Effects of histamine H1- and H2-receptor antagonists on dopamine, noradrenaline and serotonin systems in rat brain

The action of histamine H1-receptor antagonists: chloropyramine (CIPYR), diphenhydramine (DPHA) and mepyramine (MEP), and histamine H2-receptor antagonist: burimamide (BUR), metiamide (MET) and cimetidine (CIM) and their methylated analogues methylburimamide (MeBUR) and thiaburimamide (ThBUR) on brain monoamines dopamine (DA), noradrenaline (NA) and serotonin (5HT) in the rat was investigated. H1-receptor antagonists CIPYR and DPHA did not significantly influence both DA disappearance after kappa-methyl-p-tyrosine and DOPAC levels in the rat striatum. DPHA had no significant effect on the striatal DA content while CIPYR decreased it. All of the tested H1-receptor antagonists increased both NA and 5HT levels and decreased 5-HIAA concentrations in the hypothalamus and the striatum. Large doses of H2-receptor antagonists (50-259 micrograms ivt) decreased hypothalamic NA content. One nanogram of BUR, MET and ThBUR in NA levels, while such low doses of MeBUR nd CIM did not affect the amine content in the rat hypothalamus, neither acute nor chronic treatment with CIN ip significantly influenced NA,DA and 5HT levels in the brain.