Acid metabolites and precursor amino acids of 5-hydroxytryptamine and dopamine in affective and other psychiatric disorders.

Levels of various compounds related to monoamines were assessed in 96 patients with a variety of depressive and nondepressive syndromes. The diagnostic categories were composed retrospectively after examination of International Classification of Diseases (ICD) classifications and all available data in medical reports. All patients underwent the 8-hour probenecid test. Administration of probenecid was partly intravenous (1 g) and partly oral (4 g). In all patients, the cerebrospinal fluid (CSF) levels of 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA), and probenecid were estimated, while in about half of the patients tryptophan and tyrosine were determined in CSF and serum. When the group is taken as a whole, significant positive correlations are found between the CSF levels of 5-HIAA, HVA and probenecid, between the CSF levels of tryptophan and tyrosine, and between tyrosine levels in serum and CSF. A negative correlation is found between CSF probenecid and serum tryptophan. The group of patients was divided in several ways into various subgroups. Analysis of covariance of clinical and biochemical data indicates no significant biochemical differences between any of the subgroups. This retrospective study lacks supportive evidence that any of the clinical syndromes, including the depressive syndromes, is characterized by specific deficiencies of monoamine neurotransmission.