ABSTRACTIntroductionPeer interactions are a crucial part of social and personal development, particularly during adolescence. Adolescence is characterized as a transitional developmental period between childhood and adulthood that is often associated with increased freedom, self-exploration, and novel experiences that are frequently peer-influenced. Due to newfound independence, there is a higher prevalence of alcohol consumption, which is in part due to the heightened social facilitating and rewarding effects of alcohol. Previous work shows that males and females who consume excessive alcohol during adolescence are at an increased risk of developing an alcohol use disorder (AUD) later in life. However, the contributions of social interaction and sexual dimorphism in alcohol consumption, two driving factors that influence AUD risk, are not fully understood. Many current rat models used to study the characteristics of alcohol use and the emergence of AUD coerce the animals into consuming liquid ethanol by the addition of a sweetener, which has been proven to confound results in adolescent rats. Here we use a novel self-administration ethanol vapor system to investigate the sexual dimorphic nature of socially facilitated ethanol consumption without the addition of sweeteners.MethodsAdolescent and adult male and female Sprague-Dawley rats underwent a novel voluntary chronic intermittent self-administration ethanol vapor paradigm. Nose poke-initiated self-administration vapor chambers (La Jolla Alcohol Research, Inc.) administered 20mg/L of vaporized ethanol or air (control) into the chamber in response to each individual nose poke. Beginning on postnatal day (PND) 30 or PND70, animals were placed in vapor chambers for 4 hours every other day for a total of 40 sessions. All animals underwent 10 sessions with their cagemate (social access) followed by 10 sessions in isolation (isolated access), a 10 day forced abstinence period, 10 sessions in isolation (isolated access), and 10 sessions with their cagemate (social access).ResultsFemale rats consumed more alcohol per body weight than age-matched males, while male rats increased ethanol preference over sessions regardless of age. In addition, all rats regardless of sex or age consumed more ethanol per body weight during the first social access session than during the subsequent isolated access sessions. Interestingly, there was an increase in ethanol consumption in adult male and females during the second social access session compared to the previous isolated access session that was not observed in either adolescent groups.ConclusionThese data demonstrate that female and male rats, regardless of age, are vulnerable to socially facilitated ethanol consumption. This is consistent with human data showing that increased levels of alcohol consumption among adolescents and young adults is associated with high levels of alcohol use within their social group (Sudhinaraset, Wigglesworth, & Takeuchi, 2016). However, only male rats demonstrate escalation across sessions. This may indicate that male rats are more vulnerable to escalated drinking and the emergence of ethanol dependence compared to females regardless of peer interaction. These data demonstrate that the self-administration ethanol vapor system is an effective alternative to other methods of voluntary ethanol administration for investigating factors that contribute to alcohol use and escalation.
Intermittent voluntary ethanol consumption combined with ethanol vapor exposure during adolescence increases drinking and alters other behaviors in adulthood in female and male rats
