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

Plants with Anti-Addictive Potential

Drug addiction is prevalent among individuals of modern society, being a major cause of disability and premature loss of life. Although the drug addiction have profound social, economical and health impact in the world population, its management remains a challenge as available pharmacological treatments remains ineffective for most people. The limited efficacy and adverse effects have led to a search for alternative therapies to treat drug addiction. In this context, natural products are an important source for new chemical substances with a potential therapeutic applicability. Therefore, this chapter will present data obtained after an extensive literature search regarding the use of medicinal plants as a pharmacological alternative for drug addiction treatment.

Antimania-Like Effect of Panax ginseng Regulating the Glutamatergic Neurotransmission in REM-Sleep Deprivation Rats

Previous studies have shown the therapeutic properties of ginseng and ginsenosides on hyperactive and impulsive behaviors in several psychiatric diseases. Herein, we investigated the effect of Panax ginseng Meyer (PG) on hyperactive/impulsive behaviors in a manic-like animal model, sleep deprivation (SD) rats. Male rats were sleep-deprived for 48 h, and PG (200 mg/kg) was administered for 4 days, from 2 days prior to the start of SD to the end date of SD. The elevated plus maze (EPM) test showed that PG alleviated the increased frequency of entries into and spent time within open arms by SD. In order to investigate the molecular mechanism on this effect of PG, we assessed differentially expressed genes (DEGs) in the prefrontal cortex of PG-treated SD rats using RNA sequencing (RNA-seq) and performed gene-enrichment analysis for DEGs. The gene-enrichment analysis showed that PG most prominently affected the glutamatergic synapse pathway. Among the glutamatergic synapse pathway genes, particularly, PG enhanced the expressions of glutamate transporter Slc1a3 and Slc1a2 reduced in SD rats. Moreover, we found that PG could inhibit the SD-induced phosphorylation of the NR2A subunit of the NMDA receptor. These results suggested that PG might have a therapeutic effect against the manic-like behaviors, regulating the glutamatergic neurotransmission.

Dopamine D1 receptor antagonist reduces stimulant-induced conditioned place preferences and dopamine receptor supersensitivity

Repeated administration of stimulants induces conditioned place preference (CPP). Dopamine receptor supersensitivity is developed in stimulant-induced CPP animals; however, dopamine receptor subtypes associated with the development of supersensitivity in CPP animals are largely unknown. The present preclinical study aimed to examine whether dopamine D1 or D2 receptor antagonists exert inhibitory effects on stimulant-induced psychological behaviors. Additionally, the authors aimed to elucidate the role of dopamine receptor supersensitivity on the development of reward-related behavior. Sprague Dawley rats subjected to methamphetamine- and cocaine-induced CPP tests were treated with dopamine D1 (SCH23390) or D2 (sulpiride) receptor antagonists. Following the CPP experiment, rats were challenged with apomorphine (dopamine receptor agonist), and locomotor activity was measured. Methamphetamine- and cocaine-induced CPP was reduced with the administration of SCH23390, but not sulpiride. In addition, the apomorphine challenge evoked an increase in locomotor activity in stimulant-pre-treated rats, reflecting dopamine receptor supersensitivity. SCH23390 pre-treatment inhibited the development of dopamine receptor supersensitivity, while sulpiride demonstrated no inhibitory effects. These results suggest that the dopamine D1 receptor antagonist SCH23390 inhibits the development of dopamine receptor supersensitivity which is associated with the development of CPP.

Limonene Inhibits Methamphetamine-Induced Sensitizations via the Regulation of Dopamine Receptor Supersensitivity

Limonene is a cyclic terpene found in citrus essential oils and inhibits methamphetamine-induced locomotor activity. Drug dependence is a severe neuropsychiatric condition that depends in part on changes in neurotransmission and neuroadaptation, induced by exposure to recreational drugs such as morphine and methamphetamine. In this study, we investigated the effects of limonene on the psychological dependence induced by drug abuse. The development of sensitization, dopamine receptor supersensitivity, and conditioned place preferences in rats was measured following administration of limonene (10 or 20 mg/kg) and methamphetamine (1 mg/kg) for 4 days. Limonene inhibits methamphetamine-induced sensitization to locomotor activity. Expression of dopamine receptor supersensitivity induced by apomorphine, a dopamine receptor agonist, was significantly reduced in limonenepretreated rats. However, there was no significant difference in methamphetamine-induced conditioned place preferences between the limonene and control groups. These results suggest that limonene may ameliorate drug addiction-related behaviors by regulating postsynaptic dopamine receptor supersensitivity.

Dependence potential of propofol: behavioral pharmacology in rodents

Propofol is an anesthetic commonly used to provide sedation or to induce and maintain an anesthetic stated. However, there are reports which indicate propofol may cause psychological dependence or be abused. In the present study, we used various behavioral tests including climbing test, jumping test, conditioned place preference, and self-administration test to assess the dependence potential and abuse liability of propofol compared to a positive control (methamphetamine) or a negative control (saline or intralipid). Among the tests, the conditioned place preference test was conducted with a biased method, and the selfadministration test was performed under a fixed ratio (FR) 1 schedule, 1 h per session. No difference was found in the climbing test and jumping test, but propofol (30 mg/kg, i.p.) increased the rewarding effect in the conditioned place preference test, and it showed a positive reinforcing effect compared to the vehicle. These results indicate that propofol tends to show psychological dependence rather than physical dependence, and it seems not to be related with dopaminergic system.

Effects of a Rhodiola rosea L. extract on acquisition and expression of morphine tolerance and dependence in mice

This study investigated the effect of Rhodiola rosea L. extract on acquisition and expression of morphine tolerance and dependence in mice. Therefore animals were injected with repeated administration of morphine (10 mg/kg, subcutaneous) twice daily for five or six days, in order to make them tolerant or dependent. Rhodiola rosea L. extract (0, 10, 15 and 20 mg/kg) was administered by the intragastric route 60 min prior to each morphine injection (for acquisition) or prior the last injection of morphine or naloxone on test day (for tolerance or dependence expression, respectively). Morphine tolerance was evaluated by testing its analgesic effect in the tail flick test at the 1st and 5th days. Morphine dependence was evaluated by counting the number of withdrawal signs (jumping, rearing, forepaw tremor, teeth chatter) after naloxone injection (5 mg/kg; intraperitoneal) on the test day (day 6). Results showed that Rhodiola rosea L. extract significantly reduced the expression of morphine tolerance, while it was ineffective in modulating its acquisition. Conversely, Rhodiola rosea L. extract significantly and dose-dependently attenuated both development and expression of morphine dependence after chronic or acute administration. These data suggest that Rhodiola rosea L. may have human therapeutic potential for treatment of opioid addiction.

Inhibitory effects of ginseng total saponin on up-regulation of cAMP pathway induced by repeated administration of morphine

We have reported that ginseng total saponin (GTS) inhibited the development of physical and psychological dependence on morphine. However, the possible molecular mechanisms of GTS are unclear. Therefore, this study was undertaken to understand the possible molecular mechanism of GTS on the inhibitory effects of morphine-induced dependence. It has been reported that the up-regulated cAMP pathway in the LC of the mouse brain after repeated administration of morphine contributes to the feature of withdrawals. GTS inhibited up-regulation of cAMP pathway in the LC after repeated administration of morphine in this experiment. GTS inhibited cAMP levels and protein expression of protein kinase A (PKA). In addition, GTS inhibited the increase of cAMP response element binding protein (CREB) phosphorylation. Therefore, we conclude that the inhibitory effects of GTS on morphine-induced dependence might be mediated by the inhibition of cAMP pathway.

Measuring reward with the conditioned place preference (CPP) paradigm: update of the last decade

Conditioned place preference (CPP) continues to be one of the most popular models to study the motivational effects of drugs and non-drug treatments in experimental animals. This is obvious from a steady year-to-year increase in the number of publications reporting the use this model. Since the compilation of the preceding review in 1998, more than 1000 new studies using place conditioning have been published, and the aim of the present review is to provide an overview of these recent publications. There are a number of trends and developments that are obvious in the literature of the last decade. First, as more and more knockout and transgenic animals become available, place conditioning is increasingly used to assess the motivational effects of drugs or non-drug rewards in genetically modified animals. Second, there is a still small but growing literature on the use of place conditioning to study the motivational aspects of pain, a field of pre-clinical research that has so far received little attention, because of the lack of appropriate animal models. Third, place conditioning continues to be widely used to study tolerance and sensitization to the rewarding effects of drugs induced by pre-treatment regimens. Fourth, extinction/reinstatement procedures in place conditioning are becoming increasingly popular. This interesting approach is thought to model certain aspects of relapse to addictive behavior and has previously almost exclusively been studied in drug self-administration paradigms. It has now also become established in the place conditioning literature and provides an additional and technically easy approach to this important phenomenon. The enormous number of studies to be covered in this review prevented in-depth discussion of many methodological, pharmacological or neurobiological aspects; to a large extent, the presentation of data had to be limited to a short and condensed summary of the most relevant findings.

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.

Biological activities and distribution of plant saponins

Plant saponins are widely distributed amongst plants and have a wide range of biological properties. The more recent investigations and findings into their biological activities were summarized. Isolation studies of saponins were examined to determine which are the more commonly studied plant families and in which families saponins have been identified.

Alcoholic extract of 'Bacopa monniera' reduces the in vitro effects of morphine withdrawal in guinea-pig ileum

The effect of the alcoholic extract of the whole plant of Bacopa monniera (Scrophulariaceae) on morphine withdrawal was evaluated in vitro in guinea-pig ileum. After a 4 min in vitro exposure to morphine, addition of naloxone induced a strong contraction. Addition of various concentrations of the alcoholic extract of B. monniera (100-1000 microg/ml) 15 min before exposure to morphine reduced the naloxone-induced contraction in a dose-dependent manner. The results suggest that B. monniera extract may be useful in reducing the withdrawal symptoms induced by morphine.

[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.

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.

Inhibitory effects of velvet antler water extract on morphine-induced conditioned place preference and DA receptor supersensitivity in mice

The repeated administration of morphine in mice produced conditioned place preference (CPP) and postsynaptic dopamine (DA) receptor supersensitivity. 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 nonpreferred 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. The oral administration of velvet antler water extract (VAWE) from Cerrus elaphus, prior to the morphine treatment in mice inhibited the development of morphine-induced CPP and postsynaptic DA receptor supersensitivity. These results suggest that the inhibitory effects of VAWE on morphine-induced CPP may be closely related to the recovery of dysfunction in the dopaminergic system produced by morphine because both phenomena were inhibited by VAWE. But a single administration of VAWE did not inhibit apomorphine-induced climbing behavior, indicating that antidopaminergic activity was not produced by a single administration of VAWE at the postsynaptic DA receptors. From the above results, it is presumed that VAWE may be useful for prevention and therapy of the adverse actions of morphine.

Panax ginseng blocks morphine-induced thymic apoptosis by lowering plasma corticosterone level

The effects of Panax ginseng on morphine-induced immune suppression were studied. Morphine (20 mg/kg, SC, 4 days) decreased body weight increment rate and caused atrophy of thymus and spleen. These changes were partly reversed by concomitant administration of ginseng total saponin (GTS, 100 mg/kg, oral, 9 days). Morphine elevated the serum corticosterone level and caused the DNA fragmentation of thymocytes. These sequential events were completely blocked by a concomitant administration of GTS. Flow cytometry analysis showed that GTS specifically blocked morphine-induced apoptosis of thymocytes.

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.

Measuring reward with the conditioned place preference paradigm: a comprehensive review of drug effects, recent progress and new issues

This review gives an overview of recent findings and developments in research on brain mechanisms of reward and reinforcement from studies using the place preference conditioning paradigm, with emphasis on those studies that have been published within the last decade. Methodological issues of the paradigm (such as design of the conditioning apparatus, biased vs unbiased conditioning, state dependency effects) are discussed. Results from studies using systemic and local (intracranial) drug administration, natural reinforcers, and non-drug treatments and from studies examining the effects of lesions are presented. Papers reporting on conditioned place aversion (CPA) experiments are also included. A special emphasis is put on the issue of tolerance and sensitization to the rewarding properties of drugs. Transmitter systems that have been investigated with respect to their involvement in brain reward mechanisms include dopamine, opioids, acetylcholine, GABA, serotonin, glutamate, substance P, and cholecystokinin, the motivational significance of which has been examined either directly, by using respective agonist or antagonist drugs, or indirectly, by studying the effects of these drugs on the reward induced by other drugs. For a number of these transmitters, detailed studies have been conducted to delineate the receptor subtype(s) responsible for the mediation of the observed drug effects, particularly in the case of dopamine, the opioids, serotonin and glutamate. Brain sites that have been implicated in the mediation of drug-induced place conditioning include the 'traditional' brain reward sites, ventral tegmental area and nucleus accumbens, but the medial prefrontal cortex, ventral pallidum, amygdala and the pedunculopontine tegmental nucleus have also been shown to play important roles in the mediation of place conditioning induced by drugs or natural reinforcers. Thus, although the paradigm has also been criticized because of some inherent methodological problems, it is clear that during the past decade place preference conditioning has become a valuable and firmly established and very widely used tool in behavioural pharmacology and addiction research.

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.