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Valerian is the common name given to the crude drug consisting of the underground organs of the species Valeriana. Valeriana edulis ssp. procera Meyer is the Mexican valerian. The aim of the present work was to elucidate the neuropharmacological profile of a hydroalcohol extract of Valeriana edulis roots at doses of 100, 300 and 1000 mg/kg in several experimental models. A dose-dependent anticonvulsant and anxiolytic-like effect of V. edulis was demonstrated. In addition, the extract decreased rotarod performance and traction force and prolonged the pentobarbital-induced sleeping time at high doses. Concomitant administration of valerian extract and pentobarbital showed a synergistic effect on motor coordination and traction force in mice. The anxiolytic-like effect of V. edulis was compared with diazepam and with diphenhydramine and doxylamine, the latter in order to consider the H(1)-antihistamine effect as another possibility to explain, at least in part, the central nervous system depressant effect of valerian. These results also underlie the medical and industrial use of this species and allowed the conclusion that the extract of V. edulis has central nervous depressant properties similar to, but with some differences to V. of ficinalis, a very well known species.

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It has been declared frequently that valerian may potentiate the effect of other central nervous system (CNS) depressant drugs, however there has been a lack of experimental data. We have evaluated the profile of the interactions between the ethanol extract of Valeriana edulis spp procera and six CNS depressant drugs using an exploratory model to test the sedative effect in mice. All the compounds tested showed a dose-dependent sedative effect with the following ED50 values: valerian 181.62, diazepam 1.21, ethanol 1938, pentobarbital 11.86, buspirone 1.04, haloperidol 0.41 and diphenhydramine 17.06 mg kg-1. An isobolographic analysis was used to evaluate the sedative interaction of the intraperitoneal co-administration of 1:1 fixed-ratio combination of equi-effective doses of valerian extract with each CNS depressant drug. The ED50 theoretical (Zadd) and experimental (Zexp) for each combination were: valerian+diazepam,Zadd=91.41 mg kg-1, Zexp=81.64 mg kg-1; valerian+ethanol, Zadd=1060.22 mg kg-1, Zexp=687.89 mg kg-1; valerian+pentobarbital, Zadd=96.74 mg kg-1, Zexp=151.83 mg kg-1; valerian+buspirone, Zadd=91.33 mg kg-1, Zexp=112.73 mg kg-1; valerian+haloperidol, Zadd=91.01 mg kg-1, Zexp=91.52 mg kg-1; valerian+diphenhydramine, Zadd=99.34 mg kg-1, Zexp=123.52 mg kg-1. Neither synergistic nor attenuate effects were found in any of the combinations evaluated. We concluded that the valerian extract did not potentiate the sedative effect of commonly prescribed CNS depressant drugs as was expected. The additive effect found through the isobolographic analysis suggested that the sedative effect of V. edulis resulted from the activation of common mechanisms of haloperidol, diazepam, buspirone, pentobarbital, diphenhydramine and ethanol.

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