Acetylcholine produces contractions mediated by the cyclooxygenase pathway in arterial vessels in the Chilean frog (Calyptocephalella gayi)

Acetilcolina produz contrações mediadas pela via da ciclooxigenase em vasos arteriais da rã chileno (Calyptocephalella gayi)

Abstract

Previous studies performed in marine fish (I. conceptionis and G. laevifrons) showed that indomethacin blocked arterial contraction mediated by acetylcholine (ACh). The objective of this study was to determine if contraction induced by acetylcholine is mediated by the cyclooxygenase pathway in several arterial vessels in the Chilean frog Calyptocephalella gayi. Arteries from the pulmonary (PA), dorsal (DA), mesenteric (MA) and iliac (IA) regions were dissected from 6 adult specimens, and isometric tension studies were done using dose response curves (DRC) for ACh (10^-13 to 10^-3 M) in presence of a muscarinic antagonist (Atropine 10^-5 M) and an unspecific inhibitor of cyclooxygenases (Indomethacin, 10^-5M). All the studied arteries exhibited vasoconstriction mediated by ACh. This vasoconstriction was abolished in the presence of atropine in DA, MA and IA and attenuated in PA. Indomethacin abolished the vasoconstriction in MA and attenuated the response in PA, DA and IA. Similar to marine fish, C. gayi have an ACh-mediated vasoconstrictor pattern regulated by muscarinic receptors that activate a cyclooxygenase contraction pathway. These results suggest that the maintenance in vasoconstrictor mechanisms mediated by ACh→COX →vasoconstriction is conserved from fish to frogs.

Keywords:
frog; vascular reactivity; acetylcholine; atropine; indomethacin; cyclooxygenase