Application of radioligand receptor binding assays in the search for CNS active principles from Chinese medicinal plants

Pistacia vera Extract Potentiates the Effect of Melatonin on Human Melatonin MT1 and MT2 Receptors with Functional Selectivity

Melatonin is a tryptophan derivative synthesized in plants and animals. In humans, melatonin acts on melatonin MT₁ and MT₂ receptors belonging to the G protein-coupled receptor (GPCR) family. Synthetic melatonin receptor agonists are prescribed for insomnia and depressive and circadian-related disorders. Here, we tested 25 commercial plant extracts, reported to have beneficial properties in sleep disorders and anxiety, using cellular assays (2─[¹²⁵I]iodomelatonin binding, cAMP inhibition, ERK1/2 activation and β-arrestin2 recruitment) in mock-transfected and HEK293 cells expressing MT₁ or MT₂. Various melatonin receptor-dependent and -independent effects were observed. Extract 18 (Ex18) from Pistacia vera dried fruits stood out with very potent effects in melatonin receptor expressing cells. The high content of endogenous melatonin in Ex18 (5.28 ± 0.46 mg/g extract) is consistent with this observation. Ex18 contains an additional active principle that potentiates the effect of melatonin on G_i protein-dependent pathways but not on β-arrestin2 recruitment. Further active principles potentiating exogenous melatonin were detected in several extracts. In conclusion, we identified plant extracts with various effects in GPCR-based binding and signalling assays and identified high melatonin levels and a melatonin-potentiating activity in Pistacia vera dried fruit extracts that might be of therapeutic potential.

Protective effect of compatible herbs in Jin-Gu-Lian formula against Alangium chinense-induced neurotoxicity via oxidative stress, neurotransmitter metabolisms, and pharmacokinetics

Background: A. chinense frequently used in Miao medicine to treat rheumatic diseases. However, as a famous toxic herb, Alangium chinense and its representative components exhibit ineluctable neurotoxicity, thus creating significant challenges for clinical application. The combined application with compatible herbs in Jin-Gu-Lian formula attenuates such neurotoxicity according to the compatible principle of traditional Chinese medicines. Purpose: We aimed to investigate the detoxification of the compatible herbs in Jin-Gu-Lian formula on A. chinense-induced neurotoxicity and investigate its mechanism. Methods: Neurobehavioral and pathohistological analysis were used to determine the neurotoxicity in rats administered with A. chinense extract (AC), extract of compatible herbs in Jin-Gu-Lian formula (CH) and combination of AC with CH for 14 days. The mechanism underlying the reduction of toxicity by combination with CH was assessed by enzyme-linked immunosorbent assays, spectrophotometric assays, liquid chromatography tandem-mass spectrometry and real-time reverse transcription-quantitative polymerase chain reaction. Results: Compatible herbs attenuated the AC-induced neurotoxicity as evidenced by increased locomotor activity, enhanced grip strength, the decreased frequency of AC-induced morphological damage in neurons, as well as a reduction of neuron-specific enolase (NSE) and neurofilament light chain (NEFL) levels. The combination of AC and CH ameliorated AC-induced oxidative damage by modulating the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), and total antioxidant capacity (T-AOC). AC treatment significantly reduced the levels of monoamine and acetylcholine neurotransmitters in the brains of rats, including acetylcholine (Ach), dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), norepinephrine (NE), and serotonin (5-HT). Combined AC and CH treatment regulated the abnormal concentrations and metabolisms of neurotransmitters. Pharmacokinetic studies showed that the co-administration of AC and CH significantly decreased plasma exposure levels of two main components of AC, as evidenced by the reduction of maximum plasma concentration (C_max), area under the plasma concentration-time curve (AUC) compared to AC. In addition, the AC-induced downregulation in mRNA expression of cytochrome P450 enzymes was significantly reduced in response to combined AC and CH treatment. Conclusion: Compatible herbs in Jin-Gu-Lian formula alleviated the neurotoxicity induced by A. chinense by ameliorating oxidative damage, preventing abnormality of neurotransmitters and modulating pharmacokinetics.

Genus Alangium - A review on its traditional uses, phytochemistry and pharmacological activities

The species from Alangium have been used as folk medicine to treat rheumatism, skin diseases, diabetes by the people of Southeast Asia. Previous phytochemical studies have shown this genus are rich sources of alkaloids, glycosides, and terpenoids, which have attracted considerable attention of many researchers due to their markedly diverse and complex architecture. The crude extracts as well as the monomeric compounds from the title genus possess anti-tumor, anti-inflammatory, antibacterial, anti-oxidant pharmacological activities. Besides, some isolates from Alangium exhibited the effects on skeletal, smooth muscle and the nervous system. As a large genus of medicinal plants, the medicinal value of Alangium has been widely reported, but there is no review that provide a systematic summary towards its chemical constituents and pharmacological activities, to our knowledge. This work aims to present a comprehensive overview on the traditional uses, phytochemistry, and pharmacological activities of medicinal plants in the genus Alangium, and to explore the evidence supporting its ethnopharmacological effectiveness.

Shuangxia decoction alleviates p-chlorophenylalanine induced insomnia through the modification of serotonergic and immune system

As a Traditional Chinese Medicine (TCM), Shuangxia Decoction (SXD) has been used to treat insomnia in oriental countries for more than thousands of years and it presents remarkable clinical effects. However, its active pharmacological fraction and the mechanism of sedative-hypnotic effects have not been explored. In this paper, we investigated active pharmacological fraction and revealed the detailed mechanisms underlying the sedative-hypnotic effects of SXD. It showed that SXD water extract compared to ethanol extract possessed better sedative effects on locomotion activity in normal mice and increased sleep duration in subhypnotic dose of sodium pentobarbital-treated mice. SXD alleviated p-chlorophenylalanine (PCPA) -induced insomnia by increasing the content of 5-HT in cortex [F (4, 55) = 12.67], decreasing the content of dopamine (DA) and norepinephrine (NE). Furthermore, SXD enhanced the expression of 5-HT_1A and 5-HT_2A receptors in hypothalamic and reduced serum levels of IL-1,TNF-α [F (5, 36) = 15.58]. In conclusion, these results indicated that SXD produced beneficial sedative and hypnotic bioactivities mediated by regulating the serotonergic and immune system.

Serotonin Receptor Binding Characteristics of Geissoschizine Methyl Ether, an Indole Alkaloid in Uncaria Hook

Background:

Geissoschizine methyl ether (GM) is one of the indole alkaloids in Uncaria hook, and an active ingredient of yokukansan (YKS) that improves behavioral and psychological symp-toms of dementia (BPSD) in patients with several types of dementia. The pharmacological action of GM has been related to various serotonin (5-HT) receptor subtypes.

Objective:

The aim of this article is to review the binding characteristics of GM to the 5-HT receptor sub-types in the brains using our own data and previous findings.

Methods:

Competitive receptor-binding and agonist/antagonist activity assays for several 5-HT receptor subtypes were performed. Moreover, the articles describing pharmacokinetics and brain distribution of GM were searched in PubMed.

Results:

GM bound the following 5-HT receptor subtypes: 5-HT1A, 5-HT1B, 5-HT2A, 5-HT2B, 5-HT2C, 5-HT4, 5-HT5A, 5-HT6, and 5-HT7. Among these receptors, GM had partial agonistic activity for 5-HT1A receptors and antagonistic activity for 5-HT2A, 5-HT2B, 5-HT2C, and 5-HT7 receptors. Also, GM was me-tabolized by various CYP isoforms, mainly CYP3A4. Parent/unchanged GM was detected in both the blood and brain of rats after oral administration of YKS. In the brains, GM was presumed to bind to 5-HT1A, 5-HT2A, 5-HT2B, 5-HT2C, and 5-HT7 receptors on neuron-like large cells mainly in the frontal cor-tex.

Conclusion:

These results suggest that GM is a pharmacologically important alkaloid that regulates vari-ous serotonergic activities or functions by binding to multiple 5-HT receptor subtypes. Thus, this review provides recent 5-HT receptor-related evidence that GM is partly responsible for pharmacological effects of YKS.

Study on the hypnotic effect of rare protopanaxadiol-type and protopanaxatriol-type ginsenosides

Ginsenosides, as major active components of ginseng, possess various pharmacological activities, including anti-tumor, anti-diabetic and hypotensive effects. However, the sedative and hypnotic effect of ginsenosides and the involved mechanism remain unclear. In the present study, the hypnotic effect of rare protopanaxadiol-type (PD) ginsenosides, consisting of Rg3, Rk1, Rg5, and protopanaxatriol-type (PT) ginsenosides, consisting of Rh1, Rk3, Rh4, was investigated and compared in rodent models through behavioral pharmacology methods. Both rare PD and PT ginsenosides decreased spontaneous locomotion activity in normal mice and reduced sleep latency, and extended sleep duration in pentobarbital-treated mice. Moreover, PD and PT ginsenosides attenuated the insomnia induced by caffeine in mice. These hypnotic effects of PD and PT ginsenosides were potentiated by 5-hydroxytryptophan (5-HTP), a precursor of serotonin, and inhibited by p-chlorophenylalanine (PCPA), a 5-HT synthesis inhibitor. Flumazenil (FLU, a specific gamma aminobutyric acid (GABA) antagonist) also impaired the hypnotic effect of both PD and PT ginsenosides. The aforementioned results indicated that PD and PT ginsenosides exhibit sedative and hypnotic activity, and PT ginsenosides show higher activity than PD ginsenosides at high doses (96 mg kg⁻¹). Furthermore, the bioactivity of these two types of ginsenosides might be mediated via the serotonergic and GABAergic systems.

Ginsenosides, as major active components of ginseng, possess various pharmacological activities, including anti-tumor, anti-diabetic and hypotensive effects.

4-Hydroxybenzyl alcohol derivatives and their sedative–hypnotic activities

4-Hydroxybenzyl alcohol (HBA), one of the characteristic active components of Gastrodia elata, exhibits obvious effects on the human central nervous system. In order to acquire compounds with superior bioactivity, 10 derivatives of HBA were synthesized from HBA and carboxylic acids. The sedative effects of the 10 HBA derivatives were evaluated using a spontaneous locomotor activity test (SLT) in mice, and their hypnotic effects were determined to be synergistic with pentobarbital-induced sleep. The results showed that 4-hydroxybenzyl alcohol 3-furancarboxylic acid diester (2FHBA, 10 mg kg⁻¹) exhibited the strongest sedative–hypnotic activity among HBA and its derivatives, and 2FHBA could reverse the insomnia caused by p-chlorophenylalanine (pCPA), flumazenil (FLU) and thiosemicarbazide (TSC). Meanwhile, 2FHBA and 5-hydroxytryptophan (5-HTP) showed a synergistic effect. The results suggested that 2FHBA might be a potential agent against insomnia, which might be mediated by the serotonergic and GABAergic systems.

2FHBA, a derivative of HBA, exerts sedative and hypnotic effects through the serotonergic and GABAergic systems.

Interaction of Plant Extracts with Central Nervous System Receptors

Background: Plant extracts have been used in traditional medicine for the treatment of various maladies including neurological diseases. Several central nervous system receptors have been demonstrated to interact with plant extracts and components affecting the pharmacology and thereby potentially playing a role in human disease and treatment. For instance, extracts from Hypericum perforatum (St. John’s wort) targeted several CNS receptors. Similarly, extracts from Piper nigrum, Stephania cambodica, and Styphnolobium japonicum exerted inhibition of agonist-induced activity of the human neurokinin-1 receptor. Methods: Different methods have been established for receptor binding and functional assays based on radioactive and fluorescence-labeled ligands in cell lines and primary cell cultures. Behavioral studies of the effect of plant extracts have been conducted in rodents. Plant extracts have further been subjected to mood and cognition studies in humans. Results: Mechanisms of action at molecular and cellular levels have been elucidated for medicinal plants in support of standardization of herbal products and identification of active extract compounds. In several studies, plant extracts demonstrated affinity to a number of CNS receptors in parallel indicating the complexity of this interaction. In vivo studies showed modifications of CNS receptor affinity and behavioral responses in animal models after treatment with medicinal herbs. Certain plant extracts demonstrated neuroprotection and enhanced cognitive performance, respectively, when evaluated in humans. Noteworthy, the penetration of plant extracts and their protective effect on the blood-brain-barrier are discussed. Conclusion: The affinity of plant extracts and their isolated compounds for CNS receptors indicates an important role for medicinal plants in the treatment of neurological disorders. Moreover, studies in animal and human models have confirmed a scientific basis for the application of medicinal herbs. However, additional investigations related to plant extracts and their isolated compounds, as well as their application in animal models and the conducting of clinical trials, are required.

Clerodendrum serratum (L.) Moon. - a review on traditional uses, phytochemistry and pharmacological activities

ETHNOPHARMACOLOGICAL RELEVANCE

Clerodendrum serratum (L.) Moon. (Verbenaceae) is an important medicinal plant growing in the tropical and warm temperate regions like Africa, Southern Asia; Malaysia and distributed throughout in forests of India and Sri Lanka. It is traditionally valued and reported for treating pain, inflammation, rheumatism, respiratory disorders, fever and malarial fever in India with a long history. To provide a comprehensive overview of the traditional and ethno medicinal uses, phytochemistry and biological activities of C. serratum with clinical and toxicity data and possibly make recommendations for further research.

MATERIALS AND METHODS

All relevant worldwide accepted databases were searched for the terms "Clerodendrum", "Clerodendrum serratum", "Bharangi" and "Cheruthekku" along with the other literature from Indian classical texts and pharmacopoeias. There was no specific timeline set for the search. The accessible literatures available on C. serratum were collected via electronic search using Pubmed, Scopus, Science Direct and traditional books reports on ethnopharmacology and traditional medicines.

RESULTS

C. serratum has played an important role in Indian system of medicine. In addition to the common local use in respiratory diseases, other ethnomedicinal uses include treatment of pain, inflammation, rheumatism and fever especially malarial fever. Scientific studies on extracts and formulations revealed anti-asthmatic, mast cell stabilization and anti-allergic effects of roots of C. serratum. Reported data on pharmacological activities also includes hepatoprotective, anti-oxidant, anti-inflammatory and anticancer potential of the drug. Saponins (terpenoids and steroids), flavonoids and phenolics isolated from roots have been the focus of phytochemical investigations as the biological activity has been ascribed to the saponins, which are known to possess anti-inflammatory and anti-cancer activity. Isolated bioactives from roots like icosahydropicenic acid and ursolic acid have been claimed to offer anti-allergic and hepatoprotective activity.

CONCLUSIONS

Therapeutic potential of roots and leaves of C. serratum has been demonstrated in the conditions like asthma, allergy, fever, inflammation and liver disorders attributed to the presence of various flavonoids, phenolics and saponins present in the drug. Many ethnobotanical claims have been confirmed through modern in-vitro and in-vivo pharmacological studies of different extracts and isolates from plant; however, additional studies on the biomarkers are needed to establish mechanism of action and to validate the traditional use of this drug in clinical practices after proper safety assessment.

Comprehensive review of Clerodendrum phlomidis: a traditionally used bitter

Clerodendrum phlomidis Linn. f., (syn. Clerodendrum multiflorum (Burm.f) O. Kuntze, Volkameria multiflorum Burm. f.) (Lamiaceae) is an important and well known medicinal plant extensively used in Ayurveda and Siddha system of medicine for treatment of various ailments. The popular therapies include on inflammation, diabetes, nervous disorder, asthma, rheumatism, digestive disorders, and urinary disorders as well as a bitter tonic. It was reported that pectolinaringenin, scutellarein, clerodin, clerodendrin, clerosterol, 24beta-ethylcholesta-5,22E,25-triene-3beta-ol, lup-20(29)-en-3-triacontanoate, 4,2',4'-trihydroxy-6'-methoxychalcone-4,4'alpha-D-diglucoside, 7-hydroxyflavone, 7-hydroxyflavanone-7-O-glucoside and alpha-L-rhamnopyranosyl-(1-2)alpha-D-glucopyranosyl-7-O-naringin-4'-O-alpha-D-glucopyranoside-5-methyl ether had been isolated from this plant. The alcoholic and aqueous extracts were reported active as analgesic, antidiarrhoeal, antiplasmodial, hypoglycemic, minor tranquilizers, anti-asthmatic, antifungal, nematicidal, anti-amnestic and anti-arthritic. There are coincidences between some of the traditional usages of this plant and experimentally observed effects of the extracts but very few biological studies available on bioactive fractions and/or pure compounds. This review is an attempt to compile the exhaustive literature on Clerodendrum phlomidis, to highlight, analyze and critically assess the pharmaceutical potential of this underestimated plant in a systematic way.

Antinociceptive and hypnotic properties of Celastrus orbiculatus

ETHNOPHARMACOLOGICAL RELEVANCE

Celastrus orbiculatus, a woody vine of the Celastraceae family, has been widely used as a traditional medicine for the treatment of many diseases, including rheumatoid arthritis and odontalgia. In this study, we assessed the sedative and antinociceptive activities of the methanolic extract of Celastrus orbiculatus (MCO).

MATERIALS AND METHODS

The antinociceptive effect of MCO was evaluated using several experimental pain models, including thermal nociception methods, such as the tail immersion and the hotplate tests, as well as chemical nociception induced by intraperitoneal acetic acid and subplantar formalin administration in mice. To verify the possible connection of the opioid receptor to the antinociceptive activity of MCO, we performed a combination test with naloxone, a nonselective opioid receptor antagonist. The sedative effect of MCO was studied using the pentobarbital-induced sleeping model.

RESULTS

MCO demonstrated strong and dose-dependent antinociceptive activity compared to tramadol and indomethacin in various experimental pain models. The combination test using naloxone revealed that the antinociceptive activity of MCO is associated with activation of the opioid receptor. MCO also caused decreased sleep latency and increased sleeping time in the pentobarbital-induced sleeping model; however, MCO alone did not induce sleep.

CONCLUSIONS

In the present study, MCO showed potent antinociceptive and sedative activities. Based on these results, MCO may be considered a valuable anti-nociceptive and hypnotic agent for the treatment of various diseases.

Isoliquiritigenin, a chalcone compound, is a positive allosteric modulator of GABAA receptors and shows hypnotic effects

Isoliquiritigenin (ILTG) is a chalcone compound and has valuable pharmacological properties such as antioxidant, anti-inflammatory, anticancer, and antiallergic activities. Recently, the anxiolytic effect of ILTG has been reported; however, its action mechanism and hypnotic activity have not yet been demonstrated. Therefore, we investigated the hypnotic effect and action mechanism of ILTG. ILTG significantly potentiated the pentobarbital-induced sleep in mice at doses of 25 and 50mg/kg. The hypnotic activity of ILTG was fully inhibited by flumazenil (FLU), a specific gamma-aminobutyric acid type A (GABA(A))-benzodiazepine (BZD) receptor antagonist. The binding affinity of ILTG was 0.453 μM and was found to be higher than that of the reference compound, diazepam (DZP, 0.012 μM). ILTG (10(-5)M) potentiated GABA-evoked currents to 151% of the control level on isolated dorsal raphe neurons. ILTG has 65 times higher affinity for GABA(A)-BZD receptors than DZP, and the dissociation constant for ILTG was 4.0 × 10(-10)M. The effect of ILTG on GABA currents was blocked by 10(-7)M FLU and ZK-93426. These results suggest that ILTG produces hypnotic effects by positive allosteric modulation of GABA(A)-BZD receptors.

Phlorotannins of the edible brown seaweed Ecklonia cava Kjellman induce sleep via positive allosteric modulation of gamma-aminobutyric acid type A-benzodiazepine receptor: A novel neurological activity of seaweed polyphenols

The primary objective was to investigate whether seaweeds have hypnotic activity. Methanol extracts of 30 seaweeds were screened for their binding activity at the GABA type A-benzodiazepine (GABA_A-BZD) receptor, a well-characterised molecular target for sedative-hypnotics. The most active seaweed was Ecklonia cava Kjellman (ECK). An ethanol extract of ECK (ECK-E) significantly potentiated pentobarbital-induced sleep in mice. In four solvent fractions separated from ECK-E, hypnotic activity was proportional to contents of total phenols and total phlorotannins, known as seaweed polyphenols. Major phlorotannins of the ethyl acetate (EtOAc) fraction with the highest activity were eckol, eckstolonol, dieckol, and triphlorethol-A, and their K_i (binding affinity, μM) values for [³H]-flumazenil binding were 1.070, 1.491, 3.072, and 4.419, respectively. Hypnotic effects of ECK-E and the EtOAc fraction were fully inhibited by flumazenil, a specific GABA_A-BZD receptor antagonist. These results imply that phlorotannins of ECK induce sleep by positive allosteric modulation of the GABA_A-BZD receptor.

Receptor screening technologies in the evaluation of Amazonian ethnomedicines with potential applications to cognitive deficits

ETHNOPHARMACOLOGICAL RELEVANCE

Amazonian peoples utilize a variety of psychoactive plants that may contain novel biologically active compounds. Efforts to investigate such remedies in terms of neuropharmacology have been limited.

AIM OF THIS STUDY

This study identified Amazonian ethnomedicines with potential for the treatment of cognitive deficits in schizophrenia and dementias, and characterized their interactions with CNS neurotransmitter receptors in vitro.

MATERIALS AND METHODS

Approximately 300 Amazonian species with folk uses or constituents indicative of central nervous system activity were incorporated into a database constructed from literature searches, herbarium surveys, and interviews with traditional practitioners. Approximately 130 of these targeted species were collected in Loreto province, Peru, and 228 fractions derived from them were screened in 31 radioreceptor assays via the resources of the NIMH Psychoactive Drug Screening Program. A subset was also screened in functional assays at selected serotonin, muscarinic, and adrenergic receptors.

RESULTS

Ninety-one samples displayed ≥60% inhibition of radioligand binding activity in receptor assays; 135 samples displayed agonist or antagonist activity (or both) in functional assays.

CONCLUSIONS

Potential CNS activity was detected in about 40% of the samples screened, with some correlations to both folk uses and phytochemical constituents. These results may point to novel and potentially therapeutic CNS active compounds.

Partial agonistic effect of yokukansan on human recombinant serotonin 1A receptors expressed in the membranes of Chinese hamster ovary cells

ETHNOPHARMACOLOGICAL RELEVANCE

Yokukansan (YKS) is a traditional Japanese medicine consisted of seven medicinal herbs and has been used for treatment of neurosis, insomnia, and behavioral and psychological symptoms of dementia (BPSD) in Japan.

AIM OF THE STUDY

The aim of the present study is to clarify the intrinsic activity of YKS on serotonin (5-HT)1A and 5-HT2A receptors and also to determine the constituent herbs which are responsible for the effect of YKS.

MATERIALS AND METHODS

The dry powdered extracts of YKS, seven constituent herbs, and YKS-analogues which were produced by eliminating one of the constituent herbs from YKS in the manufacturing process, were used for the evaluation. Competitive binding assays for 5-HT receptors and [(35)S]GTPgammaS binding assays for the evaluation of agonistic/antagonistic activity were performed using Chinese hamster ovary cell membranes stably expressing human recombinant 5-HT1A or 5-HT2A receptors.

RESULTS

YKS (6.25-400 microg/ml) concentration-dependently inhibited the binding of [(3)H]8-OH-DPAT to 5-HT1A receptors. The IC(50) value was estimated to be 61.2 microg/ml. In contrast, YKS failed to inhibit the binding of [(3)H]ketanserin to 5-HT2A receptors. Only Uncaria hook (3.13-50 microg/ml), of the seven constituent herbal extracts, inhibited the [(3)H]8-OH-DPAT binding to 5-HT1A receptors in a concentration-dependent manner, and the IC(50) value was estimated to be 7.42 microg/ml. The extracts of YKS or Uncaria hook increased [(35)S]GTPgammaS binding to 5-HT1A receptors to approximately 50% of that of a full agonist, 5-HT. Both the competitive binding and [(35)S]GTPgammaS binding of YKS to 5-HT1A receptors were remarkably attenuated by eliminating Uncaria hook from YKS, but it was almost unchanged when one of the other constituent herbs was eliminated from YKS.

CONCLUSION

These results suggest that YKS has a partial agonistic effect on 5-HT1A receptors, which is mainly attributed to Uncaria hook.

Effect of yokukansan, a traditional Japanese medicine, on social and aggressive behaviour of para-chloroamphetamine-injected rats

Objectives

Yokukansan, a traditional Japanese medicine, has been approved by the Ministry of Health, Labour, and Welfare of Japan as a remedy for neurosis, insomnia or night crying and irritability in children. It has recently been reported to improve behavioural and psychological symptoms of dementia, such as hallucinations, agitation, and aggressiveness in patients with some forms of senile dementia. Little is known about the mechanism underlying the effectiveness of yokukansan. Our aim was to clarify the involvement of yokukansan in serotonergic function in para-chloroamphetamine (PCA)-induced aggressive behaviour in rats.

Methods

The effect of yokukansan on social interactions, including social and aggressive behaviour, was examined in PCA-injected rats. Concentration and release level of serotonin (5-HT) in the hypothalamus were measured.

Key findings

PCA reduced not only the 5-HT concentration but also the high K+ -induced 5-HT release in the rat hypothalamus. Social interaction tests showed a significant decrease in social behaviour and a significant increase in aggressive behaviour in the PCA-treated rats. The decrease in social behaviour was ameliorated by the 5-HT1A agonist buspirone and further decreased by a 5-HT1A antagonist, N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclo-hexanecarboxamide trihydrochloride (WAY-100635), whereas it was further decreased by the 5-HT2A agonist, 2,5-dimethoxy-4-iodoamphetamine (DOI), and ameliorated by the 5-HT2A antagonist ketanserin. On the other hand, the increase in aggressive behaviour was ameliorated by buspirone but not affected by WAY-100635, whereas it was enhanced by DOI and ameliorated by ketanserin. A single injection of yokukansan ameliorated the PCA-induced decrease in social behaviour but not aggressive behaviour. Chronic treatment for 14 days with yokukansan ameliorated PCA-induced abnormal behaviour, decreased social behaviour and increased aggressive behaviour, but it did not ameliorate PCA-induced decreases in the cerebral 5-HT concentration and 5-HT release. The ameliorative effects of chronic yokukansan on behaviour were counteracted by co-administration of WAY-100635.

Conclusions

These results suggest that yokukansan might have two different effects: an acute effect on social behaviour and a chronic effect on aggressive behaviour. One of the mechanisms of these effects of yokukansan may be related to the agonistic effect on 5-HT1A receptors.

Anxiolytic effects of the aqueous extract of Uncaria rhynchophylla

The purpose of this study was to characterize the putative anxiolytic-like effects of the aqueous extract of hooks with stem of Uncaria rhynchophylla using the elevated plus maze (EPM) and the hole-board apparatus in rats and mice. Control rats were treated with an equal volume of saline, and positive control rats with buspirone (1 mg/kg). Single or repeated treatments of the aqueous extract of Uncaria rhynchophylla (200 mg/kg/day, p.o.) for 7 days significantly increased the time-spent and entries into open arms of the EPM, and reduced the time-spent and entries into the closed arms versus saline controls (P<0.05). However, no changes in spontaneous locomotor activity or myorelaxant effects were observed versus saline controls. In the hole-board test, repeated treatment with the aqueous extract of Uncaria rhynchophylla (100 or 200 mg/kg/day, p.o.) significantly increased the number of head-dips (P<0.05). In addition, the anxiolytic-like effects of Uncaria rhynchophylla extract as assessed using the EPM test were abolished by WAY 100635 (0.3 mg/kg, i.p.), a 5-HT(1A) receptor antagonist. These results suggest that Uncaria rhynchophylla is an effective anxiolytic agent, and acts via the serotonergic nervous system.

Pharmacological studies of the aqueous extract of Sapindus trifoliatus on central nervous system: possible antimigraine mechanisms

The aqueous extract of pericarp of fruits of Sapindus trifoliatus (ST) Linn., family Sapindaceae was evaluated for its potential effects on central nervous system in mice. The extract at doses 20 and 100 mg/kg, i.p. significantly (p < 0.001) reduced the spontaneous locomotor activity and at 100 mg/kg, increased the thiopental-induced sleeping time. In rota-rod motor co-ordination test, ST at 100 mg/kg, i.p. significantly (p < 0.05-0.01) reduced the endurance time. Further ST exhibited no protection against maximal electroshock (MES)- and pentylenetetrazole (PTZ)-induced convulsions in mice. In receptor radioligand binding studies, ST exhibited affinity towards dopaminergic, alpha-adrenergic and muscarnic receptors. The findings suggest that, ST may possess principles with potential neuroleptic properties.

Effect of Sapindus trifoliatus on hyperalgesic in vivo migraine models

Phytotherapies have offered alternative sources of therapy for migraine and gained much importance in prophylactic treatment. Sapindus trifoliatus is a medium-sized deciduous tree growing wild in south India that belongs to the family Sapindaceae. The pericarp is reported for various medicinal properties. A thick aqueous solution of the pericarp is used for the treatment of hemicrania, hysteria or epilepsy in folklore medicine. We have investigated the antihyperalgesic effects of the lyophilized aqueous extract of S. trifoliatus in animal models predictive of experimental migraine models using morphine withdrawal-induced hyperalgesia on the hot-plate test and on 0.3% acetic acid-induced abdominal constrictions in adult male Swiss albino mice. The extract significantly (N = 10, P < 0.05) increased the licking latency in the hot-plate test when administered i.p. at 10 mg/kg (6.70 +/- 0.39 s in saline control vs 18.76 +/- 0.96 s in S. trifoliatus-treated animals) and significantly (N = 10, P < 0.001) reduced the abdominal constrictions when administered i.p. at 2 and 10 mg/kg (40.20 +/- 1.36 in saline control vs 30.20 +/- 1.33 and 23.00 +/- 0.98 for 2 and 10 mg/kg, i.p., respectively, in S. trifoliatus-treated animals). Furthermore, when administered i.p. at 20 and 100 mg/kg, the extract significantly (N = 10, P < 0.05) inhibited the apomorphine-induced climbing behavior in mice (climbing duration 15.75 +/- 5.0 min for saline control vs 11.4 +/- 1.28 and 3.9 +/- 1.71 min for 20 and 100 mg/kg, respectively, in S. trifoliatus-treated animals). In receptor radioligand-binding studies, the extract exhibited affinity towards D2 receptors. The findings suggest that dopamine D2 antagonism could be the mechanism involved in the antihyperalgesic activity of the aqueous extract of S. trifoliatus.

Effect on locomotion of indole alkaloids from the hooks of uncaria plants

Three predominant Uncariae plants, Uncaria rhynchophylla U. sinensis and U. macrophylla and their indole and oxindole alkaloid constituents were studied for their effect on locomotor response. Water extracts of U. macrophylla and U. sinensis and four indole alkaloids, corynoxine, corynoxine B, isorhynchophylline and geissoschizine methyl ether, significantly decreased locomotor activity after oral administration to mice. The depression of locomotor activity upon administration of these alkaloids appears to be due to mediating of the central dopaminergic system.