Question

H12 and 3 receptors work by
what mechanism
​

Answer 1

There are four known histamine receptors:

H1 receptor

H2 receptor

H3 receptor

H4 receptor

Histamine receptors

Receptor Mechanism Function Antagonists

H1 Gq

ileum contraction

modulate circadian cycle

itching

systemic vasodilatation

bronchoconstriction (allergy-induced asthma)

H1-receptor antagonists

Diphenhydramine

Loratadine

Cetirizine

Fexofenadine

Clemastine

Rupatadine

H2 Gs

↑ cAMP2+

speed up sinus rhythm

Stimulation of gastric acid secretion

Smooth muscle relaxation

Inhibit antibody synthesis, T-cell proliferation and cytokine production

H2-receptor antagonists

Ranitidine

Cimetidine

Famotidine

Nizatidine

H3 Gi

Decrease Acetylcholine, Serotonin and Norepinephrine Neurotransmitter release in CNS

Presynaptic autoreceptors

H3-receptor antagonists

ABT-239

Ciproxifan

Clobenpropit

Thioperamide

H4 Gi

mediate mast cell chemotaxis.[2]

H4-receptor antagonists

Thioperamide

JNJ 777712

Answer 2

Answer:

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