What is the Difference Between H1 and H2 Receptors?

Histamine receptors are rhodopsin-like G protein-coupled receptors that mediate the action of histamine in various physiological processes, including allergic reactions. There are four histamine receptors, with H1 and H2 receptors being the most widely studied. The main differences between H1 and H2 receptors are their mechanisms and functions.

1. H1 Receptors:

• Drive cellular migration, nociception (pain), vasodilation, and bronchoconstriction.
• Couple with Gq/11 to stimulate phospholipase C.
• Responsible for the vasoconstrictor and minimal cardiac depressant actions of histamine.
• H1-receptor antagonists, also known as H1 antihistamines, are used to treat allergy symptoms.

1. H2 Receptors:

• Modify gastric acid secretion, airway mucus production, and vascular permeability.
• Interact with Gs to activate adenylyl cyclase.
• Mediate vasodilation, tachycardia, and increased cardiac output induced by histamine.
• H2-receptor antagonists, also known as H2 blockers, mainly affect the stomach and were discovered later than H1 blockers.

In summary, H1 receptors are mainly involved in allergy-related responses and are targeted by H1 antihistamines, while H2 receptors modulate gastric acid secretion, airway mucus production, and vascular permeability, and are targeted by H2 blockers.

Comparative Table: H1 vs H2 Receptors

H1 and H2 receptors are rhodopsin-like G protein-coupled receptors that mediate the action of histamine in various physiological reactions, including allergic responses. The key difference between H1 and H2 receptors lies in their mechanism of action. Here is a table summarizing their differences:

Both H1 and H2 receptors play crucial roles in histamine-mediated responses, but they have distinct functions and mechanisms of action.