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Background and Purpose: Prostamides are lipid mediators formed by COX-2-catalysed oxidation of the endocannabinoid anandamide and eliciting effects often opposed to those caused by anandamide. Prostamides may be formed when hydrolysis of anandamide by fatty acid amide hydrolase (FAAH) is physiologically, pathologically or pharmacologically decreased. Thus, therapeutic benefits of FAAH inhibitors might be attenuated by concomitant production of prostamide F2 α . This loss of benefit might be minimized by compounds designed to selectively antagonize prostamide receptors and also inhibiting FAAH., Experimental Approach: Inhibition of FAAH by a series of selective antagonists of prostamide receptors, including AGN 204396, AGN 211335 and AGN 211336, was assessed using rat, mouse and human FAAH in vitro, together with affinity for human recombinant CB1 and CB2 receptors. Effects in vivo were measured in a model of formalin-induced inflammatory pain in mice., Key Results: The prostamide F2 α receptor antagonists were active against mouse and rat FAAH in the low μM range and behaved as non-competitive and plasma membrane-permeant inhibitors. AGN 211335, the most potent inhibitor of rat FAAH (IC50  = 1.2 μM), raised exogenous anandamide levels in intact cells and also bound to cannabinoid CB1 receptors. Both AGN 211335 and AGN 211336 (0.25-1 mg·kg(-1) , i.p.) inhibited the formalin-induced nociceptive response in mice., Conclusions and Implications: Synthetic compounds with indirect agonist activity at cannabinoid receptors and antagonist activity at prostamide receptors can be developed. Such compounds could be used as alternatives to selective FAAH inhibitors to prevent the possibility of prostamide F2 α -induced inflammation and pain., Linked Articles: This article is part of a themed section on Cannabinoids 2013. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-6., (© 2013 The British Pharmacological Society.)

Background and Purpose: A prostamide analogue, bimatoprost, has been shown to be effective in reducing intraocular pressure, but its precise mechanism of action remains unclear. Hence, to elucidate the molecular mechanisms of this effect of bimatoprost, we focused on pharmacologically characterizing prostaglandin FP receptor (FP) and FP receptor variant (altFP) complexes., Experimental Approach: FP receptor mRNA variants were identified by reverse transcription-polymerase chain reaction. The FP-altFP4 heterodimers were established in HEK293/EBNA cells co-expressing FP and altFP4 receptor variants. A fluorometric imaging plate reader was used to study Ca2+ mobilization. Upregulation of cysteine-rich angiogenic protein 61 (Cyr61) mRNA was measured by Northern blot analysis, and phosphorylation of myosin light chain (MLC) by western analysis., Key Results: Six splicing variants of FP receptor mRNA were identified in human ocular tissues. Immunoprecipitation confirmed that the FP receptor is dimerized with altFP4 receptors in HEK293/EBNA cells co-expressing FP and altFP4 receptors. In the studies of the kinetic profile for Ca2+ mobilization, prostaglandin F2alpha (PGF2alpha) elicited a rapid increase in intracellular Ca2+ followed by a steady state phase. In contrast, bimatoprost elicited an immediate increase in intracellular Ca2+ followed by a second phase. The prostamide antagonist, AGN211335, selectively and dose-dependently inhibited the bimatoprost-initiated second phase of Ca2+ mobilization, Cyr61 mRNA upregulation and MLC phosphorylation, but did not block the action of PGF2alpha., Conclusion and Implications: Bimatoprost lacks effects on the FP receptor but may interact with the FP-altFP receptor heterodimer to induce alterations in second messenger signalling. Hence, FP-altFP complexes may represent the underlying basis of bimatoprost pharmacology.