No abstract

Similar to metabolites of other aminergic transmitters, histamine metabolites of brain, tele-methylhistamine (t-MH) and tele-methylimidazoleacetic acid (t-MIAA), could have a concentration gradient between rostral and caudal sites of CSF. To test this hypothesis, cisternal and lumbar CSF samples were collected in pairs from eight monkeys (Macaca mulatta), and levels of t-MH and t-MIAA were measured by gas chromatography-mass spectrometry. pros-Methylimidazoleacetic acid (p-MIAA), an endogenous isomer of t-MIAA that is not a histamine metabolite, was also measured. Cisternal levels (in picomoles per milliliter, mean +/- SEM) of t-MH (9.9 +/- 1.4) and t-MIAA (40.8 +/- 7.6), but not of p-MIAA (9.7 +/- 1.2), exceeded those in lumbar CSF (t-MH, 1.8 +/- 0.3; t-MIAA, 6.8 +/- 0.9; p-MIAA, 8.6 +/- 0.6) in every monkey. The magnitudes of the mean cisternal-lumbar concentration gradients for t-MH (6.6 +/- 1.1) and t-MIAA (6.5 +/- 1.3) were indistinguishable. These gradients exceed those of metabolites of most other transmitters. There was no gradient for the levels of p-MIAA. The cisternal, but not lumbar, levels of t-MH and t-MIAA were correlated. There was no significant difference between the means of the metabolite concentration ratios (t-MIAA/t-MH) in cisternal (4.0 +/- 0.4) and lumbar (4.4 +/- 0.9) CSF. The steepness of these gradients suggests that levels of t-MH and t-MIAA in lumbar CSF might be useful probes of histaminergic metabolism in brain.