EFFECTS OF INTRACEREBROVENTRICULAR ADMINISTRATION OF N-ACETYLHISTAMINE ON BODY-TEMPERATURE IN MICE

The purpose of this study was to examine the effects of intracerebroventricular (i.c.v.) administration of N-acetylhistamine on rectal temperature, histamine level, histidine decarboxylase (HDC) activity, and the turnover rate of monoamines in mice. More than 60 mu g of N-acetylhistamine induced hypothermia. The maximum effect of hypothermia was observed 20 min after administration of N-acetylhistamine (60-120 mu g/mouse). A significant drop in rectal temperature of 3 degrees C was induced by 120 mu g of N-acetylhistamine Concurrent with the appearance of hypothermia, the histamine levels were increased. However both histamine H-1 and H-2 antagonists did not prevent hypothermia. The i.c.v. administration of N-acetylhistamine inhibited HDC activity, but had no effect on the turnover rates of monoamines. These data confirmed that endogenous N-acetylhistamine may be a metabolite which lacks significant physiological roles, and demonstrated that exogenous N-acetylhistamine is not a good pharmacological tool for the study of the functions of the brain histaminergic system in mammals.