RESUMEN
Increasing the ectopic uterine motility is the major reason for primary dysmenorrhea. This motility is the basis for several symptoms including for pain is the main complaints of patients with primary dysmenorrhea. There are several mechanisms, which initiate dysmenorrhea. Therefore, different compounds can be employed to control its symptoms. In long-term therapy, combination of oestrogens and progestins may be useful. In short-term therapy, dysmenorrhea sometimes non-steroidal anti-inflammatory drugs (NSAIDs) are used. Most of NSAIDs in long-term therapy show severe adverse effects. In an attempt to find agents with less adverse effect the fennel essential oil (FEO) was chosen for this investigation. In this article, effects of FEO on the uterine contraction and estimation of LD(50) in rat were described. For assessment of pharmacological effects on the isolated rat uterus, oxytocin (0.1, 1 and 10 mu/ml) and prostaglandin E(2) (PGE(2)) (5x10(-5) M) were employed to induce muscle contraction. Administration of different doses of FEO reduced the intensity of oxytocin and PGE(2) induced contractions significantly (25 and 50 microg/ml for oxytocin and 10 and 20 microg/ml PGE(2), respectively). FEO also reduced the frequency of contractions induced by PGE(2) but not with oxytocin. LD(50) of FEO was obtained in the female rats by using moving average method. The estimated LD(50) was 1326 mg/kg. No obvious damage was observed in the vital organs of the dead animals.