Aggressive behaviour and the central serotonergic systems.

A brief critical review of serotonin involvement in two classes of aggressive behaviour, i.e. affective and predatory aggression, is presented. Special emphasis is put on the differentiation between the role played in aggression by the two ascending serotonergic systems, the mesolimbic and the mesostriatal. It is concluded that only serotonergic neurons from the dorsal raphe nucleus forming the mesostriatal system play an inhibitory role in both classes of aggression. The mesolimbic system does not seem to be directly involved in an aggression modulation. The data suggesting that the dorsal raphe may mediate its inhibitory influence through the medial amygdala is presented and discussed. Finally some attention is given to the problem of serotonin metabolism variability (biorhythm) and its implications in behavioural studies.