Inhibitory histamine H₃-receptors on cholinergic nerves in human airways

The histamine H₃-agonist, (R)-α-methylhistamine (α-MeHA) caused a dose-dependent inhibition of cholinergic contractile responses to electrical field stimulation in human bronchi without affecting the basal tone. α-MeHA, but, did not alter the response to acetylcholine. Blockade of H₁- and H₂-receptors, or α- and β-adrenoceptors failed to prevent the inhibitory effect of α-MeHA, whereas the specific H₃-antagonist, thioperamide, was effective. Our results indicate that H₃-receptors modulate cholinergic neurotransmission in human airways.