Anxiolytic effects of the aqueous extract of Uncaria rhynchophylla

doi:10.1016/j.jep.2006.05.019

Journal of Ethnopharmacology

Volume 108, Issue 2, 24 November 2006, Pages 193-197

https://doi.org/10.1016/j.jep.2006.05.019 Get rights and content

Abstract

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.

Introduction

Uncaria rhynchophylla (Rubiaceae) is widely used in traditional Chinese medicine. The hooks with stem of Uncaria rhynchophylla are known to have anti-hypertensive, anti-epileptic, and neuroprotective activities (Zhu, 1998, Zhang et al., 2004). Moreover, several alkaloid compounds have been isolated from Uncaria rhynchophylla, such as, rhynchophylline, isorhynchophylline, hirstuine, and hirsuteine. These alkaloids have been reported to mainly act on the cardiovascular and central nervous systems, which supports traditional knowledge (Shimada et al., 1999). Shi et al. (2003) reported that rhynchophylline reduces spontaneous motor activity and enhances the sedative and hypnotic effects of sodium pentobarbital in mice. In addition, it was reported that the 70% ethanol extract of the stems of Uncaria rhynchophylla exhibited strong binding to 5-HT₁, 5-HT_1A, GABA_A or GABA_B receptors in vitro (Zhu et al., 1996). These observations encouraged us to study the effects of Uncaria rhynchophylla on anxiety.

The purpose of the present study was to characterize the putative anxiolytic-like activity of the aqueous extract of Uncaria rhynchophylla (AEUR). The anxiolytic and myorelaxant effects of this plant extract were examined, respectively, using the elevated plus-maze (EPM) and a horizontal wire test in rats, and a hole-board apparatus was also used to assess anxiolytic-like effects in mice.

Section snippets

Materials

Buspirone, WAY 100635, and flumazenil were obtained from the Sigma Chemical Co. (USA). Hooks with stem of Uncaria rhynchophylla were obtained from an herbalist supplier in Seoul, and voucher specimens (KHUOPS2001-14) were deposited at the herbarium in the College of Pharmacy, Kyung Hee University (Seoul). The material obtained was authenticated at the Laboratory of Pharmacognosy, Department of Oriental Pharmaceutical Science, College of Pharmacy, Kyung Hee University. All other materials were

Effect of AEUR on locomotor activity

To determine whether a possible stimulatory effect of AEUR modified exploratory behavior, we performed a spontaneous locomotor activity test. However, AEUR (200 mg/kg) produced no significant changes in total ambulatory distances (2485.6 ± 51.9 cm versus 2350.7 ± 114.9 cm) or rearing frequencies (28.4 ± 2.7 versus 24.3 ± 3.0) versus the saline control group.

Effect of a single AEUR treatment on elevated plus-maze performance

The behavioral effects of AEUR or buspirone on rat behavior in the elevated plus-maze are summarized in Table 1. A single AEUR treatment produced an

Discussion

The main findings of this study are that AEUR treatment significantly increases the time spent in the open arms and the frequency of open arm entries in the EPM test, and that these effects were antagonized by WAY 100635, thus demonstrating serotonergic nervous system involvement. In addition, no changes in spontaneous locomotor activities or myorelaxant effects were observed. Therefore, we suggest that AEUR has an anxiolytic-like effect due to 5-HT_1A receptor activation, no obvious adverse

Acknowledgements

This research was supported by a grant (PF0320601-00) from Plant Diversity Research Center of 21st Century Frontier Research Program funded by Ministry of Science and Technology of Korean government. The authors gratefully acknowledge Professor Chang Soo Yook for identifying the plant material.

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Antidepressive mechanisms of rhynchophylline in mice with chronic unpredictable stress-induced depression
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Uncaria rhynchophylla ([Mi] Jack) (gouteng) exerts antidepressive effects. Rhynchophylline (RH), a major component of U. rhynchophylla, exerts similar pharmacological effects to those of gouteng. Thus, RH may have antidepressive effects.
To investigate the anti-depressive effects of RH in chronic unpredictable mild stress (CUMS)-induced depressive mice. The anti-depressive mechanism of RH determined by measuring the 5-HT levels, the expressions of cAMP-response element binding protein (CREB) and brain-derived neurotrophic factor (BDNF) in cortex and hippocampus.
The behaviors of CUMS-induced depressive mice were measured using an open field test (OFT), forced swimming test (FST), and tail suspension test (TST). 5-HT levels were measured using an ELISA kits. The expressions of BDNF and CREB were determined using western blot test.
RH increased the frequency of rearing and grooming in the OFT and decreased the immobility time in the FST and TST. RH effectively increased the 5-HT level and BDNF and CREB expressions in the cortex and hippocampus.
Our findings indicate that the antidepressive mechanism of RH is related to increased levels of 5-HT from regulating CREB and BDNF expressions in cortex and hippocampus.
Recent research progress of Uncaria spp. based on alkaloids: phytochemistry, pharmacology and structural chemistry
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Citation Excerpt :
In fact, the effects of Uncaria spp. on neurotransmitter, mainly around NE, 5-TH and MT receptors, has been partially confirmed in the above-mentioned depression models and cerebral ischemia rat models. In addition, significant binding activity to adrenergic receptors, 5-HT, DA and γ-aminobutyric acid (GABA) receptors of aqueous extracts of U. rhynchophylla displayed anxiolytic effects [122]. The NE concentrations in spinal cord of normal rats were decreased and which in the brain stem were increased at the dose of 20 mg/kg of rhynchophylline (1.2.1), but in the hypothalamus, cortex, amygdala, spinal cord and brain stem were decreased at the dose of 40 mg/kg.
Medicinal plants are well-known in affording clinically useful agents, with rich medicinal values by combining with disease targets through various mechanisms. Plant secondary metabolites as lead compounds lay the foundation for the discovery and development of new drugs in disease treatment. Genus Uncaria from Rubiaceae family is a significant plant source of active alkaloids, with anti-hypertensive, sedative, anti-Alzheimer’s disease, anti-drug addiction and anti-inflammatory effects. This review summarizes and discuss the research progress of Uncaria based on alkaloids in the past 15 years, mainly in the past 5 years, including biosynthesis, phytochemistry, pharmacology and structural chemistry. Among, focusing on representative compounds rhynchophylline and isorhynchophylline, the pharmacological activities surrounding the central nervous system and cardiovascular system are described in detail. On the basis of case studies, this article provides a brief overview of the synthesis and analogues of representative compounds types. In summary, this review provides an early basis for further searching for new targets and activities, discussing the mechanisms of pharmacological activity and studying the structure-activity relationships of active molecules.
Anxiolytic effect of an extract of Salvia miltiorrhiza Bunge (Danshen) in mice
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Salvia miltiorrhiza Bunge (Danshen), a traditional Chinese medicine, has demonstrated in modern studies for its pharmacological activities in treatments of CNS disorders like insomnia, dysphoria. However, its application on anxiolytic effect from the ethanol extract of Salvia miltiorrhiza Bunge (SM_EtOH) has not yet been reported.
This study investigated the anxiolytic effect of the SM_EtOH using the elevated plus-maze test (EPM) and the hole-board test (HBT) with diazepam and buspirone as positive controls. Also, the spontaneous locomotor activity of mice had been investigated in the open field. Further, we have illustrated the anxiolytic mechanisms of SM_EtOH with its influencing upon GABAergic and/or serotonergic nervous systems via a method that SM_EtOH was co-administered with flumazenil, a benzodiazepine (BZD) antagonist, or a drug (WAY-100635), a selective 5HT_1A receptor antagonist.
In hole-board test, results presented that SM_EtOH increased head-dip counts and duration time. On the other hand, a decrease in spontaneous locomotor activity was observed. In the EPM test, SM_EtOH increased the percentage of open-arm entries and the percentage of time spent in open arms. However, when SM_EtOH co-administered with flumazenil or WAY-100635, the anxiolytic effect of SM_EtOH was significantly counteracted.
From these results, we can conclude that the anxiolytic mechanism of SM_EtOH is exerted through an activation of the BZD and 5HT_1A receptors.
Uncaria rhynchophylla (Miq.) Jacks
2020, Naturally Occurring Chemicals against Alzheimer’s Disease
Uncaria rhynchophylla (Miq.) Jacks (Rubiaceae) is a of component of the Chinese crude drug Gou-teng, which is widely used as a remedy for several ailments including cerebrovascular diseases, hypertension, eclampsia, and epilepsy. In chapter, we review the phytochemistry and pharmacological attributes of U. rhynchophylla, with a focus on the neuroprotective activity of the plant. The plant is reported to exert antioxidant, antiinflammatory, antihypertensive, antiarrhythmic, anticancer, anticonvulsive, and neuroprotective properties, which are related to the presence of various classes of bioactive compounds, predominantly indole alkaloids such as rhynchophylline and isorhynchophylline. In vitro and in vivo studies have provided strong evidence that the bioactive compounds present in U. rhynchophylla may potentially be useful in treating neuronal disorders through different modes of action. For instance, with respect to Alzheimer’s disease, constituents of the plant have been showed to play significant roles in inhibiting acetylcholinesterase, Aβ aggregation, counteracting oxidative stress and neuroinflammation, and increasing neuronal survival and synaptic plasticity. This chapter advocates for further investigations into U. rhynchophylla as a novel source of therapeutic agents to prevent and/or manage Alzheimer’s disease.
Validation of UHPLC-MS/MS methods for the determination of kaempferol and its metabolite 4-hydroxyphenyl acetic acid, and application to in vitro blood-brain barrier and intestinal drug permeability studies
2016, Journal of Pharmaceutical and Biomedical Analysis
Citation Excerpt :
Flavonoids reportedly possess a broad spectrum of pharmacological activities, such as anti-inflammatory, antiallergic, neuroprotective, cardioprotective, and cancer chemopreventive properties [1,4–9]. Sedative and anxiolytic-like activities of flavonoid-containing medicinal plants [10–14] and of selected purified flavonoids [15–19] have been substantiated in pharmacological studies. However, the route of administration appeared to be decisive, given that widely occurring flavonols such as kaempferol (KMF) and quercetin induced anxiolytic activities in mice only after oral administration (p.o.), but not upon intraperitoneal (i.p.) application [10].
Sedative and anxiolytic-like properties of flavonoids such as kaempferol and quercetin, and of some of their intestinal metabolites, have been demonstrated in pharmacological studies. However, routes of administration were shown to be critical for observing in vivo activity. Therefore, the ability to cross intestinal and blood-brain barriers was assessed in cell-based models for kaempferol (KMF), and for the major intestinal metabolite of KMF, 4-hydroxyphenylacetic acid (4-HPAA). Intestinal transport studies were performed with Caco-2 cells, and blood-brain barrier transport studies with an immortalized monoculture human model and a primary triple-co-culture rat model. UHPLC–MS/MS methods for KMF and 4-HPAA in Ringer-HEPES buffer and in Hank’s balanced salt solution were validated according to industry guidelines. For all methods, calibration curves were fitted by least-squares quadratic regression with 1/X² as weighing factor, and mean coefficients of determination (R²) were >0.99. Data obtained with all barrier models showed high intestinal and blood-brain barrier permeation of KMF, and no permeability of 4-HPAA, when compared to barrier integrity markers.
Effects of rhynchophylline on GluN1 and GluN2B expressions in primary cultured hippocampal neurons
2014, Fitoterapia
Citation Excerpt :
NMDAR antagonist such as MK-801 shows an anxiolytic effect in several animal models [5–7]. As an antagonist of NMDAR [8], rhynchophylline (Fig. 1) is an important active component of the tetracyclic oxindole alkaloids separated from the Uncaria species whose aqueous extract has an anxiolytic effect [9]. Rhynchophylline reverses the increased glutamic acid and decreased γ-aminobutyric acid levels to control levels in the brain [10] and inhibits GluN2B expression in several nerve nuclei in rats of amphetamine-induced conditioned place preference [11].
N-methyl-d-aspartate (NMDA) receptor subunits GluN1 and GluN2B in hippocampal neurons play key roles in anxiety. Our previous studies show that rhynchophylline, an active component of the Uncaria species, down-regulates GluN2B expression in the hippocampal CA1 area of amphetamine-induced rat. The effects of rhynchophylline on expressions of GluN1 and GluN2B in primary hippocampal neurons in neonatal rats in vitro were investigated. Neonatal hippocampal neurons were cultured with neurobasal-A medium. After incubation for 6 h or 48 h with rhynchophylline (non-competitive NMDAR antagonist) and MK-801 (non-competitive NMDAR antagonist with anxiolytic effect, as the control drug) from day 6, neuron toxicity, mRNA and protein expressions of GluN1 and GluN2B were analyzed. GluN1 is mainly distributed on neuronal axons and dendritic trunks, cytoplasm and cell membrane near axons and dendrites. GluN2B is mainly distributed on the membrane, dendrites, and axon membranes. GluN1 and GluN2B are codistributed on dendritic trunks and dendritic spines. After 48 h incubation, a lower concentration of rhynchophylline (lower than 400 μmol/L) and MK-801 (lower than 200 μmol/L) have no toxicity on neonatal hippocampal neurons. Rhynchophylline up-regulated GluN1 mRNA expression at 6 h and mRNA and protein expressions at 48 h, but down-regulated GluN2B mRNA and protein expressions at 48 h. However, GluN1 and GluN2B mRNA expressions were down-regulated at 6 h, and mRNA and protein expressions were both up-regulated by MK-801 at 48 h. These findings show that rhynchophylline reciprocally regulates GluN1 and GluN2B expressions in hippocampal neurons, indicating a potential anxiolytic property for rhynchophylline.

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¹: Present address: Department of Herbal Medicinal Resource, College of Health and Welfare, Daegu Haany University, Gyeongsan 712-715, Republic of Korea.

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Journal of Ethnopharmacology

Abstract

Introduction

Section snippets

Materials

Effect of AEUR on locomotor activity

Effect of a single AEUR treatment on elevated plus-maze performance

Discussion

Acknowledgements

References (15)

Perinatal asphyxia, hyperthermia and hyperferremia as factors inducing behavioural disturbances in adulthood: a rat model

Behavioural Brain Research

Use of the elevated plus maze in the search for novel anxiolytic agents

Trends in Pharmacological Sciences

5,7-Dihydroxy-6-methoxyflavone, a benzodiazepine site ligand isolated from Scutellaria baicalensis Georgi, with selective antagonistic properties

Biochemical Pharmacology

Anxiolytic effect of wogonin, a benzodiazepine receptor ligand isolated from Scutellaria baicalensis Georgi

Biochemical Pharmacology

Anxiolytic-like effects of extracts from Albizzia julibrissin bark in the elevated plus-maze in rats

Life Sciences

Suppressive effects of isorhynchophylline on 5-HT_2A receptor function in the brain: behavioural and electrophysiological studies

European Journal of Pharmacology

Validation of open:closed arm entries in an elevated plus-maze as a measure of anxiety in the rat

Journal of Neuroscience Methods

Cited by (47)

Antidepressive mechanisms of rhynchophylline in mice with chronic unpredictable stress-induced depression

Recent research progress of Uncaria spp. based on alkaloids: phytochemistry, pharmacology and structural chemistry

Anxiolytic effect of an extract of Salvia miltiorrhiza Bunge (Danshen) in mice

Uncaria rhynchophylla (Miq.) Jacks

Validation of UHPLC-MS/MS methods for the determination of kaempferol and its metabolite 4-hydroxyphenyl acetic acid, and application to in vitro blood-brain barrier and intestinal drug permeability studies

Effects of rhynchophylline on GluN1 and GluN2B expressions in primary cultured hippocampal neurons