Inhibitory histamine H3-receptors on cholinergic nerves in human airways

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