Aggressive behavioral phenotypes in mice

Aggressive behavior in male and female mice occurs in conflicts with intrud ing rivals, most often for the purpose of suppressing the reproductive succ ess of the opponent. The behavioral repertoire of fighting is composed of i ntricately sequenced bursts of species-typical elements, with the resident displaying offensive and the intruder defensive acts and postures. The prob ability of occurrence as well as the frequency. duration. temporal and sequ ential patterns of aggressive behavior can be quantified with ethological m ethods. Classic selection and strain comparisons show the heritability of a ggressive behavior, and point to the influence of several genes, including some of them on the Y chromosome. However, genetic effects on aggressive be havior critically depend upon the background strain, maternal environment a nd the intruder. These factors are equally important in determining changes in aggressive behavior in mice with a specific gene deletion. While change s in aggression characterize mutant mice involving a variety of genes, no p attern has emerged that links particular gene products (i.e. enzyme, peptid e, receptor) to either an increase or a decrease in aggressive behavior. bu t rather emphasizes polygenic influences. A potentially common mechanism ma y be some components of the serotonin system. since alterations in 5-HT neu rotransmission have been found in several of the KO mice that display unusu al aggressive behavior. (C) 2001 Elsevier Science B.V. All rights reserved.