Valerian extract modulates the GABAA-action on its receptors

Valerian act at the central GABA system which mediates inhibitory actions. A modulation of the GABA induced chloride channels conductance (I_GABA) has been tested for different valerian extracts manufactured with either ethanol (C1), methanol (C2) or ethyl acetate (C3) to obtain extracts with different constituents, and in addition an ethyl acetate extract from C2 residue (C4) as well as the combination of C2 + C4 (C5). From anaesthetized female Xenopus laevis parts of the ovaries were removed. Follicel membranes from isolated oocytes were enzymatically digested with collagenase. Chloride channels conductance were studied 1 to 5 days after microinjection of approximately equimolar cRNA mixtures of α ₁-, β ₂- and γ _2S- subunits of the rat GABA_A receptors in a ratio 1:1:10. Experiments were carried out at room temperature in bath solution containing (mM): 90 NaCl, 1 KCl, 1 MgCl2, 5 Hepes, 1CaCl2, adjusted to pH 7.4 with NaOH. Ionic influx was measured by means of the conventional two-microelectrode-voltage-clamp technique using a Turbo Tec 01C Amplifier (NPI Electronic, Germany). Voltage-recording and current-injecting microelectrodes were filled with 2 M KCl and had a resistance of 1–5 MΩ. GABA was solved freshly in bath solution every day immediately before the experiments. Valerian extracts (C1– C5) were solved in DMSO (20mg/mL) and the stock solution diluted to 50µg/mL and 100µg/mL, respectively. The extracts were either co-applied with GABA (EC_3–10) or applied alone. Almost no stimulatory effects were observed if the extracts were applied alone. An enhancement of I_GABA (EC_3–10) of 134% and 123% respectively, could be observed for extracts C3 and C4. The following order of the activity was obtained: C4=C3 > C1=C5 > C2, indicating that the different active components by the solvents used are distinguishable solved.