ABOUT THE BIOLOGICAL
Herman M. van Praag
In 1970 we reported evidence suggesting a reduced metabolism of serotonin (5 -hydroxytryptamine; 5-HT) in a subgroup of depression. As shown in Figure 4.1, we found lowered concentrations of the main metabolite of 5-HT, 5-hydroxyindoleacetic acid (5-HIAA), in the cerebrospinal fluid (CSF) of a subgroup of depressed patients (Van Praag et al, 1970). As CSF 5-HIAA and intra-cerebral 5-HIAA concentration are highly correlated, both in animals and in humans (Mignot et al, 1985; Stanley et al, 1985), CSF 5-HIAA can be regarded as a (crude) indicator of 5-HT breakdown in the brain.
Low-CSF 5-HIAA appeared not to be correlated with a particular subtype of depression, such as bipolar or unipolar depression, or with a particular depressive syndrome, such as the syndrome of vital (endogenous, melancholic) depression. Low-CSF 5-HIAA was demonstrated to be functionally specific, as it was associated with components of the depressive syndrome, which may or may not be prominently present in a particular depressive state. These 5-HT-linked features were: disturbances in the regulation of anxiety and of aggression