Am J Psychiatry 1991; 148:1518-1525
Copyright © 1991 by American Psychiatric Association
Serotonin function and depression: neuroendocrine and mood responses to intravenous L-tryptophan in depressed patients and healthy comparison subjects
LH Price, DS Charney, PL Delgado and GR Heninger
Clinical Neuroscience Research Unit, Abraham Ribicoff Research Facilities, Connecticut Mental Health Center, New Haven.
OBJECTIVE: This study was designed to compare central serotonergic function
in depressed patients and healthy comparison subjects by examining
neuroendocrine and mood responses to intravenous L- tryptophan. METHOD: One
hundred twenty-six drug-free patients with DSM- III-R major depression (109
unipolar, 17 bipolar; 68 melancholic, 58 nonmelancholic; 28 psychotic, and
98 nonpsychotic patients) and 58 healthy comparison subjects participated.
After an overnight fast, subjects received an intravenous infusion of
L-tryptophan, 7 g. Blood was obtained for determination of serum prolactin,
serum growth hormone (GH), and plasma tryptophan levels. Visual analogue
scales were used to assess mood. RESULTS: Prolactin responses were blunted
in nonmelancholic and higher in melancholic and psychotic depressed
patients, while GH responses were blunted in combined unipolar,
nonmelancholic, and nonpsychotic depressed patients. Controlling for
baseline biological, clinical, and demographic factors eliminated the
higher prolactin response in the melancholic and psychotic patients,
attenuated the blunted GH response in the unipolar patients, and revealed a
blunted GH response in the melancholic patients. Patients and comparison
subjects differed on five of 13 mood responses, primarily because of
baseline differences. CONCLUSIONS: These findings are consistent with
previous studies demonstrating blunted neuroendocrine responses to
intravenous L-tryptophan in depression. Restriction of these findings to
specific subtypes of depression may reflect a differential role of
serotonergic abnormalities in these subtypes.
