Abstract
Cinnamon is a spice used by some populations as a traditional remedy to control blood pressure and thus hypertension. Cinnamon extract decreases contractility in some smooth muscles, but its effect on uterine smooth muscle is unknown. The aim of this study was to determine the physiological and pharmacological effects of cinnamon extract (CE) on the contractions of isolated rat uterine strips and to investigate its possible mechanism of action. Isolated longitudinal uterine strips were dissected from non-pregnant rats, mounted vertically in an organ bath chamber, and exposed to different concentrations of CE (10-20 mg/mL). The effect of CE was investigated in the presence of each of the following solutions: 60 mM KCl, 5 nM oxytocin, and 1 mu M Bay K8644. CE significantly decreased the force of uterine contraction in a concentration-dependent manner and significantly attenuated the uterine contractions elicited by KCl and oxytocin. In addition, CE significantly decreased the contractile force elicited when L-type Ca2+ channels were activated by Bay K8644. CE's major mechanism may be inhibition of L-type Ca2+ channels, which limits calcium influx. These data demonstrate that CE can be a potent tocolytic that can decrease uterine activity regardless of how the force was produced, even when the uterus was stimulated by agonists. As a result, cinnamon may be used to alleviate menstrual pain associated with dysmenorrhoea or prevent unwanted uterine activity in early pregnancy. (C) 2015 Society for Biology of Reproduction & the Institute of Animal Reproduction and Food Research of Polish Academy of Sciences in Olsztyn. Published by Elsevier Sp. z o.o. All rights reserved.