( ientists videotaped the encounters to d...)Adolescent but not adult hamsters are more aggressive on low dose of fluoxetine

The adult hamsters treated with either dose of fluoxetine became generally more peaceful, attacking less often and for shorter times. However, the juveniles responded differently, both to high and low doses. The low doses actually resulted in significantly longer, more frequent and intense attacks, whereas the high dose only partly inhibited aggression. Neither set of juveniles responded as well as adults; one set (low dose) actually did worse.

Thus, although fluoxetine consistently calmed the adults in a potentially threatening situation, it differentially affected the juveniles. The effects of fluoxetine on aggressive responses appear to be specific to both age and dose.

The authors say their data add to growing evidence that during puberty, the brain is still maturing and, says Taravosh-Lahn, "could possibly react to drugs given to adults in different and potentially negative ways. We need to understand how these drugs will affect the developing nervous system before giving them to children."

The neuroscientists explain that because adolescents may have lower levels of serotonin than adults, there may not be enough of it in their systems for the SSRI to work effectively. In addition, the researchers are investigating whether changing ratios of different subtypes of serotonin receptors ?some of which inhibit and some of which enhance aggression -- are implicated in the findings of higher aggression on low doses.
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Source:American Psychological Association