Calcium‐dependent relaxant effect of carvacrol on gastric fundus smooth muscle

Abstract

Carvacrol is a monoterpene that relaxes smooth muscle on several tissues. It has been largely studied due its huge biomedical applications such as antioxidant, antibacterial, hepatoprotective, anti‐inflammatory, antispasmodic and gastroprotective. However, mechanisms involved in those pharmacological actions, specially that antispasmodic, are not well known. Thus, we aimed to evaluate the myorelaxant effect of carvacrol on the gastric fundus and its possible underlying mechanisms of action. We used male Wistar rats weighing between 150 and 350 g, kept at 22 °C, by day/night cycle, with water and food ad libitum. The rats were sacrificed after Thiopental Sodium 40 mg/kg anesthesy. Stomach was removed after laparothomy and placed in Tyrode's nutrient solution at 37°C under aeration with carbogen solution containing 95% O2 and 5% CO2. Thereafter, stomach was sectioned into longitudinal strips of length 1 cm in length each, which were individually suspended in glass chambers and stabilized for 60 minutes, when nutrient solution was changed every 15 minutes. Gastric tissues were previously contracted at different times by both 60 mM isotonic KCl (K60) or 1 μM carbachol (CCh). The inhibition of the submaximal contractile response induced by CCh or K60 was evaluated by comparing the responses before (control) and after by the addition of carvacrol in different concentrations (3 to 1000 μM) into the organs bath after a period of 10 minutes. To evaluate the role of extracellular calcium on the relaxant effects, tissue was pre‐incubated with carvacrol exposed to calcium‐free K60, and contracted by K60. Statistical analysis was performed by mean ± SEM of the measures, by two‐way ANOVA analyse with Bonferroni pos‐hoc test, with significance level p<0.05. Carvacrol relaxed gastric fundus previously contracted by CCh, a muscarinic agonist type M3 (1000 μM relaxed 46%, 600 μM relaxed 35% and 300 μM relaxed 22%). In the experiment performed with 60 mM KCl, the contractions were reduced in the proportions of 26%, 33%, 42%, 56%, and 70% at 30, 100, 300, 600 and 1000 μM, respectively.At the concentration of 1000 μM of carvacrol in medium at cumulative concentrations of Ca2+ in Ca2+‐free solution, the concentration 0.5 mM inhibited contraction in 61% (11.75 ± 112). However, at 1 mM concentration we had a contraction reduction of 86% (35.92 ± 136.2) and 2mM concentration inhibited the contraction in 71% (21.12 ± 121.4 μg/ml). Carvacrol relaxed 29% of the CCh‐induced contraction in the presence of nifedipine. In presence of TEA, a K+ channels inhibitor, it was possible to observe that carvacrol in the concentration 1000μM was able to induce the relaxation about 14% (−85,23 ± 6,755) in the contraction maintained by CCh. Carvacrol showed relaxant effect on gastric fundus, mainly by extracellular calcium blockage.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.