Mechanisms underlying tissue selectivity of anandamide and other vanilloid receptor agonists.
Anandamide acts as a full vanilloid receptor agonist in many bioassay systems, but it is a weak activator of primary afferents in the airways. To address this discrepancy, we compared the effect of different vanilloid receptor agonists in isolated airways and mesenteric arteries of guinea pig using preparations containing different phenotypes of the capsaicin-sensitive sensory nerve. We found that anandamide is a powerful vasodilator of mesenteric arteries but a weak constrictor of main bronchi. These effects of anandamide are mediated by vanilloid receptors on primary afferents and do not involve cannabinoid receptors. Anandamide also contracts isolated lung strips, an effect caused by the hydrolysis of anandamide and subsequent formation of cyclooxygenase products. Although capsaicin is equally potent in bronchi and mesenteric arteries, anandamide, resiniferatoxin, and particularly olvanil are significantly less potent in bronchi. Competition experiments with the vanilloid receptor antagonist capsazepine did not provide evidence of vanilloid receptor heterogeneity. Arachidonoyl-5-methoxytryptamine (VDM13), an inhibitor of the anandamide membrane transporter, attenuates responses to olvanil and anandamide, but not capsaicin and resiniferatoxin, in mesenteric arteries. VDM13 did not affect responses to these agonists in bronchi, suggesting that the anandamide membrane transporter is absent in this phenotype of the sensory nerve. Computer simulations using an operational model of agonism were consistent, with differences in intrinsic efficacy and receptor content being responsible for the remaining differences in agonist potency between the tissues. This study describes differences between vanilloid receptor agonists regarding tissue selectivity and provides a conceptual framework for developing tissue-selective vanilloid receptor agonists devoid of bronchoconstrictor activity.
Department of Clinical Pharmacology, Institute of Laboratory Medicine, Lund University Hospital, Lund University, Lund, Sweden.
David A
DA
Andersson
Mikael
M
Adner
Edward D
ED
Högestätt
Peter M
PM
Zygmunt
D000818:Animals; D001095:Arachidonic Acids / Q000494:pharmacology*; D001980:Bronchi / Q000187:drug effects* / Q000378:metabolism; D001981:Bronchial Arteries / Q000187:drug effects / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002211:Capsaicin / Q000031:analogs & derivatives* / Q000494:pharmacology; D003198:Computer Simulation; D063388:Endocannabinoids; D006168:Guinea Pigs; D008168:Lung / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects* / Q000378:metabolism; D053284:Polyunsaturated Alkamides; D011955:Receptors, Drug / Q000819:agonists* / Q000037:antagonists & inhibitors
D001095:Arachidonic Acids; D002121:Calcium Channel Blockers; D063388:Endocannabinoids; D053284:Polyunsaturated Alkamides; D011955:Receptors, Drug; C071423:capsazepine; D002211:Capsaicin; C078814:anandamide