THE effects of neonatal hydrocephalus on the levels of tyrosine, trypt
ophan, 5-hydroxyindoleacetic acid (5-HIAA), and homovanillic acid (HVA
) in CSF were determined by high-performance liquid chromatography (HP
LC) with fluorometric detection in normal and chronically hydrocephali
c rabbits. The hydrocephalic rabbits showed a highly significant incre
ase in both the serotonin metabolite 5-HIAA and the dopamine metabolit
e HVA. There were no significant effects of the hydrocephalus on eithe
r tyrosine or tryptophan levels. There was a significant positive corr
elation between the intracranial pressure (ICP) and the increase in 5-
HIAA and HVA, but not with the two precursor amino acids. There was a
significant decrease in these amino acid precursors with age in both g
roups. A trend towards higher levels of 5-HIAA and HVA in older rabbit
s was also evident, however this change was not to the degree found in
the hydrocephalics. These data indicate that increased ICP affects th
e mechanism of removal of 5-HIAA and HVA from the cerebrospinal fluid.