Role of GABAergic antagonism in the neuroprotective effects of bilobalide

Vinylcyclopropane [3+2] Cycloaddition with Acetylenic Sulfones Based on Visible Light Photocatalysis

The first intermolecular visible light [3+2] cycloaddition reaction performed on a meta photocycloadduct employing acetylenic sulfones is described. The developed methodology exploits the advantages of combining UV and visible-light in a two-step sequence that provides a photogenerated cyclopropane which, through a strain-release process, generates a new cyclopentane ring while significantly increasing the molecular complexity. Mechanistic studies and DFT calculations indicate an energy transfer pathway for the visible light-driven reaction step. This strategy could be extended to simpler vinylcyclopropanes.

Advantages of Short-term Personalized Vestibular Rehabilitation at Home Guided by Professional Therapist for Treatment of Decompensated Vestibular Vertigo

OBJECTIVE

Patients suffered a lot from decompensated vestibular vertigo. Pharmacotherapy and vestibular rehabilitation training have been proven to be effective in prompting vestibular compensation. Routine rehabilitation training is faced with the challenges of patients' compliance, completion, the average recuperation time and so on. This study is aimed to investigate advantages of short-term personalized vestibular rehabihitation at home guided by professional therapist.

METHODS

A short-term personalized vestibular rehabilitation program (ST-PVR) was designed for patients with decompensated vestibular vertigo in this study.

RESULTS

Patients experiencing the ST-PVR program showed significant improvement of Self-Rating Anxiety Scale (SAS), Dizziness Handicap Inventory (DHI), Activities-Specific Balance Confidence Scale (ABC) scores by the second follow-up (at 2nd week after treatment, P<0.05). However-improvement in the medication group occurred slightly later, DHI for 1 month and SAS for 2 months after treatment (P<0.05). Also, the improvement in the onset time of unilateral weakness (UW) at 2nd week after treatment in the personalized vestibular rehabilitation (PVR) group was faster than that in the medication group.

CONCLUSION

In general, the short-term PVR program showed great advantages by prompting vestibular compensation quickly and putting forward future direction for clinical treatment on decompensated vestibular vertigo.

Sesquiterpenes and sesquiterpenoids harbor modulatory allosteric potential and affect inhibitory GABAA receptor function in vitro

Naturally occurring compounds such as sesquiterpenes and sesquiterpenoids (SQTs) have been shown to modulate GABA_A receptors (GABA_A Rs). In this study, the modulatory potential of 11 SQTs at GABA_A Rs was analyzed to characterize their potential neurotropic activity. Transfected HEK293 cells and primary hippocampal neurons were functionally investigated using electrophysiological whole-cell recordings. Significantly different effects of β-caryophyllene and α-humulene, as well as their respective derivatives β-caryolanol and humulol, were observed in the HEK293 cell system. In neurons, the concomitant presence of phasic and tonic GABA_A R configurations accounts for differences in receptor modulation by SQTs. The in vivo presence of the γ₂ and δ subunits is important for SQT modulation. While phasic GABA_A receptors in hippocampal neurons exhibited significantly altered GABA-evoked current amplitudes in the presence of humulol and guaiol, negative allosteric potential at recombinantly expressed α₁ β₂ γ₂ receptors was only verified for humolol. Modeling and docking studies provided support for the binding of SQTs to the neurosteroid-binding site of the GABA_A R localized between transmembrane segments 1 and 3 at the (⁺ α)-(^- α) interface. In sum, differences in the modulation of GABA_A R isoforms between SQTs were identified. Another finding is that our results provide an indication that nutritional digestion affects the neurotropic potential of natural compounds.

All-carbon [3 + 2] cycloaddition in natural product synthesis

Many natural products possess interesting medicinal properties that arise from their intriguing chemical structures. The highly-substituted carbocycle is one of the most common structural features in many structurally complicated natural products. However, the construction of highly-substituted, stereo-congested, five-membered carbocycles containing all-carbon quaternary center(s) is, at present, a distinct challenge in modern synthetic chemistry, which can be accessed through the all-carbon [3 + 2] cycloaddition. More importantly, the all-carbon [3 + 2] cycloaddition can forge vicinal all-carbon quaternary centers in a single step and has been demonstrated in the synthesis of complex natural products. In this review, we present the development of all-carbon [3 + 2] cycloadditions and illustrate their application in natural product synthesis reported in the last decade covering 2011-2020 (inclusive).

Synthetic, Mechanistic, and Biological Interrogation of Ginkgo biloba Chemical Space En Route to (-)-Bilobalide

Here we interrogate the structurally dense (1.64 mcbits/Å3) GABAA receptor antagonist bilobalide, intermediates en route to its synthesis, and related mechanistic questions. 13C isotope labeling identifies an unexpected bromine migration en route to an α-selective, catalytic asymmetric Reformatsky reaction, ruling out an asymmetric allylation pathway. Experiment and computation converge on the driving forces behind two surprising observations. First, an oxetane acetal persists in concentrated mineral acid (1.5 M DCl in THF-d8/D2O); its longevity is correlated to destabilizing steric clash between substituents upon ring-opening. Second, a regioselective oxidation of des-hydroxybilobalide is found to rely on lactone acidification through lone-pair delocalization, which leads to extremely rapid intermolecular enolate equilibration. We also establish equivalent effects of (-)-bilobalide and the nonconvulsive sesquiterpene (-)-jiadifenolide on action potential-independent inhibitory currents at GABAergic synapses, using (+)-bilobalide as a negative control. The high information density of bilobalide distinguishes it from other scaffolds and may characterize natural product (NP) space more generally. Therefore, we also include a Python script to quickly (ca. 132 000 molecules/min) calculate information content (Böttcher scores), which may prove helpful to identify important features of NP space.

Identification of the main active antidepressant constituents in a traditional Turkish medicinal plant, Centaurea kurdica Reichardt

ETHNOPHARMACOLOGICAL RELEVANCE

In Turkish folk medicine, infusions and decoctions prepared from the flowers, fruits and aerial parts of Centaurea kurdica Reichardt (Asteraceae) are used as sedative and antidepressant-like effects of various sedative plants have been identified in many studies. The present study was designed to evaluate the antidepressant activity of this plant.

MATERIALS AND METHODS

n-Hexane, ethyl acetate (EtOAc), and methanol (MeOH) extracts were prepared from the branches with leaves and also flowers of the plant. Antidepressant potentials of these extracts were researched by using the forced swimming test, tail suspension test, and antagonism of tetrabenazine-induced ptosis, hypothermia, and suppression of locomotor activity.

RESULTS

After determination of high antidepressant potentials of MeOH extract prepared from flowers and n-hexane extract prepared from branches with leaves, isolation studies were carried out on these two extracts and the main active components were determined as β-amyrin, mixture of β-sitosterol and stigmasterol and costunolide for the branches with leaves and quercitrin, isoquercetin and naringenin-7-O-glucopyranoside for the flowers.

CONCLUSIONS

As a result of the mechanistic and toxicity studies planned on this plant, it is thought that C. kurdica may be a glimmer of hope for depressed patients.

Neurotherapeutic effects of Ginkgo biloba extract and its terpene trilactone, ginkgolide B, on sciatic crush injury model: A new evidence

Ginkgo biloba leaves extract (GBE) was subjected to neuroprotective-guided fractionation to produce eleven fractions with different polarities and constituents. The intermediate polar fraction was shown to be terpene trilactones-enriched fraction (TEGBE). Out of this fraction, pure ginkgolide B (G-B) was further purified and identified based on its spectral data. The effects of GBE and TEGBE were evaluated in comparison to that of G-B in the crush sciatic nerve injury rat model. To evaluate the neuroprotective effects, sixty Wistar male rats were randomly allocated into 6 groups: naive, sham, crush + normal saline, and three treatment groups; crush + GBE, crush + TEGBE, and crush + G-B. Treatments were given one hour following injury, and once daily for 14 days. Neurobehavioral tests, histomorphological examinations, and immunohistochemical analysis of the sciatic nerve and the spinal cord were performed at weeks 3 and 6 post-injury. GBE, TEGBE and G-B were shown to enhance the functional and sensory behavioral parameters and to protect the histological and the ultrastructural elements in the sciatic nerve. Additionally, all treatments prevented spinal cord neurons from further deterioration. It was shown that G-B has the most significant potential effects among all treatments with values that were nearly comparable to those of sham and naive groups.

Concise asymmetric synthesis of (-)-bilobalide

The Ginkgo biloba metabolite bilobalide is widely ingested by humans but its effect on the mammalian central nervous system is not fully understood1-4. Antagonism of γ-aminobutyric acid A receptors (GABAARs) by bilobalide has been linked to the rescue of cognitive deficits in mouse models of Down syndrome5. A lack of convulsant activity coupled with neuroprotective effects have led some to postulate an alternative, unidentified target4; however, steric congestion and the instability of bilobalide1,2,6 have prevented pull-down of biological targets other than the GABAΑRs. A concise and flexible synthesis of bilobalide would facilitate the development of probes for the identification of potential new targets, analogues with differential selectivity between insect and human GABAΑRs, and stabilized analogues with an enhanced serum half-life7. Here we exploit the unusual reactivity of bilobalide to enable a late-stage deep oxidation that symmetrizes the molecular core and enables oxidation states to be embedded in the starting materials. The same overall strategy may be applicable to G. biloba congeners, including the ginkgolides-some of which are glycine-receptor-selective antagonists8. A chemical synthesis of bilobalide should facilitate the investigation of its biological effects and its therapeutic potential.

Bilobalide Suppresses Adipogenesis in 3T3-L1 Adipocytes via the AMPK Signaling Pathway

Bilobalide, the only sesquiterpene compound from Ginkgo biloba leaf, exhibits various beneficial pharmaceutical activities, such as antioxidant, anti-inflammation, and protective effects for the central nervous system. Several bioactive components extracted from Ginkgo biloba extract reportedly have the potential to attenuate lipid metabolism. However, the effect of bilobalide on lipid metabolism remains unclear. In this study, we used 3T3-L1 cells as the cell model to investigate the effect of bilobalide on adipogenesis. The results showed that bilobalide inhibited 3T3-L1 preadipocyte differentiation and intracellular lipid accumulation. Quantitative real-time PCR and western blotting results indicated that several specific adipogenic transcription factors and a few important adipogenesis-related genes were significantly down regulated on both mRNA and protein levels in bilobalide treatment groups. By contrast, the expression of some lipolytic genes, such as adipose triglyceride lipase, hormone-sensitive lipase (HSL), and carnitine palmitoyltransferase-1α, were all up-regulated by bilobalide treatment, and the phosphorylation of AMP-activated protein kinase (AMPK), acetyl-CoA carboxylase 1, and HSL were stimulated. Furthermore, bilobalide treatment partially restored AMPK activity following its blockade by compound C (dorsomorphin). These results suggested that bilobalide inhibited adipogenesis and promoted lipolysis in 3T3-L1 cells by activating the AMPK signaling pathway.

Ginkgo biloba Extract EGb 761 Improves Vestibular Compensation and Modulates Cerebral Vestibular Networks in the Rat

Unilateral inner ear damage is followed by behavioral recovery due to central vestibular compensation. The dose-dependent therapeutic effect of Ginkgo biloba extract EGb 761 on vestibular compensation was investigated by behavioral testing and serial cerebral [¹⁸F]-Fluoro-desoxyglucose ([¹⁸F]-FDG)-μPET in a rat model of unilateral labyrinthectomy (UL). Five groups of 8 animals each were treated with EGb 761-supplemented food at doses of 75, 37.5 or 18.75 mg/kg body weight 6 weeks prior and 15 days post UL (groups A,B,C), control food prior and EGb 761-supplemented food (75 mg/kg) for 15 days post UL (group D), or control food throughout (group E). Plasma levels of EGb 761 components bilobalide, ginkgolide A and B were analyzed prior and 15 days post UL. Behavioral testing included clinical scoring of nystagmus, postural asymmetry, head roll tilt, body rotation during sensory perturbation and instrumental registration of mobility in an open field before and 1, 2, 3, 5, 7, 15 days after UL. Whole-brain [¹⁸F]-FDG-μPET was recorded before and 1, 3, 7, 15 days after UL. The EGb 761 group A (75 mg/kg prior/post UL) showed a significant reduction of nystagmus scores (day 3 post UL), of postural asymmetry (1, 3, 7 days post UL), and an increased mobility in the open field (day 7 post UL) as compared to controls (group E). Application of EGb 761 at doses of 37.5 and 18.75 mg/kg prior/post UL (groups B,C) resulted in faster recovery of postural asymmetry, but did not influence mobility relative to controls. Locomotor velocity increased with higher plasma levels of ginkgolide A and B. [¹⁸F]-FDG-μPET revealed a significant decrease of the regional cerebral glucose metabolism (rCGM) in the vestibular nuclei and cerebellum and an increase in the hippocampal formation with higher plasma levels of ginkgolides and bilobalide 1 and 3 days post UL. Decrease of rCGM in the vestibular nucleus area and increase in the hippocampal formation with higher plasma levels persisted until day 15 post UL. In conclusion, Ginkgo biloba extract EGb 761 improves vestibulo-ocular motor, vestibulo-spinal compensation, and mobility after UL. This rat study supports the translational approach to investigate EGb 761 at higher dosages for acceleration of vestibular compensation in acute vestibular loss.

Discovery of new antidepressant agents: In vivo study on Anthemis wiedemanniana Fisch. & Mey

ETHNOPHARMACOLOGICAL RELEVANCE

Many of the currently available antidepressants have serious adverse effects and are also expensive. Traditional medicines are major sources of original drugs, and their role in effective treatment is remarkable. In Turkish folk medicine, decoctions and infusions are prepared from the flowers of Anthemis wiedemanniana Fisch. & Mey. They exert antispasmodic and sedative effects and are also used for treating urinary inflammations. The present study was designed to evaluate the antidepressant activity of A. wiedemanniana, which is used against central nervous system disorders in Turkish folk medicine.

MATERIALS AND METHODS

n-Hexane, ethyl acetate, and methanol (MeOH) extracts were prepared from the flowers of the plant. The antidepressant potentials of these extracts were evaluated in mouse models using the forced swimming test, tail suspension test, and antagonism of tetrabenazine-induced ptosis, hypothermia, and suppression of locomotor activity. The results were compared with those in control and reference groups, and active constituents of the plant were determined. The MeOH extract of A. wiedemanniana was subjected to various chromatographic separation techniques, leading to the isolation and identification of the active component(s).

RESULTS

After confirmation of the antidepressant activity, the MeOH extract was subjected to successive solvent partitioning using solvents of increasing polarity, yielding four subextracts. Each subextract was tested on the same biological activity models. Fraction B was found to have the highest activity and subjected to further chromatographic separation. Isolated germacronolide-type sesquiterpene lactones were elucidated as tatridin A (1) and tanachin (1-epi-tatridin B) (2), which were responsible for the antidepressant activity of the flowers.

CONCLUSIONS

This study explored the antidepressant potential of A. wiedemanniana. Using bioassay-guided fractionation and isolation techniques, tatridin A and tanachin (1-epi-tatridin B) were determined as the main active components of the flowers. Further antidepressant mechanistic studies should be conducted for exploring the activity of these compounds against depression. This study can be an important step in the discovery of newer antidepressants.

Structure-Dependent Activity of Natural GABA(A) Receptor Modulators

GABA(A) receptors are ligand-gated ion channels consisting of five subunits from eight subfamilies, each assembled in four hydrophobic transmembrane domains. This pentameric structure not only allows different receptor binding sites, but also various types of ligands, such as orthosteric agonists and antagonists, positive and negative allosteric modulators, as well as second-order modulators and non-competitive channel blockers. A fact, that is also displayed by the variety of chemical structures found for both, synthetic as well as nature-derived GABA(A)-receptor modulators. This review covers the literature for natural GABA(A)-receptor modulators until the end of 2017 and discusses their structure-activity relationship.

Natural terpenoids as a promising source for modulation of GABAergic system and treatment of neurological diseases

γ-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter reducing neural excitability in the mammalian central nervous system (CNS) with three subclasses of receptors. Several conventional drugs and compounds modulate the GABAergic system, demonstrating different pharmacological effects. In this review, interactions of natural terpenoids with the GABAergic system are highlighted with relation to disorders like anxiety, insomnia, convulsion, pain, and cognitive deficits. Terpenoids with various structures affect the function of the GABAergic system via dissimilar mechanisms. Most of the discussed compounds interact with GABA receptors, but especially with the GABAA subtype. This may be due to the fact that researchers tend to assess the interaction of compounds using GABAA receptors. However, bilobalide, a sesquiterpene, showed anticonvulsant properties through the activation of glutamic acid decarboxylase (GAD) enzyme, which is a key enzyme in biosynthesis of GABA. Therefore, further studies evaluating and comparing terpenoids of different classes and their interaction with the GABA system, along with their pharmacokinetic properties, could be worthwhile in future studies.

Protection Efficacy of the Extract of Ginkgo biloba against the Learning and Memory Damage of Rats under Repeated High Sustained +Gz Exposure

Repeated high sustained positive Gz (+Gz) exposures are known for the harmful pathophysiological impact on the brain of rats, which is reflected as the interruption of normal performance of learning and memory. Interestingly, extract of Ginkgo biloba (EGb) has been reported to have neuroprotective effects and cognition-enhancing effects. In this study, we are interested in evaluating the protective effects of EGb toward the learning and memory abilities. Morris Water Maze Test (MWM) was used to evaluate the cognitive function, and the physiological status of the key components in central cholinergic system was also investigated. Our animal behavioral tests indicated that EGb can release the learning and memory impairment caused by repeated high sustained +Gz. Administration of EGb to rats can diminish some of the harmful physiological effects caused by repeated +Gz exposures. Moreover, EGb administration can increase the biological activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) but reduce the production of malondialdehyde (MDA). Taken together, our study showed that EGb can ameliorate the impairment of learning and memory abilities of rats induced by repeated high sustained +Gz exposure; the underlying mechanisms appeared to be related to the signal regulation on the cholinergic system and antioxidant enzymes system.

Neurite outgrowth enhancement by jiadifenolide: possible targets

Covering: 1860-2016A mechanistic link may exist between convulsant plant substances typified by picrotoxinin, and 'neurotrophic' sesquiterpenes like jiadifenolide. Picrotoxinin elicits convulsion by anion blockade of the Cys-loop family of neurotransmitter-gated ion channels. These same receptors mediate neuronal development and neurite outgrowth prior to synapse formation. Due to its structural homology with picrotoxin and anisatin, it is possible that jiadifenolide enhances NGF-stimulated neurite outgrowth by modulation of the Cys-loop family of receptors.

Species-dependent and receptor-selective action of bilobalide on the function of constitutive androstane receptor and pregnane X receptor

Bilobalide is a naturally occurring sesquiterpene trilactone with therapeutic potential in the management of ischemia and neurodegenerative diseases such as Alzheimer's disease. In the present study, we investigated the effect of bilobalide on the activity of rat constitutive androstane receptor (rCAR) and rat pregnane X receptor (rPXR) and compared that with human CAR (hCAR) and human PXR (hPXR). Bilobalide activated rCAR in a luciferase reporter gene assay and increased rCAR target gene expression in cultured rat hepatocytes, as determined by the CYP2B1 mRNA and CYP2B enzyme activity (benzyloxyresorufin O-dealkylation) assays. This increase in hepatocyte CYP2B1 expression by bilobalide was not accompanied by a corresponding increase in rCAR mRNA level. In contrast to the activation of rCAR, the activity of rPXR, hCAR, and hPXR was not influenced by this chemical in cell-based reporter gene assays. Consistent with these results, bilobalide did not alter rPXR, hCAR, or hPXR target gene expression in rat or human hepatocytes, as evaluated by the CYP3A23, CYP2B6, CYP3A4 mRNA assays and the CYP3A (testosterone 6β-hydroxylation) and CYP2B6 (bupropion hydroxylation) enzyme activity assays. Bilobalide was not an antagonist of rPXR, hCAR, or hPXR, as suggested by the finding that it did not attenuate rPXR activation by pregnenolone 16α-carbonitrile, hCAR activation by 6-(4-chlorophenyl)imidazo[2,1-b][1,3]thiazole-5-carbaldehyde O-(3,4-dichlorobenzyl)oxime, or hPXR activation by rifampicin in reporter gene assays. In conclusion, bilobalide is an activator of rCAR, whereas it is not a ligand of rPXR, hCAR, or hPXR. Likewise, it is an inducer of rat CYP2B1, but not of rat CYP3A23, human CYP2B6, or human CYP3A4.

The facilitative effects of bilobalide, a unique constituent of Ginkgo biloba, on synaptic transmission and plasticity in hippocampal subfields

Bilobalide, a unique constituent of Ginkgo biloba, has been reported to potentiate population spikes in hippocampal CA1 pyramidal cells and to protect the brain against cell death. In this study, the effects of bilobalide on synaptic transmission and its plasticity in rat hippocampal subfields were electrophysiologically investigated. Bilobalide (50 μM) significantly potentiated the input-output relationship at Schaffer collateral (SC)-CA1 synapses but not at medial perforant path (MPP)-dentate gyrus (DG), lateral perforant path (LPP)-DG, or mossy fiber (MF)-CA3 synapses. Facilitative effects of bilobalide on synaptic plasticity were only observed at MPP-DG synapses, in which the induction of long-term depression was blocked in the presence of bilobalide. However, no effect on synaptic plasticity was observed at SC-CA1 synapses. These results suggest that bilobalide has differential effects on synaptic efficacy in each hippocampal subfield.

Central and local administration of Gingko biloba extract EGb 761® inhibits thermal hyperalgesia and inflammation in the rat carrageenan model

BACKGROUND

Oral administration of the standardized Ginkgo biloba extract EGb 761® has been shown to inhibit thermal hyperalgesia in rodent models of inflammatory and postsurgical pain, but the mechanism underlying these effects is not known. We sought to determine the site of action of EGb 761 by investigating the antihyperalgesic and antiinflammatory properties of EGb 761 after local and central drug administration in the rat carrageenan model of inflammation.

METHODS

Adult male Wistar rats received an intraplantar injection of carrageenan (3%) or saline into the left hindpaw followed 3 hours later by an intraplantar injection of EGb 761 (30, 100, or 300 μg) or vehicle into the left paw; or intrathecal injection of EGb 761 (0.5, 1, 3, 10, or 100 μg) or vehicle into the lumbar spinal cord region. Diclofenac (100 μg) was administered as a positive control. Hindpaw withdrawal latency (in seconds) to thermal stimulation, response threshold (in grams) to mechanical stimulation, and paw volume were measured at 0, 2, 4, 6, and 24 hours after carrageenan injection.

RESULTS

Both intraplantar (30, 100, and 300 μg) and intrathecal (0.5 and 1 μg) EGb 761 significantly inhibited carrageenan-induced thermal hyperalgesia and were equally as effective as diclofenac, but had no effect on mechanical hypersenitivity. Application ≥3 μg EGb 761 to the spinal cord induced adverse behavioral effects, which precluded further nociceptive testing. Intraplantar (300 μg) and intrathecal (1 μg) EGb 761 also significantly reduced paw edema.

CONCLUSION

These studies show that EGb 761 acts both at the site of inflammation and centrally at the spinal cord level to inhibit inflammation and thermal hyperalgesia, and may be useful in the treatment of inflammatory pain.

Ginkgolide B and bilobalide block the pore of the 5-HT₃receptor at a location that overlaps the picrotoxin binding site

Extracts from the Ginkgo biloba tree are widely used as herbal medicines, and include bilobalide (BB) and ginkgolides A and B (GA and GB). Here we examine their effects on human 5-HT₃A and 5-HT₃AB receptors, and compare these to the effects of the structurally related compounds picrotin (PTN) and picrotoxinin (PXN), the two components of picrotoxin (PTX), a known channel blocker of 5-HT₃, nACh and GABA_A receptors. The compounds inhibited 5-HT-induced responses of 5-HT₃ receptors expressed in Xenopus oocytes, with IC₅₀ values of 470 μM (BB), 730 μM (GB), 470 μM (PTN), 11 μM (PXN) and >1 mM (GA) in 5-HT₃A receptors, and 3.1 mM (BB), 3.9 mM (GB), 2.7 mM (PTN), 62 μM (PXN) and >1 mM (GA) in 5-HT₃AB receptors. Radioligand binding on receptors expressed in HEK 293 cells showed none of the compounds displaced the specific 5-HT₃ receptor antagonist [³H]granisetron, confirming that they do not act at the agonist binding site. Inhibition by GB at 5-HT₃A receptors is weakly use-dependent, and recovery is activity dependent, indicating channel block. To further probe their site of action at 5-HT₃A receptors, BB and GB were applied alone or in combination with PXN, and the results fitted to a mathematical model; the data revealed partially overlapping sites of action. We conclude that BB and GB block the channel of the 5-HT₃A receptor. Thus these compounds have comparable, although less potent, behaviour than at some other Cys-loop receptors, demonstrating their actions are conserved across the family.

Evaluation of behavioral and pharmacological effects of Hedyosmum brasiliense and isolated sesquiterpene lactones in rodents

ETHNOPHARMACOLOGICAL RELEVANCE

Hedyosmum brasiliense Miq. (Chloranthaceae) is an essential Brazilian species largely found in the Atlantic Forest. It is popularly known as "cidrão" and in folk medicine, this aromatic species is widely used as a calmative/tranquilizer and to treat sleep disorders.

AIM OF THE STUDY

To examine the neurochemical properties of ethanol extract (EEHb), fractions and compounds of fresh leaves of Hedyosmum brasiliense and the antidepressant effect of the isolated sesquiterpene lactones podoandin and 13-hydroxy-8,9-dehydroshizukanolide.

MATERIALS, METHODS AND RESULTS

The effects of EEHb were demonstrated by the open field, elevated-plus-maze, forced swimming, pentobarbital-induced sleeping time, PTZ-induced seizure, and inhibitory avoidance tests. EEHb did not show a protective effect against PTZ-induced convulsions. In the plus-maze test, EEHb (100mg/kg, i.p.) exhibited an anxiolytic effect through the effective enhancement of the frequency and time spent in the open arms of the maze. Conversely, the time spent and the number of entrances to the closed arms were decreased. All these effects were also completely reversed by pre-treatment with flumazenil (2.5mg/kg, i.p./a benzodiazepine receptor agonist), similar to the results observed with diazepam used as a positive standard. In this test, the anxiolytic effect of EEHb was also totally blocked by pre-treatment with reserpine (2.0mg/kg, i.p.), a drug known to induce depletion of biogenic amines. In the forced swimming test, the treatment of EEHb (100mg/kg, i.p. or 100mg/kg, p.o.) given in acute and chronic form (10, 50 and 100mg/kg), produced a decrease in immobility time, similar to that of imipramine (10mg/kg, i.p.), the positive control. The dichloromethane and hexane fractions (100mg/kg, p.o.) also produced a decrease in immobility time. In addition, the two isolated compounds tested in a single dose (10mg/kg, i.p.), the antidepressant effect was observed only with the compound podoandin, which also caused a decrease in immobility time. EEHb (10-100mg/kg) a dose-dependent manner also caused a decrease in barbiturate sleeping time in mice, and in high doses (100mg/kg), did not interfere in memory consolidation.

CONCLUSIONS

The results suggest that EEHb presents psychopharmacological activities, including anxiolytic, antidepressant, and hypnotic effects.

Bilobalide modulates serotonin-controlled behaviors in the nematode Caenorhabditis elegans

Background

Dysfunctions in the serotonergic system have been implicated in several neurological disorders such as depression. Elderly individuals who have been diagnosed with clinical depression show elevated cases of neurodegenerative diseases. This has led to suggestions that modulating the serotonin (5-HT) system could provide an alternative method to current therapies for alleviating these pathologies. The neuroprotective effects of bilobalide in vitro have been documented. We aim to determine whether bilobalide affects the 5-HT system in the nematode C. elegans. The wild type worms, as well as well-characterized 5-HT mutants, were fed with bilobalide in a range of concentrations, and several 5-HT controlled behaviors were tested.

Results

We observed that bilobalide significantly inhibited 5-HT-controlled egg-laying behavior in a dose-dependent manner, which was blocked in the 5-HT receptor mutants (ser-4, mod-1), but not in the 5-HT transporter (mod-5) or synthesis (tph-1) mutants. Bilobalide also potentiated a 5-HT-controlled, experience-dependent locomotory behavior, termed the enhanced slowing response in the wild type animals. However, this effect was fully blocked in 5-HT receptor mod-1 and dopamine defective cat-2 mutants, but only partially blocked in ser-4 mutants. We also demonstrated that acetylcholine transmission was inhibited in a transgenic C. elegans strain that constitutively expresses Aβ, and bilobalide did not significantly affect this inhibition.

Conclusion

These results suggest that bilobalide may modulate specific 5-HT receptor subtypes, which involves interplay with dopamine transmission. Additional studies for the function of bilobalide in neurotransmitter systems could aid in our understanding of its neuroprotective properties.

Preventive and curative effects of etifoxine in a rat model of brain oedema

1. The aim of the present study was to test the hypothesis that increasing GABAergic neurotransmission is involved in the prevention or treatment of brain oedema. The study was conducted in the well-established rat triethyltin (TET) model of brain oedema and examined the effects of etifoxine, a compound that increases GABAergic neurotransmission through multiple mechanisms, including neurosteroid synthesis. 2. Daily oral administration of 3 mg/kg per day TET for 5 consecutive days strongly perturbed rat behaviour and induced reproducible cerebral oedema. Coadministration of etifoxine (2 x 25 or 2 x 50 mg/kg per day, p.o.) over the 5 days of TET treatment blocked the development of brain oedema and the increase in brain sodium content induced by TET, as well as reducing the increase in brain chloride content. Moreover, etifoxine inhibited the decrease in bodyweight, the neurological deficit and the altered locomotor activity induced by TET. At a lower dose (2 <--> 10 mg/kg per day, p.o.), etifoxine did not have any preventive effects. 3. To examine the curative effects of etifoxine, it was administered from the 4th day of TET treatment for 5 consecutive days, when brain oedema was already established. In these experiments, etifoxine (2 <--> 50 mg/kg per day, p.o.) significantly reduced cerebral oedema and the outcomes induced by TET treatment. Moreover, etifoxine reduced the mortality in response to TET treatment. 4. In conclusion, because etifoxine has a good safety profile as an anxiolytic, the results of the present study suggest that it is worth further clinical investigation as a neuroprotectant.

Ginkgo biloba extract EGb 761 attenuates hippocampal neuronal loss and cognitive dysfunction resulting from chronic restraint stress in ovariectomized rats

We have recently found that a combination of ovariectomy (OVX) and chronic restraint stress causes cognitive dysfunction and reduces hippocampal CA3 neurons in female rats and that estrogen replacement suppresses the OVX/stress-induced behavioral and morphological changes. In this study, we examined the effect of Ginkgo biloba extract (EGb 761), a popular herbal supplement, on the cognitive dysfunction and neuromorphological change in OVX/stress-subjected rats. Female Fisher 344 rats were randomly divided into three groups: vehicle-treated OVX, EGb 761 (50 mg/kg) -treated OVX and vehicle-treated sham-operated control groups. Two months after ovariectomy, all animals received restraint stress for 21 days (6 h/day), and were then subjected to a novel object recognition test followed by morphological examination by Nissl staining. EGb 761 was orally administered once daily until the behavioral analysis was done. Treatment with EGb 761 improved memory impairment and neuronal loss of hippocampus in the OVX/stress-subjected group in the same ways as 17beta-estradiol. On the other hand, EGb 761 did not affect the loss of bone mineral density and increase in body weight after OVX, although 17beta-estradiol attenuated them. These results have important implications for neuroprotective and cognition enhancing effects of EGb 761 in postmenopausal women and suggest that the effects are mediated by a different mechanism from estrogen.

Chromatographic fingerprint analysis for evaluation of Ginkgo biloba products

The flavonoids and the terpene lactones are regarded as the two main active components of Ginkgo biloba that affect human health. In the work discussed in this paper, two analytical methods for the characterization of G. biloba authentic materials and commercial products, an LC-UV chromatographic fingerprinting method and a traditional flavonol quantification method, were compared. The traditional method was used to determine the total flavonol content (as glycosides) after acid hydrolysis. The fingerprinting method examined the chromatographic profiles of methanol-water extracts using chemometric methods. The traditional method showed that all the commercial products met the current voluntary standard of 24% flavonols by weight. The chromatographic fingerprinting method revealed significant variations in the commercial products with regard to the relative concentration of individual flavonols.