Involvement of 5-HT1A in the anxiolytic-like effect of dichloromethane fraction of Pimenta pseudocaryophyllus

Anxiolytic-like effect and the mechanisms of actions involved in the dichloromethane fraction obtained from Pimenta pseudocaryophyllus coupled with qualitative and quantitative. Medicinal applications of Pimenta pseudocaryophyllus infusion as a diuretic and aphrodisiac agent as well as tranquilizer in the form of tea for the treatment of emotional tension in Brazilian folk medicine has been in practice since time immemorial. Despite its popular therapeutic acceptance and claims, there are scanty scientific reports to corroborate its central biological activities. To characterize anxiolytic-like effect of the dichloromethane fraction (DF) obtained from ethanolic leaf extract of the Pimenta pseudocaryophyllus and identify mechanisms of action involved while seeking to support its popular use as a soothing agent. Mice (25–35g) were treated orally with DF obtained from ethanolic leaf extract of Pimenta pseudocaryophyllus and were submitted to light-dark box (LDB) and elevated plus maze (EPM) tests. Different groups of mice were treated with flumazenil and NAN-190 to identify mechanisms of action involved in the anxiolytic-like effect of DF. Treatment with DF increased number of transitions and time spent in the light compartment of the LDB while the time spent and numbers of entries in the open arm of the LCE were significantly increased. Pre-treatment of the animal with flumazenil (2mg/kg, i.p. – competitive antagonist of benzodiazepine site of GABAA receptor) did not block this effect, thereby excluding participation of benzodiazepine site of the GABAA receptor. However, anxiolytic-like effect of DF was reversed by pre-treatment with NAN-190 (0.5mg/kg, i.p. – an antagonist of the 5-HT1A receptor) thereby suggesting involvement of 5-HT1A receptor. The thin layer chromatography and high-performance liquid chromatography analysis indicated the predominance of (E)-methyl isoeugenol and oleanolic acid in DF. These results support the popular use of Pimenta pseudocaryophyllus as a calming agent and suggest the involvement of 5-HT1A receptor.