Sex and age specific effects on the development of addiction and compulsive-like drinking in rats

Biological factors are known to influence disease trajectories and treatment effectiveness in alcohol addiction. One important biological factor influencing disease dynamics in alcohol use disorder is sex, as preclinical and clinical evidence suggests that gender influences disease trajectories in subjects with alcohol use disorder. Another critical factor is age at first intoxicating drink, which has been identified as a risk factor for later alcohol binging. Preclinical research allows prospective monitoring of rodents throughout the lifespan, providing very detailed information that cannot be acquired in humans. Lifetime monitoring in rodents can be conducted under highly controlled conditions, during which one can systematically introduce multiple biological and environmental factors that impact behaviors of interest. Here, we used the alcohol deprivation effect (ADE) rat model of alcohol addiction in a computerized drinkometer system to study disease dynamics and transition points of addictive behavior in cohorts of adolescent vs. adult as well as male vs. female rats in direct comparison. Early age of onset of drinking (postnatal day 40) in male rats had surprisingly little impact on the development of drinking behavior and compulsivity (quinine taste adulteration) when compared to rats that started drinking during early adulthood (postnatal day 72). However, female rats showed a stronger resistance to quinine taste adulteration after a history of ADEs, indicative of more pronounced compulsive behavior in females as compared to male rats. Specifically, female rats exhibit during quinine taste adulteration a higher frequency of drinking events and a larger access size, especially from the 20% alcohol solution, resulting in fast intoxication despite taste aversion in a relapse-like situation. Our results suggest that drinking patterns, and specifically solution preference as well as access size, provide a valuable indication into determining compulsive drinking. These findings provide a better understanding of sex and age factors involved in the development of drinking behavior that are important in preclinical development of models of addiction, drug development and exploration options for new treatments.