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(Accepted April 22, 1999)
Extracts of Valeriana officinalis have been used in folkloric medicine for its sedative, hypnotic, tranquilizer and anticonvulsant effects, and may interact with [gamma]-aminobutyric acid (GABA) and/or benzodiazepine sites. At low concentrations, valerian extracts enhance [^sup 3^H]flunitrazepam binding (EC^sub 50^ 4.13 × 10^sup -10^ mg/ml). However, this increased [^sub 3^H]flunitrazepam binding is replaced by an inhibition at higher concentrations (IC^sub 50^ of 4.82 × 10^sup -1^ mg/ml). These results are consistent with the presence of at least two different biological activities interacting with [^sup 3^H]flunitrazepam binding sites. Valerian extracts also potentiate K+ or veratridine-stimulated release of radioactivity from hippocampal slices preloaded with [^sup 3^H]GABA. Finally, inhibition of synapiosomal [^sup 3^H]GABA uptake by valerian extracts also displays a biphasic interaction with guvacine. The results confirm that valerian extracts have effects on GABA^sub A^ receptors, but can also interact at other presynaptic components of GABAergic neurons.
KEY WORDS: Valeriana; [^sup 3^H]flunitrazepam; [^sup 3^H]GABA uptake; [^sup 3^H]GABA release.
INTRODUCTION
Extracts of Valeriana officinaux are used in folkloric medicine for its sedative, hypnotic, tranquilizer, and anticonvulsant effects (1,2). The major compounds present are the essential oils, classified as valepotriates and sesquiterpenes (3). The valepotriates, didrovaltrate, valtrate, acevaltrate, and isovaltrate, are the most important chemical group, although they are chemically unstable (4). Valepotriates potentiate hexobarbital anesthesia, suppress aggressivity, have anticonvulsant effects against pentylenetetrazol and strychnine seizures, increase thiopental sleeping time, reduce motility and have dose-dependent sedative effects (5-8). It has also been shown that a mixture of valepotriates is effective in attenuating benzodiazepine withdrawal symptoms in rats (8) suggesting that valerian extracts have some of the therapeutic effects of benzodiazepines.
The sesquiterpenes reduce locomotion, and increase pentobarbital and hexobarbital sleeping time of mice (9). Some sesquiterpenes, specially valerenic acid, influence serotonin and noradrenaline levels (9). Valerenic acid plays an important role in the depressive action and calming effects of valerian extract preparations suggesting that it has specific properties as a central nervous depressant (9). Moreover, studies with humans reveal that valerian extracts reduced latency to fall asleep as effectively as small doses of benzodiazepines (10).
These biological activities are consistent with a possible potentiation of GAB Aergic transmission. Santos et al., (l 1-14) report that aqueous valerian extracts inhibit the uptake and induce the release of...