Histamine Receptors are a class of G protein-coupled receptors with histamine as their endogenous ligand. There are four known histamine receptors: H1 receptor, H2 receptor, H3 receptor, H4 receptor. The H1 receptor is a histamine receptor belonging to the family of Rhodopsin-like G-protein-coupled receptors. This receptor, which is activated by the biogenic amine histamine, is expressed throughout the body, to be specific, in smooth muscles, on vascular endothelial cells, in the heart, and in the central nervous system. H2 receptors are positively coupled to adenylate cyclase via Gs. It is a potent stimulant of cAMP production, which leads to activation of Protein Kinase A. Histamine H3 receptors are expressed in the central nervous system and to a lesser extent the peripheral nervous system, where they act asautoreceptors in presynaptic histaminergic neurons, and also control histamine turnover by feedback inhibition of histamine synthesis and release. The Histamine H4 receptor has been shown to be involved in mediating eosinophil shape change and mast cell chemotaxis.
Histamine is an organic nitrogenous compound involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter.
Astemizole (R 43512), a second-generation antihistamine drug to diminish allergic symptoms with a long duration of action, is a histamine H1-receptor antagonist, with an IC50 of 4 nM. Astemizole also shows potent hERG K+ channel blocking activity with an IC50 of 0.9 nM. Astemizole has antipruritic effects.
Carebastine is the active metabolite of Ebastine. Carebastine is a histamine H1 receptor antagonist. Carebastine inhibits VEGF-induced HUVEC and HPAEC proliferation, migration and angiogenesis in a dose-dependent manner. Carebastine suppresses the expression of macrophage migration inhibitory factor.
Pimethixene maleate is antihistamine and antiserotonergic compound, acts as an antimigraine agent.
Pimethixene maleate is a highly potent antagonist of 5-HT1A, 5-HT2A, 5-HT2B, 5-HT2C, histamine H1, dopamine D2 and D4.4 as well as muscarinic M1 and M2 receptors, with pKis of 7.63, 10.22, 10.44, 8.42, 10.14, 8.19, 7.54, 8.61 and 9.38, respectively.
Terfenadine ((±)-Terfenadine) is a potent open-channel blocker of hERG with an IC50 of 204 nM. Terfenadine, an H1 histamine receptor antagonist, acts as a potent apoptosis inducer in melanoma cells through modulation of Ca2+ homeostasis. Terfenadine induces ROS-dependent apoptosis, simultaneously activates Caspase-4, -2, -9 and induces p73, Noxa.
Fexofenadine hydrochloride (MDL-16455 hydrochloride), a H1R antagonist, is an anti-allergic agent used in seasonal allergic rhinitis and chronic idiopathic urticarial (person aged ≥16 years).
Latrepirdine dihydrochloride is a neuroactive compound with antagonist activity at histaminergic, α-adrenergic, and serotonergic receptors. Latrepirdine stimulates amyloid precursor protein (APP) catabolism and amyloid-β (Aβ) secretion.
Mepyramine maleate, a first generation antihistamine, is an antagonist of histamine H1 receptor, with Kds of 0.8 nM, 5200 nM and >3000 nM for H1, H2, and H3 receptor, respectively, and a pKd of 9.4 for H1 receptor.
Promethazine hydrochloride is the first-generation antihistamine; strong antagonist of the H1 receptor and moderate mACh receptor antagonist, moderate affinity for 5-HT2A, 5-HT2C, D2 and α1-adrenergic receptors.
Cetirizine dihydrochloride, a second-generation antihistamine, is a major metabolite of hydroxyzine, and a racemic selective H1 receptor inverse agonist used in the treatment of allergies, hay fever, angioedema, and urticaria.
Cinnarizine is an antihistamine and a calcium channel blocker, promote cerebral blood flow, used to treat cerebral apoplexy, post-trauma cerebral symptoms, and cerebral arteriosclerosis.
