Increased aggression after ethanol self-administration in male resident rats

Abstract

In order to study experimental alcohol intake that leads to heightened aggression, we established ethanol self-administration in aggressive rats. The focus was on low doses of self-administered ethanol and to assess their effects on aggressive behavior in resident rats, using a limited access paradigm followed by a 5-min confrontation with an intruder. In the first phase of the experiment, rats were established as "residents", and their consistent aggressive behavior in confrontations with an intruder was verified. In the second phase, these resident rats were trained to self-administer alcohol, using a sucrose-fading technique. In the third phase, alcohol self-administration was followed by intruder confrontations in order to study the effect of alcohol on aggression. Confrontations after ethanol consumption leading to low (5-20 mg/dl) and moderate (20-50 mg/dl) blood alcohol concentration (BAC) were compared to confrontations without alcohol, each animal serving as its own control. On average, the group showed no change in aggressive behavior after low or moderate ethanol intake. However, six out of 16 individuals significantly increased the number of attack bites and the duration of aggressive behavior by up to 90% after alcohol self-administration. When these rats were assigned post-hoc to an alcohol heightened aggression group, the group was characterized by a 40% increase in number of attack bites and a 90% increase in aggressive posture over control (BAC 0 mg/dl), whereas the alcohol non-heightened aggression group showed no significant changes. These results extend previous observations of increased aggression in a subpopulation of animals after experimenter-administered ethanol in mice, rats and monkeys to self-administered alcohol. Using this animal model, individuals showing enhanced or reduced aggression after oral alcohol self-administration can be characterized behaviorally, physiologically, and neurochemically.

Repeated alcohol: behavioral sensitization and alcohol-heightened aggression in mice

“…alcohol administrations which also induced locomotor sensitization. Previous studies on alcohol-heightened aggression in monkeys, rats, and mice have identified sub-groups of individuals that are consistently more aggressive after alcohol (approximately 25% of mice; Weerts et al 1993a;van Erp and Miczek 1997;Miczek et al 1998). Alcohol-heightened aggression has been considered a trait characteristic because it is repeatable over time (Miczek et al 1998).…”

“…Preclinical research has identified similar individual differences in alcohol-heightened aggression using several animal species (Peeke and Figler 1981;Miczek et al 1992Miczek et al , 1998Weerts et al 1993a;van Erp and Miczek 1997). Genetic variation has been hypothesized to explain why some individuals are more vulnerable than others to alcohol-heightened aggression.…”

Aggression heightened by alcohol or social instigation in mice: reduction by the 5-HT1B receptor agonist CP-94,253

“…The 2 SD criterion that is used to identify this population is based on the principle that AHA animals represent statistical outliers (Barnett and Lewis 1984). In rats, alcohol heightened aggression can be brought about by either experimenter-administered or self-administered oral ethanol (van Erp and Miczek 1997). In view of the relevance to the human condition, it would be desirable to study alcohol heightened aggression in animals that self-administer alcohol.…”

GABAA/α1 receptor agonists and antagonists: effects on species-typical and heightened aggressive behavior after alcohol self-administration in mice

“…Characteristically, alcohol as well as other positive modulators of the GABA A receptor increase the frequency and duration of aggressive behavior far in excess of the species-typical level at lower and moderate doses, whereas sedative effects prevail at higher doses (Raynes and Ryback 1970;Chance et al 1973;Miczek and Barry 1977;Peeke et al 1981;Blanchard et al 1987;Weerts and Miczek 1996;Van Erp and Miczek 1997). While this alcohol effect is large in magnitude, it is consistently restricted to approximately 20-30% of all animals tested (Miczek et al 1992(Miczek et al , 1998.…”