Search results
Results From The WOW.Com Content Network
The H 1 receptor is a histamine receptor belonging to the family of rhodopsin-like G-protein-coupled receptors. This receptor is activated by the biogenic amine histamine . It is expressed in smooth muscles , on vascular endothelial cells , in the heart, and in the central nervous system .
Histamine receptors are proteins that bind with histamine, a neurotransmitter involved in various physiological processes. There are four main types: H1, H2, H3, and H4. H1 receptors are linked to allergic responses, H2 to gastric acid regulation, H3 to neurotransmitter release modulation, and H4 to immune system function.
H 1 antagonists, also called H 1 blockers, are a class of medications that block the action of histamine at the H 1 receptor, helping to relieve allergic reactions.Agents where the main therapeutic effect is mediated by negative modulation of histamine receptors are termed antihistamines; other agents may have antihistaminergic action but are not true antihistamines.
H 1-antihistamines work by binding to histamine H 1 receptors in mast cells, smooth muscle, and endothelium in the body as well as in the tuberomammillary nucleus in the brain. Antihistamines that target the histamine H 1-receptor are used to treat allergic reactions in the nose (e.g., itching, runny nose, and
The K i values for the H 1 receptor are approximately 6 nM for cetirizine, 3 nM for levocetirizine, and 100 nM for dextrocetirizine, indicating that the levorotatory enantiomer is the main active form. [3] Cetirizine has 600-fold or greater selectivity for the H 1 receptor over a wide variety of other sites, including muscarinic acetylcholine ...
A histamine agonist is a drug which causes increased activity at one or more of the four histamine receptor subtypes. H 1 agonists promote wakefulness. [1] H 2: Betazole and Impromidine are examples of agonists used in diagnostics to increase histamine. H 3: Betahistine is a weak Histamine 1 agonist and a very strong antagonist of the Histamine ...
Diphenhydramine, while traditionally known as an antagonist, acts primarily as an inverse agonist of the histamine H 1 receptor. [68] It is a member of the ethanolamine class of antihistaminergic agents. [51] By reversing the effects of histamine on the capillaries, it can reduce the intensity of allergic symptoms.
Mirtazapine is a very strong H 1 receptor antagonist and, as a result, it can cause powerful sedative and hypnotic effects. [11] A single 15 mg dose of mirtazapine to healthy volunteers has been found to result in over 80% occupancy of the H 1 receptor and to induce intense sleepiness. [92]