The effect of age of onset on alcohol consumption and loss of control over alcohol use.

Abstract

Background: Alcohol use disorder (AUD) is a worldwide problem affecting 4,1% of the population aged 15 or older. AUD is characterized by several symptoms amongst which are large alcohol consumption and loss of control over alcohol use. Adolescents, consuming a large amount of alcohol, are therefore at risk. To better understand the effect of age of onset on alcohol consumption and loss of control, this research tested the hypothesis that rats that started alcohol consumption in adolescence show less control loss, possibly due to increased cognitive flexibility, and are therefore less sensitive to develop alcohol addiction, using rats that started drinking at different ages. Methods: Male Lister Hooded rats were given access to alcohol on an intermittent-every-other-day basis. The groups, aged 35 (adolescent) and 70 days (adult), had a choice from two bottles (water and 20% alcohol solution). Afterwards the rats were divided into tertiles (low, medium and high drinkers) and trained in an operant box to self-administer alcohol. Subsequently, pairing took place, in different boxes, making the rats associate a mild footshock to a tone. Then a conditioned suppression test was executed to study whether the rats press equally when confronted with the tone and assess their loss of control over alcohol use. Results: A difference in alcohol intake (g/kg) was found, with adolescents having a higher intake in the first two weeks and adults the last four weeks of the voluntary intake period. Adult low drinkers reduce their seeking behaviour during the conditioned suppression test, whereas the high drinkers do not. The adolescent low drinkers show an overall lower press rate and no suppression of their seeking behaviour. High drinking adolescents on the other hand, press more and do adapt seeking behaviour in response to the footshock associated tone. Conclusion: The results suggest age of onset influences the alcohol consumption in rats, with after only one month adults having a steady higher intake. Adolescent high drinkers show no loss of control, however high drinking adults are more compulsive, which is a part of AUD. Further research on the specific neural background is needed for a better understanding on this behaviour.