Blockade by ginseng total saponin of the development of methamphetamine reverse tolerance and dopamine receptor supersensitivity in mice

Natural Products in Modulating Methamphetamine-Induced Neuronal Apoptosis

Methamphetamine (METH), an amphetamine-type psychostimulant, is highly abused worldwide. Chronic abuse of METH causes neurodegenerative changes in central dopaminergic neurons with numerous neuropsychiatric consequences. Neuronal apoptosis plays a critical role in METH-induced neurotoxicity and may provide promising pharmacological targets for preventing and treating METH addiction. In recent years, accumulating evidence has revealed that natural products may possess significant potentials to inhibit METH-evoked neuronal apoptosis. In this review, we summarized and analyzed the improvement effect of natural products on METH-induced neuronal apoptosis and their potential molecular mechanisms on modulating dopamine release, oxidative stress, mitochondrial-dependent apoptotic pathway, endoplasmic reticulum stress-mediated apoptotic pathway, and neuroinflammation. Hopefully, this review may highlight the potential value of natural products in modulating METH-caused neuronal apoptosis and provide useful information for future research and developments of novel and efficacious pharmacotherapies in this field.

Inhibitory effects of ginseng total saponins on hypoxia-induced dysfunction and injuries of cultured astrocytes

The effects of ginseng total saponins (GTS) on hypoxic damage of primary cultures of astrocytes were studied. Hypoxia was created by placing cultures in an air tight chamber that was flushed with 95% N(2)/5% CO(2) for 15 min before being sealed. Cultures showed evidence of significant cell injury after 24 h of hypoxia (increased lactate dehydrogenase (LDH) content in the culture medium, cell swelling and decreased glutamate uptake and protein content). Addition of GTS (0.1, 0.3 mg/ml) to the cultures during the exposure to hypoxic conditions produced dose-dependent inhibition of the LDH efflux. GTS (0.1, 0.3 mg/ml) also produced significant inhibition of the increased cell volume of astrocytes measured by [(3)H]O-methyl-D-glucose uptake under the hypoxic conditions. Decreased glutamate uptake and protein content was inhibited by GTS. These data suggest that GTS prevents astrocytic cell injury induced by severe hypoxiain vitro.

Inhibitory effects of paeonol on morphine-induced locomotor sensitization and conditioned place preference in mice

The inhibitory effects of paeonol, a major compound of Paeoniae radix, on the development of locomotor sensitization, conditioned place preference (CPP) and dopamine receptor supersensitivity induced by the repeated administration of morphine were investigated through behavioral experiments. A single administration of morphine produces hyperlocomotion. Repeated administration of morphine develops sensitization (reverse tolerance), a progressive enhancement of locomotion, which is used as a model for studying the drug-induced drug-seeking behaviors, and CPP, which is used as a model for studying drug reinforcement. Paeonol inhibited morphine-induced hyperlocomotion, sensitization and CPP. In addition, paeonol inhibited the development of postsynaptic dopamine receptors supersensitivity, which may be an underlying common mechanism that mediates the morphine-induced dopaminergic behaviors such as sensitization and CPP. Apomorphine (a dopamine agonist)-induced climbing behaviors also were inhibited by a single direct administration of paeonol. These results provide evidence that paeonol exerts anti-dopaminergic activity, and it is suggested that paeonol may be useful for the prevention and therapy of these adverse actions of morphine.

Pharmacological action of Panax ginseng on the behavioral toxicities induced by psychotropic agents

Morphine-induced analgesia has been shown to be antagonized by ginseng total saponins (GTS), which also inhibit the development of analgesic tolerance to and physical dependence on morphine. GTS is involved in both of these processes by inhibiting morphine-6-dehydrogenase, which catalyzes the synthesis of morphinone from morphine, and by increasing the level of hepatic glutathione, which participates in the toxicity response. Thus, the dual actions of ginseng are associated with the detoxification of morphine. In addition, the inhibitory or facilitated effects of GTS on electrically evoked contractions in guinea pig ileum (mu-receptors) and mouse vas deferens (delta-receptors) are not mediated through opioid receptors, suggesting the involvement of non-opioid mechanisms. GTS also attenuates hyperactivity, reverse tolerance (behavioral sensitization), and conditioned place preference induced by psychotropic agents, such as methamphetamine, cocaine, and morphine. These effects of GTS may be attributed to complex pharmacological actions between dopamine receptors and a serotonergic/adenosine A2A/ delta-opioid receptor complex. Ginsenosides also attenuate the morphine-induced cAMP signaling pathway. Together, the results suggest that GTS may be useful in the prevention and therapy of the behavioral side effects induced by psychotropic agents.

Anxiolytic-like effects of ginseng in the elevated plus-maze model: comparison of red ginseng and sun ginseng

This study was performed to investigate the anxiolytic-like effects of red ginseng (RG, steamed raw ginseng at 98-100 degrees C) and sun ginseng (SG, heat-processed ginseng at higher temperature) in mice using the elevated plus-maze model. Furthermore, the anxiolytic-like effects of RG and SG were compared to a known active anxiolytic drug (diazepam). The RG butanol fraction (100 mg/kg) significantly increased the number of open arms entries and the time spent on the open arm (indicators of anxiolytic-like effects) compared with that of the saline group. However, lower doses of the SG total extract (50 mg/kg) and the SG butanol fraction (25 and 50 mg/kg) significantly increased the number of open arms entries and the time spent on the open arms. The RG total extract (100 mg/kg) and the SG total extract at a lower dose (25 mg/kg) did not increase the number of open arm entries or the time spent on the open arm. On the other hand, the RG butanol fraction (100 mg/kg), the SG total extract (50 mg/kg), and the SG butanol fraction (50 mg/kg) decreased locomotor activity in a manner similar to diazepam. These data indicate that ginseng has anxiolytic-like effects, and the anxiolytic potential of SG is stronger than that of RG in the elevated plus-maze model. Ginseng saponins have been suggested to play an important role in the anxiolytic effects of ginseng. We provide evidence that ginseng may be useful for the treatment of anxiety.

Ginsenosides attenuate methamphetamine-induced behavioral side effects in mice via activation of adenosine A2A receptors: possible involvements of the striatal reduction in AP-1 DNA binding activity and proenkephalin gene expression

Current evidence suggests that ginsenosides inhibit methamphetamine (MA)-induced changes in behavior, but the precise mechanisms that underlie this effect are yet to be determined. We examined the role of adenosine receptors in the ginsenoside-induced changes in hyperlocomotion and conditioned place preference (CPP) in mice that occurred in response to administration of MA (2 mg/kg, i.p. x 1 or 2 mg/kg, i.p. x 6). Changes in circling behavior paralleled changes in CPP in the presence of MA. Pre-treatment with ginsenosides (50 or 150 mg/kg, i.p.) attenuated the MA-induced circling behavior and CPP. This attenuation was reversed by the adenosine A2A receptor antagonist 1,3,7-trimethyl-8-(3-chrostyryl)xanthine (CSC; 0.5 and 1.0 mg/kg) in a dose-dependent manner, but neither the adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dimethylxanthine (CPT; 0.5 and 1.0 mg/kg) nor the A2B receptor antagonist alloxazine (ALX; 1.5 and 3.0 mg/kg) had any such effect. MA-induced increases in activator protein (AP)-1 DNA binding activity, Fos-related antigen immunoreactivity (FRA-IR), proenkephalin mRNA expression, and proenkephalin-like immunoreactivity were reduced consistently in the striatum of animals that were pretreated with ginsenosides. These reductions were largely prevented by CSC, but not by CPT or ALX. Our results suggest that the stimulation of A2A receptors by ginsenosides attenuates the changes in behavior and the increases in AP-1 DNA binding activity, FRA-IR, and proenkephalin gene expression in mouse striatum that are induced by MA.

[Pharmacological and physiological effects of ginseng on actions induced by opioids and psychostimulants]

Pharmacological and physiological effects of ginseng on actions induced by opioids and psychostimulants were summarized. Analgesic effects of opioids, such as morphine and U-50,488H, were blocked by ginseng in a non-opioid dependent manner. Furthermore, ginseng inhibited the tolerance to and dependence on morphine, and prevented the suppressive effect on the development of morphine tolerance caused by co-exposure to foot-shock stress, but not psychological stress. On the other hand, behavioral sensitization (reverse tolerance to ambulation-accelerating effect) to morphine, methamphetamine (MAP) and cocaine was also inhibited by ginseng. Interestingly, ginseng also inhibited the appearance of the recurrent phenomenon (reappearance of the sensitized state was observed at the time of readministration of MAP and cocaine even after a 30-day discontinuation of drug administration) of the effect of MAP and cocaine. The conditioned place preference of MAP and cocaine was completely blocked by ginseng. These findings provide evidence that ginseng may be useful clinically for the prevention of abuse and dependence of opioids and psychostimulants.

Hydroalcoholic extract and fractions of Davilla rugosa Poiret: effects on spontaneous motor activity and elevated plus-maze behavior

Davilla rugosa Poiret is commonly used in Brazilian folk medicine. The use as stimulant induced us to study the effects on motor activity and anxiety using an open-field and an elevated plus-maze, respectively. The hydroalcoholic extract of the stems (HE) was fractionated with chloroform (CF), chloroform/ethyl acetate (CAF), ethyl acetate (AF), ethyl acetate/ethanol (AEF), ethanol (EF) and ethanol/water (EWF). Rats were treated orally with HE (7.5, 15, 30 or 60 mg/kg) or fractions (15 mg/kg). In the open-field, HE (15 mg/kg), AEF, EF and EWF increased locomotion frequency and decreased immobility time; the contrary was observed with 30 and 60 mg/kg of HE. These doses also increased defecation. No effects were observed with 7.5 mg/kg of HE, CF, CAF or AF, except for an increase in defecation induced by AF. In the elevated plus-maze, total entries and number of entries into the open and closed arms and the time spent in the open arms and its percentage were increased only with 15 mg/kg of HE. The open-field results suggest that the drug increases motor activity (stimulant effect) and that the active components are in the three more polar fractions. An anxiolytic effect was observed only with the HE.

Inhibitory effects of ginseng total saponin on nicotine-induced hyperactivity, reverse tolerance and dopamine receptor supersensitivity

A single administration of a low dose of nicotine produced hyperactivity in mice. A repeated administration of nicotine developed reverse tolerance to the ambulation-accelerating activity of nicotine and also developed postsynaptic dopamine (DA) receptor supersensitivity. The development of reverse tolerance was evidenced by an increased ambulatory response to nicotine, and the development of postsynaptic DA receptor supersensitivity was evidenced by the enhanced response in ambulatory activity to apomorphine, a DA receptor agonist. Administration of ginseng total saponin (GTS) prior to and during the nicotine treatment in mice inhibited not only nicotine-induced hyperactivity and reverse tolerance, but also postsynaptic DA receptor supersensitivity in nicotine-induced reverse tolerant mice. These results suggest that inhibition by GTS of nicotine-induced hyperactivity and reverse tolerance may be closely related with the inhibition of the dopaminergic activation induced by nicotine and that the development of nicotine-induced reverse tolerance may be associated with enhanced DA receptor sensitivity.

Effects of ginsenosides on bovine adrenal tyrosine hydroxylase

The present study was undertaken to investigate the effects of ginsenosides on bovine adrenal tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine biosynthesis. Ginsenoside-Rb1, Rc, Re and Rg, inhibited the TH activity by 51.5, 25.4, 31.3, 44.3 and 43.3%, respectively, at a concentration of 80 microg/ml. Ginsenoside-Rb1, Rc, Re and Rg1 exhibited noncompetitive inhibition of TH activity with a substrate L-tyrosine. From these results, it is presumed that the effects of ginsenosides on TH activity observed in vitro might be also produced in vivo, and thereby the inhibitory effects of ginsenosides on TH activity may be partially responsible for the antidopaminergic action of ginsenosides by reducing the availability of dopamine at the presynaptic dopamine receptor in vivo.

Effect of ginseng total saponin on bovine adrenal tyrosine hydroxylase

Ginseng total saponin (GTS) can modulate dopaminergic activity at both presynaptic and postsynaptic dopamine receptors (Kim et al., 1998). The present study investigated the effect of GTS on the bovine adrenal tyrosine hydroxylase (TH), which catalyze L/tyrosine to DOP. GTS inhibited the bovine adrenal TH by 42.4, 51.5 and 55.3% at concentrations of 40, 80 and 100 micrograms/ml, respectively. The IC50 value of GTS was 77.5 micrograms/ml. GTS exhibited noncompetitive inhibition with a substrate L-tyrosine. The Ki value was 155 micrograms/ml.

Effects of ginsenosides on Ca2+ channels and membrane capacitance in rat adrenal chromaffin cells

We investigated the effects of ginseng total saponins (GTS) and five ginsenosides on voltage-dependent Ca2+ channels and membrane capacitance using rat adrenal chromaffin cells. In this study, cells were voltage-clamped in a whole-cell recording mode and a perforated patch-clamp technique was used. The inward Ca2+ currents (I(Ca)) was elicited by depolarization and the change in cell membrane capacitance (deltaCm) was monitored. The application of GTS (100 microg/ml) induced rapid and reversible inhibition of the Ca2+ current by 38.8 +/- 3.6% (n = 16). To identify the particular single component that seems to be responsible for Ca2+ current inhibition, the effects of five ginsenosides (ginsenoside Rb1, Rc, Re, Rf, and Rg1) on the Ca2+ current were examined. The inhibitions to the Ca2+ current by Rb1, Rc, Re, Rf, and Rg1 were 15.3 +/- 2.2% (n = 5); 36.9 +/- 2.4% (n = 7); 28.1 +/- 1.9% (n = 12); 19.0 +/- 2.5% (n = 10); and 16.3 +/- 1.6% (n = 15), respectively. The order of inhibitory potency (100 microM) was Rc > Re > Rf > Rg1 > Rb1. A software based phase detector technique was used to monitor membrane capacitance change (deltaCm). The application of GTS (100 microg/ml) induced inhibitory effects on deltaCm by 60.8 +/- 9.7% (n = 10). The inhibitions of membrane capacitance by Rb1, Rc, Re, Rf, and Rg1 were 35.3 +/- 5.5% (n = 7); 41.8 +/- 7.0% (n = 8); 40.5 +/- 5.9% (n = 9); 51.2 +/- 7.6% (n = 9); and 35.9 +/- 5.1% (n = 10), respectively. The inhibitory potencies of the ginsenosides on deltaCm were Rf > Rc > Re > Rg1 > Rb1. Therefore, we found that GTS and ginsenosides exerted inhibitory effects on both Ca2+ currents and deltaCm in rat adrenal chromaffin cells. These results suggest that ginseng saponins regulate catecholamine secretion from adrenal chromaffin cells and this regulation could be the cellular basis of antistress effects induced by ginseng.

Inhibition by ginsenosides Rb1 and Rg1 of methamphetamine-induced hyperactivity, conditioned place preference and postsynaptic dopamine receptor supersensitivity in mice

The ginsenosides Rb1 and Rg1, the major components of ginseng saponin, inhibited not only methamphetamine-induced hyperactivity but also conditioned place preference (CPP) in mice following a single or repeated administration. Dopamine (DA) receptor supersensitivity, which developed in methamphetamine-induced CPP mice, was also inhibited by both Rb1 and Rg1. Therefore, the present results suggest that Rb1 and Rg1 may be the active components of ginseng saponin in the modulation of methamphetamine-induced dopaminergic behaviors such as hyperactivity and CPP, supporting our previous conclusion that ginseng saponin might modulate methamphetamine-induced dysfunction at both the pre- and postsynaptic DA receptors.

Effects of the ginsenosides Rg1 and Rb1 on morphine-induced hyperactivity and reinforcement in mice

Recent studies have demonstrated that ginseng saponin inhibits the hyperactivity and conditioned place-preference response induced by psychostimulants and opiates. This seems to occur by direct or indirect modulation of dopaminergic activity. However, it is not known which components of ginseng saponin are active. These experiments were conducted to determine the effects of the ginsenosides Rb1 and Rg1, major components of the protopanaxadiol and protopanaxatriol fractions of ginseng saponin, on morphine-induced hyperactivity and conditioned place-preference. Morphine-induced hyperactivity, but not apomorphine-induced climbing behaviour, was inhibited by both Rb1 and Rg1. These findings confirm the hypothesis that ginsenosides modulate catecholaminergic activity preferentially at pre-synaptic sites. Morphine-induced conditioned place-preference was inhibited by Rg1, but not by Rb1. It has previously been shown that at low doses Rb1 and Rg1 are equally effective at inhibition of catecholamine secretion at the pre-synaptic site, but that at high doses Rg1 is a more effective inhibitor. This observation might explain our finding that morphine-induced conditioned place-preference was inhibited by Rg1 only. Our findings suggest that Rg1, a component of ginseng saponin with appropriate activity, might be a useful agent for prevention and treatment of the adverse effects of morphine.

Effects of ginseng total saponin on morphine-induced hyperactivity and conditioned place preference in mice

A single or repeated administration of morphine in mice produced hyperactivity, conditioned place preference (CPP) and postsynaptic dopamine (DA) receptor supersensitivity. The hyperactivity induced by morphine was evidenced by measuring the enhanced ambulatory activity using a tilting-type ambulometer. CPP effects were evaluated assessing the increased time spent by the mice to morphine and the inhibition of CPP by the decreased time spent by the mice in the white compartment. Postsynaptic DA receptor supersensitivity in mice displaying a morphine-induced CPP was evidenced by the enhanced response in ambulatory activity to the DA agonist, apomorphine (2 mg/kg, s.c.). The intraperitoneal injection of ginseng total saponin (GTS) from the root of Panax ginseng C.A. Meyer (Araliaceae), prior to and during the morphine treatment in mice inhibited morphine-induced hyperactivity and CPP. GTS inhibited the development of postsynaptic DA receptor supersensitivity. A single dose administration of GTS also inhibited apomorphine-induced climbing behavior, showing the antidopaminergic action of GTS at the postsynaptic DA receptor. These results suggest that the development of morphine-induced CPP may be associated with the enhanced DA receptor sensitivity and that GTS inhibition of the morphine-induced hyperactivity and CPP may be closely related with the inhibition of dopaminergic activation induced by morphine.

MK-801 inhibits methamphetamine-induced conditioned place preference and behavioral sensitization to apomorphine in mice

Intraperitoneal administration of MK-801 (0.1 mg/ kg), an N-methyl-D-aspartate (NMDA) receptor antagonist, before and during methamphetamine treatment inhibited methamphetamine-induced conditioned place preference (CPP) in mice. Behavioral sensitization to a dopamine (DA) receptor agonist apomorphine that developed in methamphetamine-induced CPP mice was also inhibited by MK-801. Furthermore, MK-801 inhibited apomorphine-induced postsynaptic dopaminergic action, cage-climbing behavior. Therefore, the present studies suggest that methamphetamine-induced behaviors, such as CPP and behavioral sensitization, may be closely related to the dopaminergic activation mediated via the NMDA receptor. The behavioral sensitization to apomorphine may be a possible underlying mechanism of methamphetamine-induced CPP, because behavioral sensitization developed in methamphetamine-induced CPP mice, as well as apomorphine-induced climbing behavior in mice, were inhibited by MK-801.

Blockade by ginseng total saponin of methamphetamine-induced hyperactivity and conditioned place preference in mice

Ginseng total saponin (GTS) inhibited methamphetamine-induced hyperactivity and conditioned place preference (CPP). Dopamine (DA) receptor supersensitivity was developed in methamphetamine-induced CPP mice and it was inhibited by GTS. GTS also inhibited apomorphine-induced climbing behavior, showing the antidopaminergic activity of GTS. These results suggest that GTS inhibition of the methamphetamine-induced hyperactivity and CPP may be closely related with the inhibition of dopaminergic activation induced by methamphetamine.