Effects of stachys lavandufolia Vahl on the elevated plus-maze model of anxiety in mice   Rabbani M., Sajjadi S.E. and Zarei, H.R. Department of Pharmacology, School of Pharmacy & Pharmaceutical Sci., Isfahan University of Medical Sci., Isfahan, Iran.

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Among the families of Iranian plants, stachys lavandulifolia Vahl has been commonly used for the treatment of anxiety and insomnia. Despite the widespread use of S. lavandulifolia as an anxiolytic, there are no pharmacological data to support such an effect. In the current study we used an elevated plus-maze model of anxiety to test the anxiolytic effects of the plant extract. The sedative effect of the plant extract and its effect on ketamine-induced sleeping time were also studied.

Dried and powdered aerial parts of the plant (100g) were macerated with 500 ml of ethanol and water (8:2). The extract was concentrated in a rotating evaporator under reduced pressure to give a residue (13.6 g). The residue consisting a mixture of several substances, was then dissolved in normal saline for final suitable concentration. Male TO mice (25-30 g) were used in the elevated plus-maze study as described in details elsewhere (Hogg, 1996). The effects of various doses of plant extracts and diazepam (0.5 mg kg^-1) were compared, 30 min after the i.p. injection each compounds. The number of entries and the time spent in the open and closed arms were recorded during 5-min test period. Distribution of behaviour on the maze was calculated as percent total for both open arm entries and time spent on different maze sections for 5 min time period. Statistical analysis was performed using one-way ANOVA with post hoc Duncan's test or Student t-test. All data are expressed as mean ± S.E.M.

S. lavandulifolia at dose of 100 mg/kg significantly increased the percentage of the open arm entries (94%, P<0.05) and timespent on the open arms (81%, P<0.05). At doses lower than 100 mg kg^-1, the plant extract did not significantly increase the percentage of the open arm entries or the time. At 100 mg kg^-1 the plant extract significantly decreased the locomotor activity at each of the time intervals (Table 1):

Table 1: Effects of diazepam and S. lavandulifolia extract on spontaneous locomotor activity. (n=6, mean ± s.e.m, *P < 0.05 compared with vehicle-treated controls).

In control animals the righting reflex was lost after 118 ± 2 sec of ketamine injection. Injection of plant extract at 100 mg kg^-1 significantly decreased this time by 24%. The total sleep time induced by ketamine was also significantly prolonged (from 1680 ± 121 sec to 2151 ± 229) by 100 mg kg^-1 of the plant extract.

The behaviour observed using the plus-maze in the present study confirmed the anxiolytic activity of diazepam as reported previously. In a similar fashion to diazepam, the extract of S. lavandulifolia produced anxiolytic effects, however, unlike diazepam the sedative effects of S. lavandulifolia was less pronounced as was indicated by locomotor activity measurement and its effect on ketamine-induced sleeping time.

Hogg S. (1996) Pharmacol. Biochem. Behav.. 54, 21-30.