Rationale: Anxiety and aggression are associated with ethanol self-administration, but these behaviors can serve as either risk factors for or consequences of heavy drinking in rodents and humans. Baseline levels of aggressive-like and anxious-like behavior in non-human primates have not yet been characterized in relation to future or prior ethanol intake.
Objective: The objective of the study was to test the association between temperament at baseline with future ethanol self-administration in late adolescent male (n = 21) and female (n = 11) rhesus monkeys.
Methods: Shortly after entering the laboratory and before exposure to ethanol, the Human Intruder Test (HIT) and the Novel Object Test (NOT) were used to determine baseline anxious-like and aggressive-like behavior in age-matched male and female rhesus monkeys (Macaca mulatta). The monkeys were induced to drink ethanol 4 % (w/v) using a schedule-induced polydipsia procedure, followed by "open-access" ethanol self-administration in which the monkeys were allowed a choice of water or 4 % ethanol (w/v) for 22 h/day for 52 weeks.
Results: Aggressive monkeys self-administered more ethanol and attained higher blood ethanol concentrations (BECs). No significant differences in ethanol intakes or BECs were found between anxious and non-anxious monkeys or between behaviorally inhibited and non-inhibited monkeys. Baseline aggressive behavior positively correlated with ethanol intake and intoxication.
Conclusions: Baseline reactive aggression was associated with higher future ethanol intake and intoxication. While significant sex differences in HIT reactivity were observed, the relationship between aggression and ethanol drinking was observed across sex and is not sex-specific.
Keywords: Aggression; Anxiety; Monkey; Risk factors; Sex differences; Temperament.