Involvement of serotonergic system in anxiolytic effect of dichloromethane fraction of Pimenta pseudocaryophyllus (Gomes) Landrum

The purpose of this study was to verify the putative anxiolytic-like activity of dichloromethane fraction (DF) prepared from the leaves of Pimenta pseudocaryophyllus (Gomes) Landrum (Pp) and the mechanism of action involved using the elevated plus maze (EPM) and light dark box (LDB) tests. Male Swiss mice (25–35g) were treated orally with the vehicle (10mL/Kg), DF (125,250 and 500mg/kg p.o.) or positive controls diazepam (1mg/Kg) and buspirone (10mg/Kg) 1h before behavioral evaluation in the EPM and LDB. A treatment of DF significantly increased the percentage time spent and the number of entries into the open arms of the EPM as well as latency, number of transitions and time spent at the light part of the LDB in a dose dependent manner. The effects of DF in 250mg/kg were antagonized by the 5-HT1A receptor antagonist NAN-190 (0.5mg/kg i.p.). However, the effects could not be blocked by the benzodiazepine antagonist flumazenil (2mg/kg i.p.). These results indicate an effective anxiolytic activity of Pp mainly mediated via the Serotonergic system without compromising motor function of the mice. Although there is need for the isolation of the less polar constituent responsible for this effect, further clinical investigations are necessary for its possible application as an alternative for the treatment of anxiety disorders to other medications currently in use.

Keywords: Anxiolytic effect; Benzodiazepines, Elevated plus maze, light-Dark box, Pimenta pseudocaryophyllus, GABA receptor, 5-HT1A receptor

Acknowledgement: CNPq, CAPES, FAPEG, FUNAPE/UFG