Isolation rearing (IR) enhances aggressive
behavior, and the central
serotonin (
5-hydroxytryptamine,
5-HT) system has been linked to IR-induced
aggression. However, whether the alteration of central
serotonin is the cause or consequence of enhanced
aggression is still unknown. In the present study, using
mice deficient in central
serotonin Tph2 and Lmx1b, we examined the
association between central
serotonin and
aggression with or without
social isolation. We demonstrated that central
serotonergic neurons are critical for the enhanced
aggression after IR.
5-HT depletion in wild-type
mice increased
aggression. On the other
hand, application of
5-HT in Lmx1b
mice inhibited the enhancement of
aggression under
social isolation conditions.
Dopamine was downregulated in Lmx1b
mice.
Similar to
5-HT,
L-DOPA decreased
aggression in Lmx1b
mice. Our results link the serotoninergic system directly to
aggression and this may have clinical implications for
aggression-related
human conditions.