Anxiolytic effect of an extract of Salvia miltiorrhiza roots in rats

Background: Preparations from roots of Salvia miltiorrhiza, a herb widely used in traditional Chinese medicine, have been reported to induce a series of central effects, including sedation. In the wake of this ethnopharmacological information, the present study was designed to assess the anxiolytic potential of an extract of S miltiorrhiza roots. Methods: To this end, rats were acutely treated with S miltiorrhiza extract (0, 50, and 100 mg/kg; i.g.) and exposed to the Elevated Plus Maze (EPM) test. The effect of treatment with S miltiorrhiza extract on Stress-Induced Hyperthermia (SIH; a physiological response to stressful events) was also evaluated. Results: Treatment with 100 mg/kg S miltiorrhiza extract produced robust anxiolytic effects at the EPM test; specifically, it increased (a) percent of entries into open arms, (b) percent of time spent in open arms, (c) total number of head dips, (d) number of unprotected head dips, and (e) number of end-arm explorations in open arms, without any alteration in spontaneous locomotor activity. Treatment with 100 mg/kg S miltiorrhiza extract also suppressed SIH response. The anxiolytic effects produced by 100 mg/kg S miltiorrhiza extract were comparable to those exerted by acute treatment with 1.5 mg/kg (i.p.) of the reference compound, diazepam. Conclusion: These data demonstrate the ability of an extract of S miltiorrhiza roots to produce anxiolysis in two different rodent models of "anxiety".