Rostral-caudal concentration gradients of histamine metabolites in human cerebrospinal fluid

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Abstract
The metabolites of histamine,tele-methylhistamine (t-MH) andtele-methylimidazoleacetic acid (t-MIAA), have a large concentration gradient between cisternal and lumbar CSF in the rhesus monkey. The possibility of a t-MH and/or t-MIAA gradient in man was studied in sequential samples of CSF withdrawn from the lumbar space from a healthy male. The mean levels of t-MH and t-MIAA in the 14–16 ml segment of CSF from 6 male volunteers was also measured.pros-Methylimidazoleacetic acid (p-MIAA), an endogenous isomer of t-MIAA that is not derived from histamine, was also measured. Levels of t-MH, t-MIAA and p-MIAA were measured by gas chromatography-mass spectrometry. With increasing volumes of CSF removed, t-MH and t-MIAA levels increased linearly (p0.6) in serially removed CSF; the individual levels in CSF from the volunteers on unrestricted diets varied widely, suggestive of a dietary influence on p-MIAA levels in the CNS. The concentration gradient of histamine metabolites in CSF confirms the rostral-caudal gradient observed in monkey and argues against plasma or spinal cord as major sources of these metabolites. The significant gradients for t-MH and t-MIAA, but not p-MIAA, suggest that the rostral-caudal gradient of histamine metabolites reflect histamine metabolism at rostral sites, presumably the brain.