Whether the job is waking the brain after a peaceful sleep, initiating gastric secretion when dinner is served or orchestrating the elements of inflammation after a mosquito bite, histamine has been a known biological messenger for decades (Green, 1964; Eichler and Farah, 1966). At the end of the twentieth century, in the midst of the genomics and bioinformatics revolution, researchers in this ...

Histamine is an accepted neurotransmitter and/or neuromodulator in the central nervous system (CNS). Its neuronal system in the brain is well organized, with cell bodies localized in a small area of the posterior hypothalamus. Diverse biological actions of histamine are mediated via three classes of receptors termed H1, H2, and H3. The existence of other histamine receptor subtypes is likely in...

Histamine, a well-known inflammatory mediator, has been implicated in various immunoregulatory effects that are poorly understood. Thus, we tested the hypothesis that histamine inhibits the release of a proinflammatory cytokine, namely TNF, by stimulating the release of an anti-inflammatory cytokine, IL-10. Alveolar macrophages (AMs) from humans, Sprague Dawley rats, and the AM cell line, NR838...

The histamine H3 receptor agonist (R)alpha-methylhistamine (MeHA) inhibited, in a nanomolar range, basal and carbachol-stimulated inositol phosphate formation in the human gastric tumoral cell line HGT1-clone 6. The inhibition was reversed by micromolar concentrations of the histamine H3 receptor antagonist thioperamide and was sensitive to cholera or pertussis toxin treatment. Using [3H]N alph...

The role of neuronal histamine in memory processing. Neuronal histamine(HA) may play a role in memory processing. This hypothesis is based upon evidence that the action of histamine at central H1 and H2 histamine receptor sites has been shown to modulate memory of rats and mice in adversely-motivated tasks. The purpose of this study was to test this hypothesis more thoroughly in mice using two ...

We report the discovery, tissue distribution and pharmacological characterization of a novel receptor, which we have named H4. Like the three histamine receptors reported previously (H1, H2, and H3), the H4 receptor is a G protein-coupled receptor and is most closely related to the H3 receptor, sharing 58% identity in the transmembrane regions. The gene encoding the H4 receptor was discovered i...

Clozapine and olanzapine behave as weak H3-receptor antagonists in vitro with Ki values around 1 and 50 microM, respectively. Despite these modest apparent affinities, both compounds given orally to mice, nearly doubled steady-state tele-methylhistamine levels in brain, with ED50 values as low as 1 and 3 mg/kg, respectively, an effect comparable to those of potent H3-receptor antagonists. This ...

The role of central and peripheral histamine H3 receptors in the regulation of gastric acid secretion and gastric mucosal integrity is reviewed. The activation of H3 receptors by peripheral administration of the selective agonist (R)alpha-methylhistamine reduced acid secretion in cats, dogs, rats and rabbits, while increasing it in mice. The antisecretory effects were observed against indirect ...