to celebrate, to drinking as a way of dealing with problems or anxiety, for instance. Binge drinkers therefore constitute very diverse groups. It is essential to have access to an experimental operant model to shed more light on this phenomenon, the associated vulnerability factors, and its neurobiological bases.
Understanding binge drinker diversity for effective prevention
Mickael Naassila's team aims to evidence the individual determinants which make some people more susceptible than others to such practices. Studies are already under way in this animal model, on the differences between males and females, the role of anxiety, social interactions, impulsiveness, and even environmental factors, which can exacerbate binge drinking.
"A targeted strategy is essential to achieving effective prevention in humans. Hence the significance of defining subgroups," Mickael Naassila continues. Working with an animal model is significant because the environmental parameters are fully controlled, and individuals can be compared before and after introduction to binge drinking. This approach will ultimately shed light on the individual factors at play in this behavior, and will enable different consumer groups to be defined, in humans, according to their characteristics.
*Inserm Unit 1247/Picardie Jules Verne University, Research Group on Alcohol and Drug Addiction, Amiens
J. Jeanblanc et al., Face validity of a pre-clinical model of operant binge drinking: just a question of speed. Addict Biol, online edition dated June 4, 2018