Measurement of histamine metabolites in brain and cerebrospinal fluid provides insights into histaminergic activity.

Measurements of the concentrations of histamine's metabolites, tele-methylhistamine (t-MH) and tele-methylimidazoleacetic acid (t-MIAA), in brain have been used to evaluate histamine turnover in brains of animals, and the same measurements in CSF have been used to infer histaminergic activity in brains of man. In regions of rat brain, half-lives of histamine are shorter than those of dopamine, 5-hydroxytryptamine and norepinephrine. Studies of human CSF suggest that brain histaminergic activity increases with age and is higher in females than in males.