Valerenic acid, actein an derivates

Extrakte von Baldrian (Valeriana officinalis) und Traubensilberkerze (Actaea racemosa) finden Anwendung als „Phytopharmaka“. Ihre Wirkmechanismen sind unbekannt. In der vorliegenden Arbeit konnte gezeigt werden, dass sowohl Baldrian- als auch Traubersilberkerzen-Extrakte eine deutliche Stimulation von Chloridströmen (IGABA) durch GABA Rezeptoren induzierten. Valerensäure (VA), ein wichtiger Inhaltsstoff des Baldrians, wurde als Untereinheiten-spezifischer Modulator von GABAA Rezeptoren identifiziert, da ausschließlich 2/3 Untereinheiten inkorporierende Rezeptoren positiv moduliert wurden. Das Einführen der Punktmutation 2N265S (welche die Modulation von GABAA Rezeptoren durch Loreclezol hemmt) reduzierte die Modulation der Rezeptoren durch VA. VA zeigte außerdem eine geringere Effizienz an 422S GABAA Kanälen. In höheren Konzentrationen (≥100 M) blockierten VA und Acetoxy-VA IGABA über einen “open-channel-block” Mechanismus. Zusammengefasst wurde VA als Untereinheiten-spezifischer Modulator von GABAA Rezeptoren identifiziert, der möglicherweise mit der Loreclezol-Bindungsstelle interagiert. Actein, ein Inhaltsstoff der Traubensilberkerze, wurde als effizienter Modulator von GABAA Rezeptoren identifiziert, wobei die stärkste Potenzierung von IGABA an 11 Rezeptoren beobachtet (2169.4±374.5%) wurde, während der Effekt an 52 Rezeptoren deutlich schwächer ausgeprägt war (225.8±44.8%). Actein (6 mg/kg) reduzierte signifikant die spontane Motoraktivität der Mäuse im Open Field Test. Im Light/Dark Choice Test, verbrachten Actein-behandelte Mäuse im Vergleich mit Kontrolltieren signfikant mehr Zeit im hellbeleuchten Teil der Box. Eine deutliche Reduktion von ΔT (Differenz der Körpertemperatur vor und nach Actein-Injektion; 6 and 20 mg/kg Actein) wurde im Stress-induced Hyperthermia Test beobachtet. Diese Daten legen nahe, dass Actein in vivo über eine Interaktion mit GABAA Rezeptoren sedative und anxiolytische Wirkungen induzieren kann und dass diese Effekte möglicherweise zur beobachteten Linderung postmenopausaler Beschwerden beitragen.Valerian and Actaea racemosa extracts are commonly used as “herbal medicinal products”, while their mechanisms of action are largely unknown. In this study, I have demonstrated that Valerian and Actaea racemosa extracts at a concentration of 100 g/ml enhance chloride currents through GABAA receptors (IGABA). Valerenic acid (VA) selectively enhances IGABA through receptors incorporating 2 or 3 subunits and its effect is not -subunit dependent. The stimulatory effect of VA on 12 receptors was substantially reduced by the point mutation 2N265S (known to inhibit loreclezole action). VA displayed a significantly lower efficiency on channels incorporating 4 subunits (422S receptors). At high concentrations (≥ 100 M) VA and acetoxy-VA inhibit IGABA suggesting an open-channel block. In summary, VA was identified as a subunit-specific allosteric modulator of GABAA receptors that is likely to interact with the loreclezole binding pocket. Actein (a compound isolated from Actaea racemosa) was identified as an efficient modulator of GABAA receptors displaying the strongest effect on 11 receptors (2169.4±374.5%), whereas on 52 containing receptors a substantially weaker efficiency was observed (225.8±44.8%). Actein (6 mg/kg) significantly decreased the spontaneous motor activity of mice in the open field test. A significant decrease of ΔT (difference of basal temperature before and after actein injection; 6 and 20 mg/kg actein) was observed in the stress-induced hyperthermia test. These in vivo data suggest that sedative and anxiolytic properties of actein may contributes to the treatment of postmenopausal disorders with Actaea racemosa extract

Self-Administration of Entactogen Psychostimulants Dysregulates Gamma-Aminobutyric Acid (GABA) and Kappa Opioid Receptor Signaling in the Central Nucleus of the Amygdala of Female Wistar Rats

Male rats escalate intravenous self-administration of entactogen psychostimulants, 3,4-methylenedioxymethcathinone (methylone) and 3,4-methylenedioxymethamphetamine (MDMA) under extended access conditions, as with typical psychostimulants. Here, we investigated whether female rats escalate self-administration of methylone, 3,4-methylenedioxypentedrone (pentylone), and MDMA and then studied consequences of MDMA and pentylone self-administration on GABAA receptor and kappa opioid receptor (KOR) signaling in the central nucleus of the amygdala (CeA), a brain area critically dysregulated by extended access self-administration of alcohol or cocaine. Adult female Wistar rats were trained to self-administer methylone, pentylone, MDMA (0.5 mg/kg/infusion), or saline-vehicle using a fixed-ratio 1 response contingency in 6-h sessions (long-access: LgA) followed by progressive ratio (PR) dose-response testing. The effects of pentylone-LgA, MDMA-LgA and saline on basal GABAergic transmission (miniature post-synaptic inhibitory currents, mIPSCs) and the modulatory role of KOR at CeA GABAergic synapses were determined in acute brain slices using whole-cell patch-clamp. Methylone-LgA and pentylone-LgA rats similarly escalated their drug intake (both obtained more infusions compared to MDMA-LgA rats), however, pentylone-LgA rats reached higher breakpoints in PR tests. At the cellular level, baseline CeA GABA transmission was markedly elevated in pentylone-LgA and MDMA-LgA rats compared to saline-vehicle. Specifically, pentylone-LgA was associated with increased CeA mIPSC frequency (GABA release) and amplitude (post-synaptic GABAA receptor function), while mIPSC amplitudes (but not frequency) was larger in MDMA-LgA rats compared to saline rats. In addition, pentylone-LgA and MDMA-LgA profoundly disrupted CeA KOR signaling such as both KOR agonism (1 mM U50488) and KOR antagonism (200 nM nor-binaltorphimine) decreased mIPSC frequency suggesting recruitment of non-canonical KOR signaling pathways. This study confirms escalated self-administration of entactogen psychostimulants under LgA conditions in female rats which is accompanied by increased CeA GABAergic inhibition and altered KOR signaling. Collectively, our study suggests that CeA GABA and KOR mechanisms play a critical role in entactogen self-administration like those observed with escalation of alcohol or cocaine self-administration

Bioactivity-guided isolation of GABA(A) receptor modulating constituents from the rhizomes of Actaea racemosa

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GABAA receptor modulation by piperine and a non-TRPV1 activating derivative

AbstractThe action of piperine (the pungent component of pepper) and its derivative SCT-66 ((2E,4E)-5-(1,3-benzodioxol-5-yl))-N,N-diisobutyl-2,4-pentadienamide) on different gamma-aminobutyric acid (GABA) type A (GABAA) receptors, transient-receptor-potential-vanilloid-1 (TRPV1) receptors and behavioural effects were investigated.GABAA receptor subtypes and TRPV1 receptors were expressed in Xenopus laevis oocytes. Modulation of GABA-induced chloride currents (IGABA) by piperine and SCT-66 and activation of TRPV1 was studied using the two-microelectrode-voltage-clamp technique and fast perfusion. Their effects on explorative behaviour, thermoregulation and seizure threshold were analysed in mice. Piperine acted with similar potency on all GABAA receptor subtypes (EC50 range: 42.8±7.6μM (α2β2)–59.6±12.3μM (α3β2)). IGABA modulation by piperine did not require the presence of a γ2S-subunit, suggesting a binding site involving only α and β subunits. IGABA activation was slightly more efficacious on receptors formed from β2/3 subunits (maximal IGABA stimulation through α1β3 receptors: 332±64% and α1β2: 271±36% vs. α1β1: 171±22%, p<0.05) and α3-subunits (α3β2: 375±51% vs. α5β2:136±22%, p<0.05). Replacing the piperidine ring by a N,N-diisobutyl residue (SCT-66) prevents interactions with TRPV1 and simultaneously increases the potency and efficiency of GABAA receptor modulation. SCT-66 displayed greater efficacy on GABAA receptors than piperine, with different subunit-dependence. Both compounds induced anxiolytic, anticonvulsant effects and reduced locomotor activity; however, SCT-66 induced stronger anxiolysis without decreasing body temperature and without the proconvulsive effects of TRPV1 activation and thus may serve as a scaffold for the development of novel GABAA receptor modulators

A cycloartane glycoside derived from actaea racemosa L. Modulates GABA(A) receptors and induces pronounced sedation in mice

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