Trait hostility and prolactin response to tryptophan enhancement/depletion

This study investigated the relationship between trait hostility and aspect s of serotonergic function by assessing the prolactin (PRL) response to acu te tryptophan depletion and enhancement in 28 healthy male volunteers. Seru m PRL was assessed immediately before, and 4.5 h after, administration of a n amino acid drink enhanced with, or depleted of, the 5-HT precursor trypto phan. Trait hostility and Delta PRL (value at 4.5 h minus baseline) correla ted negatively following enhancement and positively following depletion, in dicating that the higher the hostility the smaller the change in PRL in eit her direction. This is consistent with previous research reporting an assoc iation between aggression and blunted neuroendocrine responses to serotoner gic agents. The results indicate the possibility that, in people high on ho stility, part of the serotonergic pathway that leads to modulation of PRL r elease is characterised by a stage with either low capacity relative to inp ut availability or a strong negative feedback component.