Mood, prolactin and cortisol responses following intravenous L-tryptophan challenge: evidence for serotonergic vulnerability in first-degree relatives of bipolar patients

Central serotonergic vulnerability indicated by altered mood and neuroendocrine responses to an intravenous (i.v.) tryptophan (Trp) challenge was assessed in healthy adult unaffected first-degree relatives of bipolar disorder (BD) patients ( n = 30) (family history; FH). The effects of a single dose of 7.0 g Trp on mood, cortisol and prolactin (Prl) in FH subjects were compared with healthy matched controls ( n = 15) in a placebo-controlled, double blind cross-over design. Prl and cortisol responses increased following Trp. Overall, Trp lowered mood. Hormonal and mood effects did not differ between FH and controls. Results show some evidence for differences in serotonergic vulnerability between relatives of type I BD patients and relatives of type II BD patients.