The histamine H4 receptor is a novel G-protein-coupled receptor with a unique pharmacological profile. The distribution of H4 mRNA suggests that it may play a role in the regulation of immune function, particularly with respect to allergy and asthma. To define the histamine-binding site of this receptor, molecular modeling and site-directed mutagenesis were used to predict and alter amino acids...

Histamine influences the glomerular microcirculation and modulates immune-inflammatory responses. In the rat kidney, histamine is synthesized by glomeruli and stimulates cyclic nucleotide production specifically in glomeruli. We investigated the in vitro effect of histamine on cyclic nucleotide accumulation in rat cultured glomerular mesangial and epithelial cells. Histamine stimulated cyclic A...

Histamine causes vasodilation in the dog by activation of H1 and H2 receptors blocked by mepyramine and metiamide, respectively. Experiments were conducted in anesthetized dogs to determine the participation of H1 and H2 receptors in several forms of physiological dilatation. Mepyramine attenuated both histamine-induced and active-reflex dilatation in the hindlimb. Metiamide caused a further re...

H1 and H2 histamine receptor antagonists, although developed many decades ago, are still effective for the treatment of allergic and gastric acid-related conditions. This article focuses on novel aspects of the pharmacology and molecular mechanisms of histamine receptors that should be contemplated for optimizing current therapies, repositioning histaminergic ligands for new therapeutic uses, o...

The effects of both an H1 receptor antagonist and an H2 receptor antagonist on changes in monovalent ion flux induced by topical sodium taurocholate were studied in antrectomised dogs fashioned with a denervated fundic pouch. The magnitude of taurocholateinduced ion flux was unaffected by topical administration of H1 or H2 receptor antagonists. Parenteral administration of H1 or H2 receptor ant...

The effects of both an H1 receptor antagonist and an H2 receptor antagonist on changes in monovalent ion flux induced by topical sodium taurocholate were studied in antrectomised dogs fashioned with a denervated fundic pouch. The magnitude of taurocholate-induced ion flux was unaffected by topical administration of H1 or H2 receptor antagonists Parenteral administration of H1 or H2 receptor ant...

To determine if histamine acts directly on the vascular endothelium, the effect of histamine on the permeability of cultured human endothelial cell monolayers and the role of second messengers were examined. The addition of 10(-6) to 10(-4) M histamine to the culture medium decreased the endothelial cell monolayer permeability and increased both cyclic AMP and free-calcium levels. The decrease ...

The effect of intraventricular histamine on blood flow in the caudate nucleus of the cat was studied by means of the hydrogen clearance technique. Bilateral ventriculo-cisternal perfusion was installed. After a control period during which both lateral ventricles were perfused with mock CSF with the same composition, the drug under study was added to one side (experimental side) while the other ...