The antidepressant-like effects of Aloysia polystachya (Griseb.) Moldenke (Verbenaceae) in mice

Abstract

The aim of the present work is to evaluate the putative antidepressant-like effects of a hydro-ethanolic extract (CEAp) and their fractions from the aerial parts of Aloysia polystachya (Griseb.) Moldenke (Verbenaceac) on the performance of male mice in the forced swimming test (FST). A single dose (100.0 mg/kg p.o.) of CEAp, in male mice provoked a significant reduction of the immobility time (p < 0.01). Such effect was also observed with short-term treatment (7 days) with single doses of 1.0 (p < 0.01), 10.0 (p < 0.05) and 100.0 (p<0.05)mg/kg/day of CEAp. Additionally, in a different set of experiments, repeated administration in a 24-h period (24, 18 and I h before swimming test) with doses of 1.0 (p < 0.05) and 10.0 (p < 0.05) mg/kg p.o., of CEAp and 10.0 mg/kg p.o., (p < 0.05) of ethyl acetate fraction, provoked significant reduction of the immobility time of male mice in the FST. Moreover, it was noted important differences in the onset of the antidepressant-like effect in the FST, depending on the modality of treatment with CEAp (acute, short-term or repeated). Both, efficacy and potency were higher when repeated administration of CEAp was used, and surprisingly the dose of 10 mg/kg (24, 18 and I h before swimming test) was more effective than imipramine. In the same way, the short term administration (7 days) improved significantly efficacy and potency of the CEAp in comparison to a single dose treatment. The ethyl acetate fraction submitted to TLC demonstrated that main and minor components are phenolics and terpenes, respectively. In addition, this fraction gives a negative Shinoda's test for flavonoids. These results indicate an antidepressant-like profile of action for the hydro-ethanolic extract and the component(s) of the ethyl acetate fraction obtained from A. polystachya, which deserve further investigation.