Prevention of ginsenoside-induced desensitization of Ca2+-activated Cl- current by microinjection of inositol hexakisphosphate in Xenopus laevis oocytes: involvement of GRK2 and beta-arrestin I

Dissecting the structural features of β-arrestins as multifunctional proteins

β-arrestins bind active G protein-coupled receptors (GPCRs) and play a crucial role in receptor desensitization and internalization. The classical paradigm of arrestin function has been expanded with the identification of many non-receptor-binding partners, which indicated the multifunctional role of β-arrestins in cellular functions. To elucidate the molecular mechanism of β-arrestin-mediated signaling, the structural features of β-arrestins were investigated using X-ray crystallography and cryogenic electron microscopy (cryo-EM). However, the intrinsic conformational flexibility of β-arrestins hampers the elucidation of structural interactions between β-arrestins and their binding partners using conventional structure determination tools. Therefore, structural information obtained using complementary structure analysis techniques would be necessary in combination with X-ray crystallography and cryo-EM data. In this review, we describe how β-arrestins interact with their binding partners from a structural point of view, as elucidated by both traditional methods (X-ray crystallography and cryo-EM) and complementary structure analysis techniques.

Ginsenoside Rb1 pretreatment reverses hippocampal changes in BDNF/TrkB mRNA and protein in rats subjected to acute immobilization stress

Purpose

Episodes of acute emotional or physical stress can have significant adverse effects on the hippocampus. Ginsenoside Rb1, the most predominant ginsenoside present in Panax species, has been reported to show a neuroprotective effect. The purpose of this study was to investigate the influence of ginsenoside Rb1 on plasma corticosterone (CORT) and adrenocorticotropic hormone (ACTH) levels and hippocampal brain-derived neurotrophic factor (BDNF) and tyrosine kinase B (TrkB) levels in rats subjected to acute immobilization stress.

Methods

Wistar rats were divided into controls treated with saline only (N), rats exposed to stress only (M), and rats pretreated with Rb1 (40 mg.kg (−1)) thirty minutes prior to stress exposure (R). In the model, animals were restrained in a plastic immobilizer for 2 h of acute immobilization stress at room temperature. ELISA was used to determine plasma levels of CORT and ACTH. The effect of Rb1 pretreatment on the expression of BDNF and TrkB was determined by immunofluorescence, real-time PCR, and Western blotting analysis.

Results

The R group showed significantly increased plasma CORT and ACTH levels compared to the N and M groups. Acute stress stimulation suppressed BDNF and TrkB protein and mRNA expression in the hippocampus; otherwise, Rb1 pretreatment reversed the decreases.

Conclusion

The results from this study demonstrate that Rb1 pretreatment reverses the decreases in hippocampal BDNF/TrkB and increases the plasma levels of CORT and ACTH, indicating a potential neuroprotective effect of Rb1 against acute stress.

Therapeutic potential of Panax ginseng and its constituents, ginsenosides and gintonin, in neurological and neurodegenerative disorders: a patent review

INTRODUCTION

Ginseng, Panax ginseng, has been used for various diseases and proven its great efficacy in managing central nervous system diseases.

AREAS COVERED

This article covers the therapeutic potential of patents on ginseng and its active constituents to develop therapies for neurodegenerative and neurological disorders, since 2010. The literature review was provided using multiple search engines including Google Patent, Espacenet and US Patent in the field of neurodegenerative diseases, Alzheimer's disease, Parkinson's disease, cognitive, and neurological disorders.

EXPERT OPINION

The gathered data represented outstanding merits of ginseng in treatment of neurodegenerative and neurological disorders. These effects have been mediated by neurogenesis, anti-apoptotic and antioxidant properties, inhibition of mitochondrial dysfunction, receptor-operated Ca²⁺ channels, amyloid beta aggregation, and microglial activation as well as neurotransmitters modulation. However, these compounds have limited clinical application of for the prevention or treatment of neurodegenerative and neurological disorders. This might be due to incomplete data on their clinical pharmacokinetic and toxicity properties, and limited economic investments. There is an increasing trend in use of herbal medicines instead of chemical drugs, so it is time to make more attention to the application of ginseng, the grandfather of medicinal plants, from basic sciences to patients' bed.

Pharmacological and medical applications of Panax ginseng and ginsenosides: a review for use in cardiovascular diseases

Panax ginseng, also called Asian or Korean ginseng, has long been traditionally used in Korea and China to treat various diseases. The major active ingredients of P. ginseng are ginsenosides, which have been shown to have a variety of therapeutic effects, including antioxidation, anti-inflammatory, vasorelaxation, antiallergic, antidiabetic, and anticancer. To date, approximately 40 ginsenoside components have been reported. Current research is concentrating on using a single ginseng compound, one of the ginsenosides, instead of the total ginseng compounds, to determine the mechanisms of ginseng and ginsenosides. Recent in vitro and in vivo results show that ginseng has beneficial effects on cardiac and vascular diseases through efficacy, including antioxidation, control of vasomotor function, modulation of ion channels and signal transduction, improvement of lipid profiles, adjustment of blood pressure, improvement in cardiac function, and reduction in platelet adhesion. This review aims to provide valuable information on the traditional uses of ginseng and ginsenosides, their therapeutic applications in animal models and humans, and the pharmacological action of ginseng and ginsenosides.

Ginseng pharmacology: a new paradigm based on gintonin-lysophosphatidic acid receptor interactions

Ginseng, the root of Panax ginseng, is used as a traditional medicine. Despite the long history of the use of ginseng, there is no specific scientific or clinical rationale for ginseng pharmacology besides its application as a general tonic. The ambiguous description of ginseng pharmacology might be due to the absence of a predominant active ingredient that represents ginseng pharmacology. Recent studies show that ginseng abundantly contains lysophosphatidic acids (LPAs), which are phospholipid-derived growth factor with diverse biological functions including those claimed to be exhibited by ginseng. LPAs in ginseng form a complex with ginseng proteins, which can bind and deliver LPA to its cognate receptors with a high affinity. As a first messenger, gintonin produces second messenger Ca²⁺ via G protein-coupled LPA receptors. Ca²⁺ is an intracellular mediator of gintonin and initiates a cascade of amplifications for further intercellular communications by activation of Ca²⁺-dependent kinases, receptors, gliotransmitter, and neurotransmitter release. Ginsenosides, which have been regarded as primary ingredients of ginseng, cannot elicit intracellular [Ca²⁺]_i transients, since they lack specific cell surface receptor. However, ginsenosides exhibit non-specific ion channel and receptor regulations. This is the key characteristic that distinguishes gintonin from ginsenosides. Although the current discourse on ginseng pharmacology is focused on ginsenosides, gintonin can definitely provide a mode of action for ginseng pharmacology that ginsenosides cannot. This review article introduces a novel concept of ginseng ligand-LPA receptor interaction and proposes to establish a paradigm that shifts the focus from ginsenosides to gintonin as a major ingredient representing ginseng pharmacology.

Yin and Yang of ginseng pharmacology: ginsenosides vs gintonin

Ginseng, the root of Panax ginseng, has been used in traditional Chinese medicine as a tonic herb that provides many beneficial effects. Pharmacologic studies in the last decades have shown that ginsenosides (ginseng saponins) are primarily responsible for the actions of ginseng. However, the effects of ginseng are not fully explained by ginsenosides. Recently, another class of active ingredients called gintonin was identified. Gintonin is a complex of glycosylated ginseng proteins containing lysophosphatidic acids (LPAs) that are the intracellular lipid mitogenic mediator. Gintonin specifically and potently activates the G protein-coupled receptors (GPCRs) for LPA. Thus, the actions of ginseng are now also linked to LPA and its GPCRs. This linkage opens new dimensions for ginseng pharmacology and LPA therapeutics. In the present review, we evaluate the pharmacology of ginseng with the traditional viewpoint of Yin and Yang components. Furthermore, we will compare ginsenoside and gintonin based on the modern view of molecular pharmacology in terms of ion channels and GPCRs.

A simple method for the preparation of crude gintonin from ginseng root, stem, and leaf

Ginseng has been used as a general tonic agent to invigorate the human body as an adaptogenic agent. In a previous report, we have shown that ginseng contains a novel glycolipoprotein called gintonin. The main function of gintonin is to transiently enhance intracellular free Ca²⁺ [Ca²⁺]_i levels in animal cells. The previous method for gintonin isolation included multiple steps using organic solvents. In the present report, we developed a simple method for the preparation of crude gintonin from ginseng root as well as stem and leaf, which produced a higher yield of gintonin than the previous one. The yield of gintonin was 0.20%, 0.29%, and 0.81% from ginseng root, stem, and leaf, respectively. The apparent molecular weight of gintonin isolated from stem and leaf through sodium dodecyl sulfate polyacrylamide gel electrophoresis was almost same as that from root but the compositions of amino acids, carbohydrates or lipids differed slightly between them. We also examined the effects of crude gintonin from ginseng root, stem, and leaf on endogenous Ca²⁺-activated Cl- channel (CaCC) activity of Xenopus oocytes through mobilization of [Ca²⁺]_i. We found that the order of potency for the activation of CaCC was ginseng root > stem > leaf. The ED₅₀ was 1.4±1.4, 4.5±5.9, and 3.9±1.1 μg/mL for root, stem and leaf, respectively. In the present study, we demonstrated for the first time that in addition to ginseng root, ginseng stem and leaf also contain gintonin. Gintonin can be prepared from a simple method with higher yield of gintonin from ginseng root, stem, and leaf. Finally, these results demonstrate the possibility that ginseng stem and leaf could also be utilized for ginstonin preparation after a simple procedure, rather than being discarded.

An edible gintonin preparation from ginseng

Ginseng, the root of Panax ginseng, is one of the oldest herbal medicines. It has a variety of physiological and pharmacological effects. Recently, we isolated a subset of glycolipoproteins that we designated gintonin, and demonstrated that it induced transient change in intracellular calcium concentration ([Ca²⁺]_i) in cells via G-protein-coupled receptor signaling pathway(s). The previous method for gintonin isolation included multiple steps using methanol, butanol, and other organic solvents. In the present study, we developed a much simple method for the preparation of gintonin from ginseng root using 80% ethanol extraction. The extracted fraction was designated edible gintonin. This method produced a high yield of gintonin (0.20%). The chemical characteristics of gintonin such as molecular weight and the composition of the extract product were almost identical as the gintonin prepared using the previous extraction regimen involving various organic solvents. We also examined the physiological effects of edible gintonin on endogenous Ca²⁺-activated Cl^- channel activity of Xenopus oocytes. The 50% effective dose was 1.03±0.3 μg/mL. Finally, since gintonin preparation through ethanol extraction is easily reproducible, gintonin could be commercially applied for ginseng-derived functional health food and/or drug following the confirmations of in vitro and in vivo physiological and pharmacological effects of gintonin.

Gintonin, newly identified compounds from ginseng, is novel lysophosphatidic acids-protein complexes and activates G protein-coupled lysophosphatidic acid receptors with high affinity

Recently, we isolated a subset of glycolipoproteins from Panax ginseng, that we designated gintonin, and demonstrated that it induced [Ca2+]i transients in cells via G protein-coupled receptor (GPCR) signaling pathway(s). However, active components responsible for Ca2+ mobilization and the corresponding receptor(s) were unknown. Active component(s) for [Ca2+]i transients of gintonin were analyzed by liquid chromatography-electrospray ionization-tandem mass spectrometry and ion-mobility mass spectrometry, respectively. The corresponding receptor(s)were investigated through gene expression assays. We found that gintonin contains LPA C18:2 and other LPAs. Proteomic analysis showed that ginseng major latex-like protein and ribonuclease-like storage proteins are protein components of gintonin. Gintonin induced [Ca2+]i transients in B103 rat neuroblastoma cells transfected with human LPA receptors with high affinity in order of LPA2 >LPA5 > LPA1 > LPA3 > LPA4. The LPA1/LPA3 receptor antagonist Ki16425 blocked gintonin action in cells expressing LPA1 or LPA3. Mutations of binding sites in the LPA3 receptor attenuated gintonin action. Gintonin acted via pertussis toxin (PTX)-sensitive and -insensitive G protein-phospholipase C (PLC)-inositol 1,4,5-trisphosphate (IP3)-Ca2+ pathways. However, gintonin had no effects on other receptors examined. In human umbilical vein endothelial cells (HUVECs) gintonin stimulated cell proliferation and migration. Gintonin stimulated ERK1/2 phosphorylation. PTX blocked gintonin-mediated migration and ERK1/2 phosphorylation. In PC12 cells gintonin induced morphological changes, which were blocked by Rho kinase inhibitorY-27632. Gintonin contains GPCR ligand LPAs in complexes with ginseng proteins and could be useful in the development of drugs targeting LPA receptors.

Antidepressant effects of ginseng total saponins in the forced swimming test and chronic mild stress models of depression

Ginseng total saponins (GTS) are the major active components of Panax ginseng C.A. Meyer, which has been used as a popular tonic herb for 2000 years in Far East countries. In the present study, two classic animal models: the forced swimming test (FST) and the chronic mild stress (CMS) model were used to evaluate the antidepressant-like activities of GTS. It was observed that GTS at doses of 50 and 100 mg/kg significantly reduced the immobility time in the FST in mice after 7-day treatment. GTS also reversed the reduction in the sucrose preference index, decrease in locomotor activity as well as prolongation of latency of feeding in the novelty environment displayed by CMS rats. In addition, HPLC-ECD and immunohistochemical staining analysis indicated that the CMS-induced decrease in monoamine neurotransmitter concentration and brain-derived neurotrophic factor (BDNF) expression in the hippocampus were almost completely reversed by GTS. In conclusion, GTS exerts antidepressant-like effects in two highly specific and predictive animal models of depression. The activity of GTS in antidepression may be mediated partly through enhancing the monoamine neurotransmitter concentration and BDNF expression in the hippocampus.

Ginseng compounds: an update on their molecular mechanisms and medical applications

Ginseng is one of the most widely used herbal medicines and is reported to have a wide range of therapeutic and pharmacological applications. Ginsenosides, the major pharmacologically active ingredients of ginseng, appear to be responsible for most of the activities of ginseng including vasorelaxation, antioxidation, anti-inflammation and anti-cancer. Approximately 40 ginsenoside compounds have been identified. Researchers now focus on using purified individual ginsenoside to reveal the specific mechanism of functions of ginseng instead of using whole ginseng root extracts. Individual ginsenosides may have different effects in pharmacology and mechanisms due to their different chemical structures. Among them the most commonly studied ginsenosides are Rb1, Rg1, Rg3, Re, Rd and Rh1. The molecular mechanisms and medical applications of ginsenosides have attracted much attention and hundreds of papers have been published in the last few years. The general purpose of this update is to provide information of recently described effects of ginsenosides on antioxidation, vascular system, signal transduction pathways and interaction with receptors. Their therapeutic applications in animal models and humans as well as the pharmacokinetics and toxicity of ginsenosides are also discussed in this review. This review concludes with some thoughts for future directions in the further development of ginseng compounds as effective therapeutic agents.

Ginseng compounds: an update on their molecular mechanisms and medical applications

Ginseng is one of the most widely used herbal medicines and is reported to have a wide range of therapeutic and pharmacological applications. Ginsenosides, the major pharmacologically active ingredients of ginseng, appear to be responsible for most of the activities of ginseng including vasorelaxation, antioxidation, anti-inflammation and anti-cancer. Approximately 40 ginsenoside compounds have been identified. Researchers now focus on using purified individual ginsenoside to reveal the specific mechanism of functions of ginseng instead of using whole ginseng root extracts. Individual ginsenosides may have different effects in pharmacology and mechanisms due to their different chemical structures. Among them the most commonly studied ginsenosides are Rb1, Rg1, Rg3, Re, Rd and Rh1. The molecular mechanisms and medical applications of ginsenosides have attracted much attention and hundreds of papers have been published in the last few years. The general purpose of this update is to provide information of recently described effects of ginsenosides on antioxidation, vascular system, signal transduction pathways and interaction with receptors. Their therapeutic applications in animal models and humans as well as the pharmacokinetics and toxicity of ginsenosides are also discussed in this review. This review concludes with some thoughts for future directions in the further development of ginseng compounds as effective therapeutic agents.

Ginsenosides: are any of them candidates for drugs acting on the central nervous system?

The last two decades have shown a marked expansion in the number of publications regarding the effects of Panax ginseng. Ginsenosides, which are unique saponins isolated from Panax ginseng, are the pharmacologically active ingredients in ginseng, responsible for its effects on the central nervous system (CNS) and the peripheral nervous system. Recent studies have shown that ginsenosides regulate various types of ion channels, such as voltage-dependent and ligand-gated ion channels, in neuronal and heterologously expressed cells. Ginsenosides inhibit voltage-dependent Ca(2+), K(+), and Na(+) channel activities in a stereospecific manner. Ginsenosides also inhibit ligand-gated ion channels such as N-methyl-d-aspartate, some subtypes of nicotinic acetylcholine, and 5-hydroxytryptamine type 3 receptors. Competition and site-directed mutagenesis experiments revealed that ginsenosides interact with ligand-binding sites or channel pore sites and inhibit open states of ion channels. This review will introduce recent findings and advances on ginsenoside-induced regulation of ion channel activities in the CNS, and will further expand the possibilities that ginsenosides may be useful and potentially therapeutic choices in the treatment of neurodegenerative disorders.

Ginsenoside Rg1 protects neurons from hypoxic-ischemic injury possibly by inhibiting Ca2+ influx through NMDA receptors and L-type voltage-dependent Ca2+ channels

The purpose of this study is to assess the neuroprotective effect of Rg1, a ginsenoside. We measured cell viability and lactate dehydrogenase (LDH) release from primary culture of rat hippocampal neurons and electrical activities in hippocampal slices of rats, before and after the neurons were deprived of oxygen and glucose. In addition, cerebral damage was evaluated with magnetic resonance imaging after middle cerebral artery was occluded transiently. Nissl staining was used for histological observation and immunohistochemistry analysis for activated caspase-3 expression of the brain. Furthermore, calcium influx was measured with laser confocal microscopy in neurons perfused with KCl (50 mM) or N-methyl-d-aspartate (NMDA, 1 mM), or deprived of oxygen and glucose. The influences of ginsenoside Rg1 on these parameters were determined simultaneously. We found that treatment of Rg1: 1) increased the neuronal viability; 2) promoted the recovery of electrical activity in hippocampal slices; 3) reduced the release of LDH, cerebral damage area, neuronal loss and expression of caspase-3; and 4) inhibited calcium influx induced by NMDA, KCl or oxygen/glucose deprivation. However, the protective effect of Rg1 was blocked by mifepristone, an antagonist of glucocorticoid receptors. Taken together, these results suggest that ginsenoside Rg1 can reduce neuronal death, including apoptotic cell death, induced by hypoxic-ischemic insults. This neuroprotective effect is probably mediated by the activation of glucocorticoid receptors, and by the inhibition of calcium influx through NMDA receptors and L-type voltage-dependent Ca2+ channels and the resultant reduction of intracellular free Ca2+.

Ginsenoside Rb1 promotes neurotransmitter release by modulating phosphorylation of synapsins through a cAMP-dependent protein kinase pathway

Ginseng, the root of Panax ginseng C.A. Meyer (Araliaceae), has been extensively used in traditional oriental medicine for the prevention and treatment of aging-related disorders for over 2000 years. Accumulating evidence suggests that ginsenosides such as Rg1 and Rb1, which are the pharmacologically active ingredients of ginseng, modulate neurotransmission. Synapsins are abundant phosphoproteins essential for regulating neurotransmitter release. All synapsins contain a short amino-terminal domain A that is highly conserved and phosphorylated by cAMP-dependent protein kinase (PKA), which plays a key role in regulating neurotransmitter release. In the present study, we demonstrated that both Rg1 and Rb1 increased neurotransmitter release in undifferentiated and differentiated PC12 cells. However, in the presence of the PKA inhibitor H89, Rg1, but not Rb1, still induced neurotransmitter release. Moreover, Rb1, but not Rg1, enhanced the phosphorylation of synapsins via PKA pathway. In summary, Rb1 promotes neurotransmitter release by increasing the phosphorylation of synapsins through the PKA pathway, whereas the similar effects observed with Rg1 are independent of the phosphorylation of synapsins.

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Nonvisual arrestin oligomerization and cellular localization are regulated by inositol hexakisphosphate binding

Interactions between arrestins and phosphoinositides have been reported to regulate multiple membrane-associated signaling and trafficking events including clathrin-mediated endocytosis and light adaptation in Drosophila. Arrestins have been proposed to have nuclear and cytosolic functions as well, although the ligand dependence of these functions has not been investigated. Here we characterize the structural, molecular, and cellular interactions between arrestin-2 and inositol hexakisphosphate (inositol 1,2,3,4,5,6-hexakisphosphate (IP(6))). The crystal structure of the arrestin-2.IP(6) complex was solved to 2.9 A with crystal lattice contacts suggesting two sites on a protein monomer mediating IP(6) binding. Mutagenesis coupled to isothermal titration calorimetry and tritiated IP(6) binding assays confirmed two-site binding with a low affinity IP(6)-binding site in the N-domain and a high affinity site in the C-domain. Native gel electrophoresis, gel filtration, and analytical ultracentrifugation demonstrated the ability of IP(6) to promote arrestin-2 oligomerization via the two crystallographically defined ligand-binding locations. In addition, analysis in mammalian cells revealed that arrestin-2 not only undergoes homo-oligomerization, but it can also hetero-oligomerize with arrestin-3 in a manner that depends on IP(6)-binding sites. Mutation of either IP(6)-binding site in arrestin-2 disrupted oligomerization while interactions with known binding partners including clathrin, AP-2, and ERK2 were maintained. Subcellular localization studies showed that arrestin-2 oligomers are primarily cytoplasmic, whereas arrestin-2 monomers displayed increased nuclear localization. Thus, by promoting cytosolic oligomerization, IP(6) binding is proposed to be a negative regulator of interactions of arrestin with plasma membrane and nuclear signaling proteins.

Effect of calmodulin on ginseng saponin-induced Ca2+-Activated CI-channel activation inXenopus laevis oocytes

We previously demonstrated the ability of ginseng saponins (active ingredients of Panax ginseng) to enhance Ca2+-activated Cl- current. The mechanism for this ginseng saponin-induced enhancement was proposed to be the release of Ca2+ from IP3-sensitive intracellular stores through the activation of PTX-insensitive Galpha(q/11) proteins and PLC pathway. Recent studies have shown that calmodulin (CaM) regulates IP3 receptor-mediated Ca2+ release in both Ca2+-dependent and -independent manner. In the present study, we have investigated the effects of CaM on ginseng saponin-induced Ca2+-activated Cl- current responses in Xenopus oocytes. Intraoocyte injection of CaM inhibited ginseng saponin-induced Ca2+-activated Cl- current enhancement, whereas co-injection of calmidazolium, a CaM antagonist, with CaM blocked CaM action. The inhibitory effect of CaM on ginseng saponin-induced Ca2+-activated Cl- current enhancement was dose- and time-dependent, with an IC50 of 14.9 +/- 3.5 microM. The inhibitory effect of CaM on saponin's activity was maximal after 6 h of intraoocyte injection of CaM, and after 48 h the activity of saponin recovered to control level. The half-recovery time was calculated to be 16.7 +/- 4.3 h. Intraoocyte injection of CaM inhibited Ca2+-induced Ca2+-activated Cl- current enhancement and also attenuated IP3-induced Ca2+-activated Cl- current enhancement. Ca2+/CaM kinase II inhibitor did not inhibit CaM-caused attenuation of ginseng saponin-induced Ca2+-activated Cl- current enhancement. These results suggest that CaM regulates ginseng saponin effect on Ca2+-activated Cl current enhancement via Ca2+-independent manner.

Inhibitory influence of ginsenoside Rb3 on activation of strychnine-sensitive glycine receptors in hippocampal neurons of rat

Whole-cell patch-clamp technique was used to investigate the effect of ginsenoside Rb(3) (Rb(3)), an active constituent of Panax ginseng, on glycine receptor activity in immature hippocampal neurons, which were dissociated acutely from hippocampal CA(1) area in Sprague-Dawley rats aging 10-14 days using the method of enzyme digestion with mechanical dissociation. As a result, glycine elicited an inward current (I(gly)) in a concentration-dependent manner in approximately 86% of those isolated neurons tested. This current was strychnine-sensitive. Rb(3) itself did not elicit any membrane currents. However, coapplication of Rb(3) inhibited peak current of I(gly). This depressant effect of Rb(3) varied with its concentrations. At a concentration of 0.1 micromol/L, ginsenoside Rb(3) had the most significant inhibition, with a net reduction of 31% in average. Moreover, the inhibition of I(gly) by Rb(3) did not depend on the membrane potential. Rb(3) (0.1 micromol/L) presented inhibitory effect on I(gly) mainly at higher glycine concentrations (>100 micromol/L), and decreased maximal glycine efficacy. This effect was the same as that of a non-competitive antagonist of glycine receptors. Finally, we found that Rb(3) prolonged the time constant of activation of I(gly). It is therefore suggested that ginsenoside Rb(3), possibly as a non-competitive antagonist, could inhibit strychnine-sensitive glycine current at a dose-dependent manner in acutely dissociated hippocampal CA(1) neurons of young rats, and decrease of affinity of glycine to receptors and delay of receptor activation may be involved in this inhibition. Inhibitory effect of ginsenoside Rb(3) on I(gly) is possibly one of the bases of many pharmacological actions of Panax ginseng.