Synergistic potentiation of anti-anxiety activity of valerian and alprazolam by liquorice.

Sir,

Anxiety is a common psychological and physiological state characterized by cognitive, somatic, emotional, and behavioral components, affecting 15.7 million people in US each year.[12] Valerian (Valeriana officinalis L.) has been historically popular as an anxiolytic and sedative andused as self-medication for sleeping problems.[3] It has been demonstrated that (Glycyrrhizin glabra) that if magnesium salts are administered along with saponin of liquoricehypnosis occurs.[4] This study evaluates the probable role of liquoricein potentiating anti-anxiety activity of valerian and alprazolam using elevated plus mazemodel.

The dried samples of valerian and liquoricewere obtained from LVG, Gandhi Bazaar,Ahmedabad (India). The materials were authenticated using morphological, microscopical and physicochemical parameters. Alprazolam tablet (B. No: 1390, Mfg. Date: Aug.2006, Exp. Date: July 2009), Unison Pharmaceuticals Ltd., Ahmedabad was purchased from the market. All the chemicals and reagents used for the studies were of analytical grade.

The crude materials were groundto 40 meshessieve and macerated with five times volume of ethanol:Water (7:3) for 24 h. The extracts were pooled, dried under vacuum and stored in air tight glass bottles.

Adult male Swiss albino mice (20-30 g) were housed in groups in polypropylene cages (11 × 17 × 28 cm) with wood shavings as bedding, under controlled conditions of light (12 h light-dark cycle) and temperature (25 ± 2°C). The animals had free access to water and food except 1 h before and during the experiments. The animals were allowed to acclimatize to laboratory conditions for 10 days before conducting the study. The experimental protocol wasapproved by the Institute Animal Ethics Committee (IAEC)and the experiments were carried out in accordance with theguidelines of CPCSEA on animal experimentation (Approval no. KBIPER/08/107).

Liquorice and valerian extracts(25 and 50 mg/kg, suspended in distilled water with 1% sodium CMC), or alprazolam (0.7 and 1.4 mg/kg; suspended in distilled water with 1% sodium CMC) were administered orally to mice by gavage. All the doses were prepared immediately before use. Control group was administered with the corresponding vehicle (1% sodium CMC in distilled water).

The plus-maze for mice consisted of two perpendicular open arms (30 × 5 cm) and two perpendicular closed arms (30 × 5 × 25 cm). The maze was 45 cm above the floor. One hour after oral treatment, the mouse were placed at the center of the plus-maze facing one closed arm and was observed for 20 min for number of entries in the open and closed arms and time spent in the open arms. A mouse was considered to have entered an arm when all four legs were on the arm. The percentage of time spent and percentage of entries on the open arms was considered as the anxiety index.[5]

Data obtained from elevated plus maze test were statistically analyzed using oneway ANOVA, followed by Dunnett test for comparison between various treatment groups. P < 0.05 was considered as a significant level. All data are expressed as mean ± S.D. (n = 6).

After oral administration of valerian extract to mice at 50 mg/kg and 25 mg/kg b.w., the time spent in the open arms and the percentage of number of entries in the open arms were significantly increased as compared to the vehicle-treated mice (P < 0.5). The Liquorice extract, when administered to mice at 25 and 50 mg/kg b.w., did not produce any significant behavioral change in the mice as compared to the vehicle-treated mice. Alprazolam, when administered at 1.4 mg/kg and 0.7 mg/kg b.w. to mice, showed a very significant increase (P < 0.5) in the percentage of number of entries in the open arms and time spent in the open arms [Figure 1].

Figure 1

Effect of Liquorice extract on anti-anxiety activity of Valerian extract and alprazolam in the elevated plus maze model (a) Time spent in open arms, (b) Time spent in closed arms, (c) number of entries in open arms, (d) number of entries in close arms. Data are presented as mean ±S.D. from a group of six mice. Doses are expressed as mg/ kg b.w. Val – Valerian extract, Gly – Liquorice extract, Alp – Alprazolam

The valerian extract (25 mg/kg b.w.), when administered orally to mice along with 25 mg/kg b.w. of liquorice extract, produced a significant increase in the percentage number of entries in the open arms andtime spent in open armsas compared to effects of valerian extract administered alone. Similar results were obtained when alprazolam was administered at 0.7 mg/kg b.w. along with liquorices extract (25 mg/kg b.w.). Thus, liquorice extract, at a therapeutically inactive dose, was found to potentiate the anti-anxiety activity of valerian and alprazolam.

The results obtained in the present study support the hypothesis that liquorice potentiates the activity of anti-anxiety drugs. The mechanism of potentiation of anti-anxiety activity by liquorice needs to be elucidated. The possible mechanism of potentiation of activity could be an increase in blood-brain barrier permeability of the drug by the constituents of liquorice, or an increase in the bioavailability of the drug due to increased absorption through gastro-intestinal tract or competitive inhibition of the metabolizing enzymes by the constituents of liquorice.