Influence of propofol and dexmedetomidine on oxytocin-induced contractions of isolated pregnant rat myometrium.

BACKGROUND:
Propofol is used after extraction of the fetus in pregnant women who have received combined spinal-epidural anesthesia for caesarean section. In previous studies, it was  shown that propofol has an inhibitory effect on uterine contraction like volatile anesthesia1、2). On the other hand, it has been shown that dexmedetomidine is an α2-adrenergic agonist that induced uterine contraction via a pathway involving G protein３）. However, there are no data on a comparison of the effects of propofol and dexmedetomidine on oxytocin-induced contractions of the isolated pregnant rat myometrium. The aim of this study was to determine the effects of propofol and dexmedetomidine on oxytocin-induced contractions of the isolated pregnant rat myometrium.

METHODS:
With institutional approval, 6-mm-long uterine rings were sliced from the uterine horns of late-term pregnant Wistar rats and mounted in a temperature-controlled organ bath containing 10 ml Krebs solution. After administration of oxytocin (20 nM), contraction and frequency changes in response to propofol (10-7-10-5M) or dexmedetomidine (10-9-10-7M) were evaluated. Statistical analysis was performed using the Kruskal-Wallis’ H-test followed by the Newman-Keuls-type test for multiple comparisons. P values < 0.05 were considered statistically significant.

RESULTS:
Propofol inhibited oxytocin-induced contraction of the pregnant rat myometrium in a dose-dependent manner, but dexmedetomidine did not inhibit oxytocin-induced contraction of the pregnant rat myometrium (figure). The effects of both propofol and dexmedetomidine on frequency did not change significantly. 


CONCLUSIONS:
Dexmedetomidine did not inhibit oxytocin-induced contraction of the pregnant rat myometrium. Dexmedetomidine may be preferable for maintaining uterine contraction in caesarean section.

REFERENCES
1) Anesthesiology 2001;95:1245-55
2) Acta Anaesthesiol Scand 2005;49:1355-1359
3) European Journal of pharmacylogy 2000;390:185-195