Amelioration of psychosis with carbidopa. A case report

The trace amines and their acidic metabolites in depression--an overview

1. Investigations of the role of the trace amines (phenylethylamine, tryptamine, m- and p-tyramine) and their acidic metabolites (phenylacetic, indoleacetic, m- and p-hydroxyphenylacetic acids) in depression are reviewed. 2. The evidence for the phenylethylamine hypothesis of depression is mixed. 3. Reduced phenylacetic acid levels in urine, plasma and CSF and changes in those levels during treatment with antidepressants show potential as state markers for depression. 4. Impaired p-tyramine conjugation following a tyramine challenge may be a good trait marker for depression.

Trace amines and Tourette's syndrome

There has been considerable interest in recent years in possible neurochemical abnormalities in Tourette's Syndrome (TS). In studies combining neuropsychological and neurochemical measurements, we have investigated the possible roles of trace amines in this disorder. Urinary levels of free beta-phenylethylamine (PEA) and plasma levels of its precursor amino acid phenylalanine were decreased in TS patients when compared to values in normal children. These urinary PEA levels in TS patients were inversely related to several scores from the Tourette's Syndrome Global Scale (TSGS). Further investigation of the group of subjects with low urinary PEA indicated that they also had low levels of MHPG, normetanephrine, 5-HT and m- and p-tyramine. Patients with low PEA were also compared on an extensive battery of neuropsychological measures and observed to perform significantly worse than TS patients with normal urinary PEA levels. Biochemical measurements also suggest a possible abnormality in tryptamine turnover in TS since urinary levels of indole-3-acetic acid (IAA; the acid metabolite of tryptamine) are significantly lower in TS patients than in normal controls.

Phenylethylamine excretion in depression

Urinary phenylethylamine (PEA) excretion was evaluated in two populations of depressed hospitalized patients. Seven of 53 patients had PEA values exceeding three times the highest value found in 16 normal controls. The patients with high PEA excretion were all females. They were not, however, otherwise clinically distinguishable from depressed patients with low PEA. In a subsample of 31 patients and 10 controls, PEA excretion was not correlated with phenylacetic acid (PAA) excretion. These results suggest that depression is not associated with a generalized PEA deficit and that PAA reductions, previously reported in a depressed patient population, may not reflect a PEA abnormality.