Positron emission tomography measurement of cerebral metabolic correlates of tryptophan depletion-induced depressive relapse

Arch Gen Psychiatry. 1997 Apr;54(4):364-74. doi: 10.1001/archpsyc.1997.01830160092012.


Background: Short-term depletion of plasma tryptophan has been shown to result in depressive relapse in patients with remission of major depression. Positron emission tomography and single photon emission computed tomography studies implicated the dorsolateral prefrontal cortex, orbitofrontal cortex, thalamus, and caudate nucleus in the pathogenesis of depression. The purpose of this study was to measure cerebral metabolic correlates of tryptophan depletion-induced depressive relapse.

Methods: Patients diagnosed as having major depression (N = 21) who clinically improved with serotonin reuptake inhibitors underwent 2 test days involving tryptophan depletion or placebo, followed 6 hours later by positron emission tomography scanning with fludeoxy-glucose F18. Brain metabolism was compared in patients with (n = 7) and without (n = 14) a tryptophan depletion-induced depressive relapse.

Results: Tryptophan depletion resulted in a decrease in brain metabolism in the middle frontal gyrus (dorsolateral prefrontal cortex), thalamus, and orbitofrontal cortex in patients with a depletion-induced depressive relapse (but not in patients without depletion-induced relapse). Decreased brain metabolism in these regions correlated with increased depressive symptoms. Baseline metabolism was increased in prefrontal and limbic regions in relapse-prone patients.

Conclusion: Specific brain regions, including the middle frontal gyrus, thalamus, and orbitofrontal cortex, may mediate the symptoms of patients with major depression.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Antidepressive Agents / therapeutic use
  • Brain / diagnostic imaging*
  • Brain / metabolism
  • Brain / physiopathology
  • Deoxyglucose / analogs & derivatives
  • Depressive Disorder / diagnostic imaging*
  • Depressive Disorder / drug therapy
  • Depressive Disorder / physiopathology*
  • Double-Blind Method
  • Fluorodeoxyglucose F18
  • Glucose / metabolism
  • Humans
  • Limbic System / diagnostic imaging
  • Limbic System / metabolism
  • Limbic System / physiopathology
  • Placebos
  • Prefrontal Cortex / metabolism
  • Prefrontal Cortex / physiopathology
  • Psychiatric Status Rating Scales
  • Recurrence
  • Serotonin / physiology*
  • Thalamus / diagnostic imaging
  • Thalamus / metabolism
  • Thalamus / physiopathology
  • Tomography, Emission-Computed*
  • Tryptophan / administration & dosage
  • Tryptophan / blood
  • Tryptophan / metabolism*


  • Antidepressive Agents
  • Placebos
  • Fluorodeoxyglucose F18
  • Serotonin
  • Tryptophan
  • Deoxyglucose
  • Glucose