Study of the the anxiolytic effects of fennel and possible roles of both gabaergic system and estrogen receptors in these effects in adult female rat

Fennel is rich in phytoestrogens and is used for estrogen deficiency disorders. Estrogens affect anxiety through neurochemical systems such as GABA-A receptors. In this study the effects of fennel on GABA-A and estrogen receptors in anxiety were investigated. Adult female Wistar rats weighing (180±20 g) were divided into 8 groups. Groups received saline, fennel (200, 500, 750 mg/kg), tamoxifen (15 mg/kg) + fennel (500 mg/kg), picrotoxin (1 mg/kg) + fennel (500 mg/kg). A control group was also used. Elevated plus maze was used for evaluation of anxiety by measuring the time spent in the open arm. All drugs were administered intraperitoneally. The results showed that fennel only at the dose of 500 mg/kg had significant anxiolytic effects and increased the time spent in open arms (P<0.01). Picrotoxin (GABA-A antagonist) significantly prevented anxiolytic effect of 500 mg/kg of fennel (P<0.001). Tamoxifen, an estrogen receptor antagonist, also abolished the anxiolytic effect of fennel (P<0.001). Fennel reduced anxiety in rats and picrotoxin, a non-competitive antagonist of GABA-A receptors, as well as tamoxifen, an antagonist/agonist of estrogen receptors, reduced this anxiolytic effect. Thus fennel as a herbal drug seems to have an anxiolytic effect and it probably acts through GABA-A and estrogen receptors.