DIURNAL AND AGE-RELATED-CHANGES IN CEREBROSPINAL-FLUID TELE-METHYLHISTAMINE LEVELS DURING INFANCY AND CHILDHOOD

Histamine is a neurotransmitter participating in many physiological fu nctions and behavior, including control of arousal and modulation of t he circadian rhythms. Diurnal variation in cerebrospinal fluid (CSF) l evels of tele-methylhistamine (t-MH), the main histamine metabolite, h as been detected in several animal studies. In humans, such changes ha ve not been described. Little is known on the development of histamine rgic neurons in human brain. In children, the levels of CSF t-MH are n ot known. Therefore, we have measured the concentrations of CSF t-MH i n 81 children, age ranging from 3 months to 14.6 years, t-MH levels we re higher in infants, and near adult values were measured in adolescen ts, the relation between CSF t-MH and age being; CSF t-MH = -0.217 yea r + 7.31 (n = 81, r = 0.26, p = 0.021). The mean t-MH concentration wa s higher during the daytime (7.07 +/- 0.46 pmol/ml, mean +/- SEM) than in the night (5.35 +/- 0.60 pmol/ml, p = 0.0019, ANOVA). The results show a developmental change in the concentration of t-MH during childh ood and a difference in t-MH levels between the daytime and night indi cating a more active metabolism of brain HA in the waking period.