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.
Perphenazine is a typical antipsychotic drug, inhibits 5-HT2A receptor (5-HT2A), Alpha-1A adrenergic receptor (α1A), Dopamine receptor D2/D3, D2L receptor, and Histamine H1 receptor (H1) with Ki of 5.6, 10, 0.765/0.13, 3.4, and 8 nM.
Promethazine Hcl(NSC-231688) 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.
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.
Diphenylpyraline Hcl is a first-generation antihistamine with anticholinergic effects, acts as a dopamine reuptake inhibitor, shows to be useful in the treatment of Parkinsonism.
Fexofenadine is a third-generation antihistamine pharmaceutical drug used in the treatment of allergy symptoms, such as hay fever, nasal congestion, and urticaria.
