H1-receptor

Histamine receptor H1
3RZE)
Available structures
PDB Ortholog search: RCSB
Identifiers
HRH1 Gene
RNA expression pattern

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. The H1 receptor is linked to an intracellular G-protein (Gq) that activates phospholipase C and the phosphatidylinositol (PIP2) signaling pathway. Antihistamines, which act on this receptor, are used as anti-allergy drugs. The crystal structure of the receptor has been determined (shown on the right).[1]

Role in inflammation

The production of prostaglandin E2 synthase induces the release of histamine from neurons, causing systemic vasodilation, along with increased cell permeability due to its action on H1 receptors.

Neurophysiology

Histamine H1 receptors are activated by endogenous histamine, which is released by neurons that have their cell bodies in the tuberomammillary nucleus of the hypothalamus. The histaminergic neurons of the tuberomammillary nucleus become active during the 'wake' cycle, firing at approximately 2 Hz; during slow wave sleep, this firing rate drops to approximately 0.5 Hz. Finally, during REM sleep, histaminergic neurons stop firing altogether. It has been reported that histaminergic neurons have the most wake-selective firing pattern of all known neuronal types.[2]

In the cortex, activation of H1 receptors leads to inhibition of cell membrane potassium channels. This depolarizes the neurons and increases the resistance of the neuronal cell membrane, bringing the cell closer to its firing threshold and increasing the excitatory voltage produced by a given excitatory current. H1 receptor antagonists, or antihistamines, produce drowsiness because they oppose this action, reducing neuronal excitation.[3]

See also

References

Further reading

External links