A Lack of tolerance to the anxiolytic action of Echium amoenum

Abstract

The anxiolytic effect of the flower of Echium. amoenum was shown in several experimental studies in mice. The present study was aimed to determine whether tolerance develops to anxiolytic action of E. amoenum in mice. NMRI male mice were injected intraperitoneal with hydroalcoholic extract (12.5, 25 and 50 mg/kg) or saline once each day (8 am) for period of 7 days and then tested on light/dark box model. Anxiolytic effect was determined by light/dark box and elevated plus-maze. According to the results, hydroalcohoic extract of E. amoenum when given both acutely and chronically (7 days) at 25 and 50 mg/kg, significantly increased the time in the illuminated zone. The number of transitions in the light/dark apparatus, however, was not significantly altered by the tested doses of the plant. Diazepam at 0.5 and 1 mg/kg produced anxiolytic effect in both model of anxiety, namely, the light/dark box and elevated plus-maze. No tolerance was developed to the anxiolytic effect of E. amoenum extract after 7 days of treatment. Our results suggest that one week treatment with extract of the E. amoenum does not produce tolerance to its anxiolytic action. Longer period of treatment using implant procedure is probably necessary to cause molecular changes in order to induce tolerance.