This is consistent with the recent clinical finding that a polymorphism of the 5-HT 1B receptor gene is associated with antisocial alcoholism in humans. Altered serotonin function during brain development may alter the final product of that development. It is impossible to say what the lack of 5-HT 1B receptors during development may do to serotonergic function in adults. If knockout mice with decreased brain serotonin function exhibit increased aggression, then knockouts with increased serotonin function might be expected to have decreased aggression. This may be due to subtle alterations in brain development.
Aggressive impulses are under inhibitory control by higher brain areas.
Factors that interfere with normal brain development sometimes interfere as well with the inhibition of aggression. Thus, it is not particularly surprising that a variety of knockout mice exhibit aggression. Not all knockouts increase aggression. Nonetheless, the wide range of knockout mice that exhibit increased aggression casts doubt on the specificity of the relation between 5-HT 1B receptors and aggression. What is needed in the short term is an animal model in which a gene is active in the developing organism, but can be turned off in the adult.