Viola tricolor Hydroalcoholic Extract Improves Behavioral Deficiencies in Rats Exposed to Chronic Immobilization Stress

HIGHLIGHTS

• V. tricolor ameliorates memory impairment caused by immobilization in rats.

• V. tricolor diminishes anxiety- and depression-like behaviors in immobilized rats.

• V. tricolor decreases chronic immobilization-induced neuronal loss in the hippocampus.

• V. tricolor reduces expression of IL-6 in the hippocampus of immobilized rats.

Abstract

This study aims to investigate the effect of Viola tricolor extract on hippocampal neuronal death, interleukin (IL) -6 and IL-10 expression, spatial memory, anxiety, and depression in rats exposed to chronic immobilization stress. Rats were divided into groups Control, Viola300, Viola600, Stress, Stress-Viola300, and Stress-Viola600. Animals were placed in a restrainer (6 h / 21 days) to stress exposure. V. tricolor hydro-alcoholic extract was also administrated at doses of 300 and 600 mg/kg by gavage. The extract caused immobilized animals to spend more time in the target quadrant in the Morris water maze test. It also increased the percentage of entries into the open arm and the percentage of time spent in the open arm of the elevated plus-maze in immobilized rats. Treatment with the V. tricolor extract significantly reduced the immobility time of stressed rats in the forced swimming test. Furthermore, it significantly reduced neuronal death and expression of IL-6 in the hippocampus of immobilized animals but could not prevent the decrease of IL-10 expression. We concluded that V. tricolor protects rats from stress-induced behavioral damages, at least in part, by suppressing neuronal death and decreasing IL-6 expression.

Keywords:
Viola tricolor; Memory; Anxiety; Interleukin-6