A study of the mechanisms involved in the neurotoxic action of 3,4-methylenedioxymethamphetamine (MDMA, 'ecstasy') on dopamine neurones in mouse brain

Withania somnifera influences MDMA-induced hyperthermic, cognitive, neurotoxic and neuroinflammatory effects in mice

Withania somnifera (WS) is utilized in Ayurvedic medicine owing to its central and peripheral beneficial properties. Several studies have accrued indicating that the recreational amphetamine-related drug (+/-)- 3,4-methylenedioxymethamphetamine (MDMA; Ecstasy) targets the nigrostriatal dopaminergic system in mice, inducing neurodegeneration and gliosis, causing acute hyperthermia and cognitive impairment. This study aimed to investigate the effect of a standardized extract of W. somnifera (WSE) on MDMA-induced neurotoxicity, neuroinflammation, memory impairment and hyperthermia. Mice received a 3-day pretreatment with vehicle or WSE. Thereafter, vehicle- and WSE-pretreated mice were randomly divided into four groups: saline, WSE, MDMA alone, WSE plus MDMA. Body temperature was recorded throughout treatment, and memory performance was assessed by a novel object recognition (NOR) task at the end of treatment. Thereafter, immunohistochemistry was performed to evaluate in the substantia nigra pars compacta (SNc) and striatum the levels of tyrosine hydroxylase (TH), as marker of dopaminergic degeneration, and of glial fibrillary acidic protein (GFAP) and TMEM119, as markers of astrogliosis or microgliosis, respectively. MDMA-treated mice showed a decrease in TH-positive neurons and fibers in the SNc and striatum respectively, an increase in gliosis and body temperature, and a decrease in NOR performance, irrespective of vehicle or WSE pretreatment. Acute WSE plus MDMA counteracted the modifications in TH-positive cells in SNc, GFAP-positive cells in striatum, TMEM in both areas and NOR performance, as compared to MDMA alone, while no differences were observed as compared to saline. Results indicate that WSE acutely administered in combination with MDMA, but not as pretreatment, protects mice against the noxious central effects of MDMA.

Neurotoxicological profile of the hallucinogenic compound 25I-NBOMe

4-Iodo-2,5-dimethoxy-N-(2-methoxybenzyl)phenethylamine (25I-NBOMe) is a new psychoactive substance with strong hallucinogenic properties. Our previous data reported increased release of dopamine, serotonin, and glutamate after acute injections and a tolerance development in the neurotransmitters release and rats’ behavior after chronic treatment with 25I-NBOMe. The recreational use of 25I-NBOMe is associated with severe intoxication and deaths in humans. There is no data about 25I-NBOMe in vivo toxicity towards the brain tissue. In this article 25I-NBOMe-crossing through the blood–brain barrier (BBB), the impact on DNA damage, apoptosis induction, and changes in the number of cortical and hippocampal cells were studied. The presence of 25I-NBOMe in several brain regions shortly after the drug administration and its accumulation after multiple injections was found. The DNA damage was detected 72 h after the chronic treatment. On the contrary, at the same time point apoptotic signal was not identified. A decrease in the number of glial but not in neural cells in the frontal (FC) and medial prefrontal cortex (mPFC) was observed. The obtained data indicate that 25I-NBOMe passes easily across the BBB and accumulates in the brain tissue. Observed oxidative DNA damage may lead to the glial cells’ death.

Neurotoxicity of MDMA: Main effects and mechanisms

Preclinical and clinical studies indicate that 3,4-methylenedioxymethamphetamine (MDMA; 'ecstasy'), in addition to having abuse potential, may elicit acute and persistent abnormalities of varying severity at the central level. Importantly, neurotoxic effects of MDMA have been demonstrated in experimental animals. Accordingly, central toxicity induced by MDMA may pose a serious harm for health, since MDMA is among the substances that are used for recreational purposes by young and adult people. This review provides a concise overview of recent findings from preclinical and clinical studies that evaluated the central effects of MDMA, and the mechanisms involved in the neurotoxicity induced by this amphetamine-related drug.

Activation of Antioxidant and Proteolytic Pathways in the Nigrostriatal Dopaminergic System After 3,4-Methylenedioxymethamphetamine Administration: Sex-Related Differences

3,4-Methylenedioxymethamphetamine (MDMA, “ecstasy”) is an amphetamine-related drug that may damage the dopaminergic nigrostriatal system. To investigate the mechanisms that sustain this toxic effect and ascertain their sex-dependence, we evaluated in the nigrostriatal system of MDMA-treated (4 × 20 mg/kg, 2 h apart) male and female mice the activity of superoxide dismutase (SOD), the gene expression of SOD type 1 and 2, together with SOD1/2 co-localization with tyrosine hydroxylase (TH)-positive neurons. In the same mice and brain areas, activity of glutathione peroxidase (GPx) and of β2/β5 subunits of the ubiquitin-proteasome system (UPS) were also evaluated. After MDMA, SOD1 increased in striatal TH-positive terminals, but not nigral neurons, of males and females, while SOD2 increased in striatal TH-positive terminals and nigral neurons of males only. Moreover, after MDMA, SOD1 gene expression increased in the midbrain of males and females, whereas SOD2 increased only in males. Finally, MDMA increased the SOD activity in the midbrain of females, without affecting GPx activity, decreased the β2/β5 activities in the striatum of males and the β2 activity in the midbrain of females. These results suggest that the mechanisms of MDMA-induced neurotoxic effects are sex-dependent and dopaminergic neurons of males could be more sensitive to SOD2- and UPS-mediated toxic effects.

In utero exposure to dexamethasone causes a persistent and age-dependent exacerbation of the neurotoxic effects and glia activation induced by MDMA in dopaminergic brain regions of C57BL/6J mice

Clinical and preclinical evidence indicates that prenatal exposure to glucocorticoids may induce detrimental effects in the offspring, including reduction in fetal growth and alterations in the CNS. On this basis, the present study investigated whether in utero exposure to high levels of glucocorticoids is a risk factor that may lead to an exacerbation of the central noxious effects induced by psychoactive drugs consumed later in life. To this end, pregnant C57BL6/J dams were treated with dexamethasone (DEX, 0.05 mg/kg per day) from gestational day 14 until delivery. Thereafter, the male offspring were evaluated to ascertain the magnitude of dopaminergic damage, astrogliosis and microgliosis elicited in the nigrostriatal tract by the amphetamine-related drug 3,4--methylenedioxymethamphetamine (MDMA, 4 × 20 mg/kg, 2 h apart, sacrificed 48 h later) administered at either adolescence or adulthood. Immunohistochemistry was performed in the substantia nigra pars compacta (SNc) and striatum, to evaluate dopaminergic degeneration by measuring tyrosine hydroxylase (TH), as well as astrogliosis and microgliosis by measuring glial fibrillary acidic protein (GFAP) and ionized calcium-binding adapter molecule 1 (IBA-1), respectively. Moreover, immunohistochemistry was used to ascertain the co-localization of IBA-1 with either the pro-inflammatory interleukin (IL) IL-1β or the anti-inflammatory IL IL-10, in order to determine the microglial phenotype. In utero administration of DEX induced dopaminergic damage by decreasing the density of TH-positive fibers in the striatum, although only in adult mice. MDMA administration induced dopaminergic damage and glia activation in the nigrostriatal tract of adolescent and adult mice. Mice exposed to DEX in utero and treated with MDMA later in life showed a more pronounced loss of dopaminergic neurons (adolescent mice) and astrogliosis (adolescent and adult mice) in the SNc, compared with control mice. These results suggest that prenatal exposure to glucocorticoids may induce an age-dependent and persistent increase in the susceptibility to central toxicity of amphetamine-related drugs used later in life.

Of mice and men on MDMA: A translational comparison of the neuropsychobiological effects of 3,4-methylenedioxymethamphetamine ('Ecstasy')

MDMA (3,4-methylendioxymethamphetamine), also known as Ecstasy, is a stimulant drug recreationally used by young adults usually in dance clubs and raves. Acute MDMA administration increases serotonin, dopamine and noradrenaline by reversing the action of the monoamine transporters. In this work, we review the studies carried out over the last 30 years on the neuropsychobiological effects of MDMA in humans and mice and summarise the current knowledge. The two species differ with respect to the neurochemical consequences of chronic MDMA, since it preferentially induces serotonergic dysfunction in humans and dopaminergic neurotoxicity in mice. However, MDMA alters brain structure and function and induces hormonal, psychomotor, neurocognitive, psychosocial and psychiatric outcomes in both species, as well as physically damaging and teratogen effects. Pharmacological and genetic studies in mice have increased our knowledge of the neurochemical substrate of the multiple effects of MDMA. Future work in this area may contribute to developing pharmacological treatments for MDMA-related disorders.

Minocycline attenuates 3,4-methylenedioxymethamphetamine-induced hyperthermia in the rat brain

Hyperthermia is most dangerous clinical symptom of acute MDMA administration, and a key factor related to potentially life-threatening MDMA-induced complications. MDMA induces a consistently faster onset of brain hyperthermia when compared to a delayed and moderate hyperthermia in the body, and the most harmful effects of MDMA are related to its modulation of neural functions. The primary focus of this study was to investigate the effects of minocycline, a centrally acting tetracycline derivative on MDMA-induced brain hyperthermia at high ambient temperature. However, we also simultaneously recorded body temperature, heart rate, and locomotor activity changes, allowing us to gain a better understanding of the mechanisms underlying the MDMA-induced hyperthermic response. We also investigated the effects of MDMA at normal ambient temperature to provide further evidence as to the importance of environmental factors on the intensity of MDMA's temperature effects. At normal ambient temperature, MDMA (10 mg/kg, i.p.) induced a significant brain and body hypothermia for the first 90 min following drug administration, and significantly increased heart rate and locomotor activity compared to saline controls. At high ambient temperature however, MDMA (10 mg/kg, i.p.) induced a robust and extended brain and body hyperthermia, as well as significantly increased heart rate and locomotor activity. A 3-day minocycline (50 mg/kg, i.p.) pre-treatment significantly attenuated MDMA-induced increases in brain temperature, body temperature, heart rate, and locomotor activity. Our findings indicate that minocycline is more effective in attenuating the exacerbated MDMA-induced hyperthermic response in the brain compared to the body at high ambient temperature.

Lack of Rhes Increases MDMA-Induced Neuroinflammation and Dopamine Neuron Degeneration: Role of Gender and Age

Ras homolog enriched in striatum (Rhes) is a protein that exerts important physiological functions and modulates psychostimulant drug effects. On this basis, the object of this study was to assess 3,4-methylenedioxymethamphetamine (MDMA) effects on microglial (CD11b) and astroglial (GFAP) activation and on dopamine neuron degeneration (TH) in wild-type (WT) and Rhes knockout (KO) male and female mice of different ages. Motor activity was also evaluated. Adult (3 months) MDMA-treated mice displayed an increase in GFAP-positive cells in striatum (STR), whereas the substantia nigra pars compacta (SNc) was affected only in male mice. In these mice, the increase of CD11b was more extensive including STR, SNc, motor cortex (CTX), ventral tegmental area (VTA), and nucleus accumbens (NAc). MDMA administration also affected TH immunoreactivity in both STR and SNc of male but not female WT and Rhes KO mice. In middle-aged mice (12 months), MDMA administration further increased GFAP and CD11b and decreased TH immunoreactivity in STR and SNc of all mice. Finally, MDMA induced a higher increase of motor activity in adult Rhes KO male, but not female mice. The results show that Rhes protein plays an important role on MDMA-mediated neuroinflammation and neurodegeneration dependent on gender and age, and confirm the important role of Rhes protein in neuroinflammatory and neurodegenerative processes.

Long-term systemic administration with low dose of 3,4-methylenedioxymethamphetamine causes photoreceptor cell damage in CD1 mice

OBJECTIVE

As a powerful psychostimulant with high potential for abuse, 3,4-methylenedioxymethamphetamine (MDMA) causes long-lasting neurotoxicity. This study was to investigate the effects of systemic administration of MDMA on retinal damage in CD1 mice and its underlying mechanisms.

MATERIAL AND METHODS

CD1 mice were randomly divided into two groups (n = 10): group 1 receiving PBS by intraperitoneal injection daily; group 2 receiving 2 mg/kg MDMA by intraperitoneal injection daily for 3 months. The retinal function was tested by electroretinography (ERG). The retinal morphology and histology was evaluated by Toluidine blue staining and TUNEL assay, respectively. Inflammatory cytokines were measured by ELISA assays. Gene and protein expression was detected by real-time PCR and western blot.

RESULTS

Results demonstrated that retinal damage was caused by MDMA after 3-month treatment, evidenced by retinal dysfunction through photoreceptor cell apoptosis induced by inflammatory response and oxidative stress.

CONCLUSION

Our study indicated that systemic administration of MDMA increased inflammatory response in photoreceptor cells to cause retinal dysfunction on CD1 mice, providing the scientific rationale for the photoreceptor cell damage caused by the MDMA abuse.

Repeated Administration of 3,4-Methylenedioxymethamphetamine (MDMA) Elevates the Levels of Neuronal Nitric Oxide Synthase in the Nigrostriatal System: Possible Relevance to Neurotoxicity

Previous studies have consistently demonstrated that the amphetamine-related drug 3,4-methylenedioxymethamphetamine (MDMA) induces dopaminergic damage in the mouse brain, and that this effect is most marked in the nigrostriatal system. Moreover, it has been suggested that the overproduction of nitric oxide (NO) may participate in the dopaminergic damage induced by MDMA. To further elucidate this issue, we evaluated the levels of the enzyme nitric oxide synthase (nNOS), which catalyzes the production of NO, in mice treated with regimens of MDMA that induce progressive and persistent neurotoxicity in the dopaminergic nigrostriatal system. Mice received 14, 28, or 36 administrations of MDMA (10 mg/kg i.p.), twice a day/twice a week, and were sacrificed at different time-points after treatment discontinuation. Thereafter, the number of nNOS-positive neurons was quantified by immunohistochemistry in the caudate-putamen (CPu) and substantia nigra pars compacta (SNc). MDMA elevated the numbers of nNOS-positive neurons in the CPu of mice that received 28 or 36 drug administrations. This effect was still detectable at 3 months after treatment discontinuation. Moreover, MDMA elevated the numbers of nNOS-positive neurons in the SNc. However, this effect occurred only in mice that received 28 drug administrations and were sacrificed 3 days after treatment discontinuation. These results are in line with the hypothesis that activation of the NO cascade participates in the toxic effects induced by MDMA in the dopaminergic nigrostriatal system. Moreover, they suggest that activation of the NO cascade induces toxic effects that are more marked in striatal terminals, compared with nigral neurons.

Neurochemical and Neurotoxic Effects of MDMA (Ecstasy) and Caffeine After Chronic Combined Administration in Mice

MDMA (3,4-methylenedioxymethamphetamine) is a psychostimulant popular as a recreational drug because of its effect on mood and social interactions. MDMA acts at dopamine (DA) transporter (DAT) and serotonin (5-HT) transporter (SERT) and is known to induce damage of dopamine and serotonin neurons. MDMA is often ingested with caffeine. Caffeine as a non-selective adenosine A1/A2A receptor antagonist affects dopaminergic and serotonergic transmissions. The aim of the present study was to determine the changes in DA and 5-HT release in the mouse striatum induced by MDMA and caffeine after their chronic administration. To find out whether caffeine aggravates MDMA neurotoxicity, the content of DA and 5-HT, density of brain DAT and SERT, and oxidative damage of nuclear DNA were determined. Furthermore, the effect of caffeine on MDMA-induced changes in striatal dynorphin and enkephalin and on behavior was assessed. The DA and 5-HT release was determined with in vivo microdialysis, and the monoamine contents were measured by HPLC with electrochemical detection. DNA damage was assayed with the alkaline comet assay. DAT and SERT densities were determined by immunohistochemistry, while prodynorphin (PDYN) and proenkephalin were determined by quantitative PCR reactions. The behavioral changes were measured by the open-field (OF) test and novel object recognition (NOR) test. Caffeine potentiated MDMA-induced DA release while inhibiting 5-HT release in the mouse striatum. Caffeine also exacerbated the oxidative damage of nuclear DNA induced by MDMA but diminished DAT decrease in the striatum and worsened a decrease in SERT density produced by MDMA in the frontal cortex. Neither the striatal PDYN expression, increased by MDMA, nor exploratory and locomotor activities of mice, decreased by MDMA, were affected by caffeine. The exploration of novel object in the NOR test was diminished by MDMA and caffeine. Our data provide evidence that long-term caffeine administration has a powerful influence on functions of dopaminergic and serotonergic neurons in the mouse brain and on neurotoxic effects evoked by MDMA.

Progression and Persistence of Neurotoxicity Induced by MDMA in Dopaminergic Regions of the Mouse Brain and Association with Noradrenergic, GABAergic, and Serotonergic Damage

The amphetamine-related drug 3,4-methylenedioxymethamphetamine (MDMA) is known to induce neurotoxic damage in dopaminergic regions of the mouse brain. In order to characterize how the number of administrations influenced the severity of MDMA-induced dopaminergic damage and to describe the localization and persistence of this damage, we evaluated the changes in tyrosine hydroxylase (TH) and dopamine transporter (DAT) in different regions of the mouse brain. Moreover, we investigated whether dopaminergic damage was associated with noradrenergic, GABAergic, and serotonergic damage, by evaluating the changes in noradrenaline transporter (NET), glutamic acid decarboxylase-67 (GAD-67), and serotonin transporter (SERT). Mice received 14, 28, or 36 MDMA administrations (10 mg/kg twice a week) and were sacrificed at different time points (postnatal days 85, 110, 138, or 214) for immunohistochemical evaluation. Mice receiving 28 administrations showed reduced levels of DAT-positive fibers in caudate-putamen (CPu) and medial prefrontal cortex (mPFC) and reduced levels of TH-positive nigral neurons. These mice also displayed increased NET-positive hippocampal fibers, reduced GAD-67-positive neurons in CPu and hippocampus, and reduced GAD-67-positive fibers in mPFC. Similar effects of MDMA on DAT, TH, and GAD-67 were found in mice receiving 36 administrations, which also displayed reduced levels of striatal, cortical, and hippocampal TH-immunoreactive fibers. The reductions in dopaminergic markers and GAD-67 persisted at 3 months after MDMA discontinuation. Finally, MDMA never modified the levels of SERT. These results provide further insight into the localization and persistence of MDMA-induced dopaminergic damage and show that this effect may associate with GABAergic but not noradrenergic or serotonergic damage.

Behavioral and Stereological Analysis of the Effects of Intermittent Feeding Diet on the Orally Administrated MDMA ("ecstasy") in Mice

Background: 3,4-methylenedioxy-methamphetamine or MDMA (also known as "ecstasy" or "molly") is a commonly abused drug that affects behavior and can lead to neuronal damage. Intermittent feeding is an effective dietary protocol that promotes neuroprotection and improves behavioral outcomes in animal models of neurotoxicity and neurodegenerative diseases. In this study, we investigated the behavioral and histological outcomes of the effect of intermittent feeding on the orally administered MDMA in mice. Methods: The animals (male albino mice) were divided into four groups: ad libitum (AL), intermittent feeding (IF) (food given every other day), and AL and IF control groups. After five weeks, AL and IF groups were given a single oral dose of 20 or 60mg/kg MDMA. Behavior was assessed with the elevated plus-maze and the open field tests. Each of the treatment groups were then divided in to two groups: AL-AL (AL diet throughout), AL-IF (IF after MDMA administration), IF-IF (IF diet throughout), IF-AL (AL after MDMA administration). The second behavioral assessment was performed on ninth and 12th day after MDMA administration. The brains were then prepared with cresyl fast violet stain for stereology of the CA1 area of hippocampus. Results: The AL groups showed enhanced locomotion and anxiety compared to the IF (p<0.001); however, IF groups showed significantly (p<0.05) more locomotor activity and less anxiety recovery at ninth and 12th days compared to the AL animals. The neuronal numerical density was significantly (p<0.05) higher in the hippocampus in the AL-IF groups compared to the AL-AL. Conclusion: IF regimen can significantly modify various behavioral characteristics induced by MDMA and promotes faster recovery from MDMA's anxiogenic effects. Additionally, IF regimen had neuroprotective effects on the neurons of the CA1 area of the hippocampus after a single oral dose of MDMA. We believe the results of our study support the need for further research examining the behavior modifying and neuroprotective potential of the IF regminen for the treatment of drug addiction in humans.

Adolescent exposure to MDMA induces dopaminergic toxicity in substantia nigra and potentiates the amyloid plaque deposition in the striatum of APPswe/PS1dE9 mice

MDMA is one of the most used drugs by adolescents and its consumption has been associated with many psychobiological problems, among them psychomotor problems. Moreover, some authors described that early exposure to MDMA may render the dopaminergic neurons more vulnerable to the effects of future neurotoxic insults. Alzheimer disease (AD) is the main cause of dementia in the elderly and a percentage of the patients have predisposition to suffer nigrostriatal alterations, developing extrapyramidal signs. Nigrostriatal dysfunction in the brain of aged APPswe/PS1dE9 (APP/PS1), a mouse model of familiar AD (FAD), has also been described. The aim of the present study was to investigate the consequences of adolescent exposure to MDMA in APP/PS1 mice, on nigrostriatal function on early adulthood. We used a MDMA schedule simulating weekend binge abuse of this substance. Our MDMA schedule produced a genotype-independent decrease in dopaminergic neurons in the substantia nigra that remained at least 3months. Shortly after the injury, wild-type animals showed a decrease in the locomotor activity and apparent DA depletion in striatum, however in the APP/PS1 mice neither the locomotor activity nor the DA levels were modified, but a reduction in dopamine transporter (DAT) expression and a higher levels of oxidative stress were observed. We found that these disturbances are age-related characteristics that this APP/PS1 mice develops spontaneously much later. Therefore, MDMA administration seems to anticipate the striatal dopaminergic dysfunction in this FAD model. The most important outcome lies in a potentiation, by MDMA, of the amyloid beta deposition in the striatum.

Effect of Some Psychoactive Drugs Used as 'Legal Highs' on Brain Neurotransmitters

New psychoactive "designer drugs" are synthetic compounds developed to provide similar effects to illicit drugs of abuse, but not subjected to legal control. The rapidly changing legal status of novel psychoactive drugs triggers the development of new compounds, analogs of well-known amphetamine or mescaline. New designer drugs used as substitutes in ecstasy pills are the least investigated and can cause life-threatening effects on users. The aim of our research was to examine the effects of acute administration of 4-methoxyamphetamine (PMA, 5 and 10 mg/kg), 4-methoxy-N-methylamphetamine (PMMA, 5 and 10 mg/kg), and mephedrone (MEPH, 5, 10 and 20 mg/kg) on extracellular and tissue level of dopamine (DA), 5-hydroxytryptamine (5-HT) and their metabolites in rat brain, by microdialysis method in freely moving animals and HPLC. Similarly to 3,4-methylenedioxymethamphetamine (MDMA, 5 and 10 mg/kg) PMA, PMMA and MEPH enhanced the release of DA and 5-HT in rat striatum, nucleus accumbens, and frontal cortex. DA tissue content was increased by MEPH and PMMA in striatum, by MEPH, PMA, and PMMA in nucleus accumbens, and by PMA in frontal cortex. Instead, cortical DA level was decreased by MEPH and PMMA. MEPH did not influence 5-HT tissue level in striatum and nucleus accumbens, but decreased its level in frontal cortex. PMMA increased 5-HT content in striatum, while PMA enhanced it in nucleus accumbens and frontal cortex. Observed changes in brain monoamines and their metabolites by new psychoactive drugs suggest that these drugs may be capable of development of dependence. Further experiments are needed to fully investigate the neurotoxic and abuse potential of those drugs.

Amphetamine-related drugs neurotoxicity in humans and in experimental animals: Main mechanisms

Amphetamine-related drugs, such as 3,4-methylenedioxymethamphetamine (MDMA) and methamphetamine (METH), are popular recreational psychostimulants. Several preclinical studies have demonstrated that, besides having the potential for abuse, amphetamine-related drugs may also elicit neurotoxic and neuroinflammatory effects. The neurotoxic potentials of MDMA and METH to dopaminergic and serotonergic neurons have been clearly demonstrated in both rodents and non-human primates. This review summarizes the species-specific cellular and molecular mechanisms involved in MDMA and METH-mediated neurotoxic and neuroinflammatory effects, along with the most important behavioral changes elicited by these substances in experimental animals and humans. Emphasis is placed on the neuropsychological and neurological consequences associated with the neuronal damage. Moreover, we point out the gap in our knowledge and the need for developing appropriate therapeutic strategies to manage the neurological problems associated with amphetamine-related drug abuse.

Ecstasy (MDMA) Alters Cardiac Gene Expression and DNA Methylation: Implications for Circadian Rhythm Dysfunction in the Heart

MDMA (ecstasy) is an illicit drug that stimulates monoamine neurotransmitter release and inhibits reuptake. MDMA's acute cardiotoxicity includes tachycardia and arrhythmia which are associated with cardiomyopathy. MDMA acute cardiotoxicity has been explored, but neither long-term MDMA cardiac pathological changes nor epigenetic changes have been evaluated. Microarray analyses were employed to identify cardiac gene expression changes and epigenetic DNA methylation changes. To identify permanent MDMA-induced pathogenetic changes, mice received daily 10- or 35-day MDMA, or daily 10-day MDMA followed by 25-day saline washout (10 + 25 days). MDMA treatment caused differential gene expression (p < .05, fold change >1.5) in 752 genes following 10 days, 558 genes following 35 days, and 113 genes following 10-day MDMA + 25-day saline washout. Changes in MAPK and circadian rhythm gene expression were identified as early as 10 days. After 35 days, circadian rhythm genes (Per3, CLOCK, ARNTL, and NPAS2) persisted to be differentially expressed. MDMA caused DNA hypermethylation and hypomethylation that was independent of gene expression; hypermethylation of genes was found to be 71% at 10 days, 68% at 35 days, and 91% at 10 + 25 days washout. Differential gene expression paralleled DNA methylation in 22% of genes at 10-day treatment, 17% at 35 days, and 48% at 10 + 25 days washout. We show here that MDMA induced cardiac epigenetic changes in DNA methylation where hypermethylation predominated. Moreover, MDMA induced gene expression of key elements of circadian rhythm regulatory genes. This suggests a fundamental organism-level event to explain some of the etiologies of MDMA dysfunction in the heart.

The novelty-seeking phenotype modulates the long-lasting effects of adolescent MDMA exposure

Exposure to drugs such as ethanol or cocaine during adolescence induces alterations in the central nervous system that are modulated by the novelty-seeking trait. Our aim was to evaluate the influence of this trait on the long-term effects of MDMA administration during adolescence on spontaneous behavior and conditioned rewarding effects in adulthood. Adolescent mice were classified as high or low novelty seekers (HNS or LNS) according to the hole-board test and received either MDMA (0, 10 or 20mg/kg PND 33-42) or saline. Three weeks later, having entered adulthood (PND>68), one set of mice performed the elevated plus maze and social interaction tests, while another set performed the conditioning place preference (CPP) test induced by cocaine-(1mg/kg) or MDMA-(1mg/kg). Only HNS mice treated with MDMA during adolescence acquired CPP in adulthood with a non-effective dose of cocaine or MDMA. Although it did not produce changes in motor activity, exposure to MDMA during adolescence was associated with more aggressive behaviors (threat and attack) and increased social contacts in HNS mice, while an anxiolytic effect was noted in LNS mice pre-treated with the highest dose of MDMA (20mg/kg). Administration of MDMA (10 or 20mg/kg) induced a decrease in DA levels in the striatum in LNS mice only and lower striatal serotonin levels in mice treated with the highest MDMA dose. Our findings show that adolescent MDMA exposure results in higher sensitivity to the conditioned reinforcing properties of MDMA and cocaine in adult HNS mice, which suggests that the relationship between exposure to MDMA in adolescence and a higher probability of substance is a feature of high novelty seekers only.

The role of adenosine A1 and A2A receptors in the caffeine effect on MDMA-induced DA and 5-HT release in the mouse striatum

3,4-Methylenedioxymethamphetamine (MDMA, “ecstasy”) popular as a designer drug is often used with caffeine to gain a stronger stimulant effect. MDMA induces 5-HT and DA release by interaction with monoamine transporters. Co-administration of caffeine and MDMA may aggravate MDMA-induced toxic effects on DA and 5-HT terminals. In the present study, we determined whether caffeine influences DA and 5-HT release induced by MDMA. We also tried to find out if adenosine A1 and A2A receptors play a role in the effect of caffeine by investigating the effect of the selective adenosine A1 and A2A receptor antagonists, DPCPX and KW 6002 on DA and 5-HT release induced by MDMA. Mice were treated with caffeine (10 mg/kg) and MDMA (20 or 40 mg/kg) alone or in combination. DA and 5-HT release in the mouse striatum was measured using in vivo microdialysis. Caffeine exacerbated the effect of MDMA on DA and 5-HT release. DPCPX or KW 6002 co-administered with MDMA had similar influence as caffeine, but KW 6002 was more potent than caffeine or DPCPX. To exclude the contribution of MAO inhibition by caffeine in the caffeine effect on MDMA-induced increase in DA and 5-HT, we also tested the effect of the nonxanthine adenosine receptor antagonist CGS 15943A lacking properties of MAO activity modification. Our findings indicate that adenosine A1 and A2A receptor blockade may account for the caffeine-induced exacerbation of the MDMA effect on DA and 5-HT release and may aggravate MDMA toxicity.

3,4-Methylenedioxymethamphetamine enhances kainic acid convulsive susceptibility

Kainic acid (KA) causes seizures and neuronal loss in the hippocampus. The present study investigated whether a recreational schedule of 3,4-methylenedioxymethamphetamine (MDMA) favours the development of a seizure state in a model of KA-induced epilepsy and potentiates the toxicity profile of KA (20 or 30mg/kg). Adolescent male C57BL/6 mice received saline or MDMA t.i.d. (s.c. every 3h), on 1day a week, for 4 consecutive weeks. Twenty-four hours after the last MDMA exposure, the animals were injected with saline or KA (20 or 30mg/kg). After this injection, we evaluated seizures, hippocampal neuronal cell death, microgliosis, astrogliosis, and calcium binding proteins. MDMA pretreatment, by itself, did not induce neuronal damage but increased seizure susceptibility in all KA treatments and potentiated the presence of Fluoro-Jade-positive cells in CA1. Furthermore, MDMA, like KA, significantly decreased parvalbumin levels in CA1 and dentate gyrus, where it potentiated the effects of KA. The amphetamine derivative also promoted a transient decrease in calbindin and calretinin levels, indicative of an abnormal neuronal discharge. In addition, treatment of cortical neurons with MDMA (10-50μM) for 6 or 48h significantly increased basal Ca(2+), reduced basal Na(+) levels and potentiated kainate response. These results indicate that MDMA potentiates KA-induced neurodegeneration and also increases KA seizure susceptibility. The mechanism proposed includes changes in Calcium Binding Proteins expression, probably due to the disruption of intracellular ionic homeostasis, or/and an indirect effect through glutamate release.

Administration of S-methyl-L-thiocitrulline protects against brain injuries after intracerebral hemorrhage

Although intracerebral hemorrhage (ICH) increases the level of glutamate in the perihematomal area and cerebral spinal fluid (CSF) in the ICH acute phase, it is unclear whether elevated glutamate activates neuronal nitric oxide synthase (nNOS) in the ICH brain and whether nNOS is an important target for ICH treatment. Here, we assessed the role of the nNOS inhibitor S-methyl-l-thiocitrulline (SMTC) in the activity of NADPH-d and ICH-induced brain injuries. An autologous blood intracerebral infusion model in male rats was used. All of the rats were sacrificed 24h after ICH. ICH increased NADPH-d activity in the striatum. Administering SMTC 3h after ICH decreased the activity of NADH-d (p<0.05 vs. the ICH group). The activation of gelatinolytic enzymes in the perihematomal region of the striatum was reduced by SMTC treatment (p<0.01, vs. the ICH group). The loss of laminin- and occludin-stained vessels was significant in perihematomal regions after 24h of ICH and was significantly attenuated by the administration of SMTC (p<0.01 for laminin, p<0.05 for occluding, compared with the ICH group). Neuronal death and neurological deficits after ICH were also decreased in SMTC treatment rats (p<0.01, vs. the ICH group). The results suggest that the administration of the nNOS inhibitor SMTC after ICH protects against ICH-induced brain injuries and improves neurological function.

Cocaine potentiates MDMA-induced oxidative stress but not dopaminergic neurotoxicity in mice: implications for the pathogenesis of free radical-induced neurodegenerative disorders

RATIONALE

The drugs of abuse 3,4-methylenedioxymethamphetamine (MDMA; "ecstasy") and cocaine both increase the generation of free radicals, and in the case of MDMA, this increase in oxidative stress is involved in the dopaminergic neurotoxicity produced by the drug in mice. Oxidative stress processes are also involved in the pathogenesis of several neurodegenerative diseases.

OBJECTIVES

We aimed to determine the consequences of the combined administration of MDMA and cocaine on oxidative stress and dopaminergic neurotoxicity.

METHODS

Mice received MDMA (20 mg/kg, i.p.; two doses separated by 3 h) followed by cocaine 1, 3, 6, or 24 h after the second MDMA dose. Mice were killed between 1 h and 7 days after cocaine injection.

RESULTS

MDMA decreased dopamine transporter density and dopamine concentration 7 days later. Cocaine did not alter this neurotoxicity. MDMA produced an increase in the concentration of 2,3-dihydroxybenzoic acid in striatal microdialysis samples and an increase in lipid peroxidation in the striatum which were potentiated by cocaine. MDMA and cocaine given together also increased nitrate and 3-nitrotyrosine levels compared with either drug given alone. On the other hand, MDMA increased superoxide dismutase activity and decreased catalase activity, changes which were prevented by cocaine administration. In addition, cocaine administration produced an increase in glutathione peroxidase (GPx) activity in both saline-treated and MDMA-treated mice.

CONCLUSIONS

Cocaine potentiates MDMA-induced oxidative stress but does not produce an increase in the neurotoxicity produced by MDMA, and this lack of potentiation may involve an increase in GPx activity.

Memantine attenuates 3,4-methylenedioxymethamphetamine-induced hyperthermia in rats

3,4-Methylenedioxymethamphetamine (MDMA) is an illegal drug that can induce life-threatening hyperthermia. No effective pharmacological treatment for MDMA-induced hyperthermia has yet been established. We investigated the effects of memantine, a non-competitive N-methyl-D-aspartate (NMDA)-type glutamate receptor antagonist and an α-7 nicotinic acetylcholine receptor (nAChR) antagonist, on MDMA-induced hyperthermia in rats. Treatment of animals with memantine (10 or 20 mg/kg) either before or after MDMA (10 mg/kg) administration significantly decreased the peak body temperature. Results from our microdialysis study indicated that pretreatment with memantine (20 mg/kg) before MDMA administration had no effect on the MDMA-induced increase in serotonin (5-HT) and dopamine (DA) levels in the anterior hypothalamus. MDMA-induced hyperthermia was significantly suppressed by pretreatment with the non-competitive NMDA receptor antagonist MK-801 (0.5 mg/kg) and the competitive NMDA antagonist CGS 19755 (5 mg/kg), but not by the selective α-7 nAChR antagonist methyllycaconitine (6 or 10 mg/kg). These results indicate that the inhibitory effect of memantine on MDMA-induced hyperthermia may be due to its activity as an NMDA receptor antagonist and not as a result of a direct effect on the 5-HT or DA systems. The present study suggests that moderate doses of memantine may be useful for the treatment of MDMA-induced hyperthermia in humans.

Lost in translation: preclinical studies on 3,4-methylenedioxymethamphetamine provide information on mechanisms of action, but do not allow accurate prediction of adverse events in humans

3,4-Methylenedioxymethamphetamine (MDMA) induces both acute adverse effects and long-term neurotoxic loss of brain 5-HT neurones in laboratory animals. However, when choosing doses, most preclinical studies have paid little attention to the pharmacokinetics of the drug in humans or animals. The recreational use of MDMA and current clinical investigations of the drug for therapeutic purposes demand better translational pharmacology to allow accurate risk assessment of its ability to induce adverse events. Recent pharmacokinetic studies on MDMA in animals and humans are reviewed and indicate that the risks following MDMA ingestion should be re-evaluated. Acute behavioural and body temperature changes result from rapid MDMA-induced monoamine release, whereas long-term neurotoxicity is primarily caused by metabolites of the drug. Therefore acute physiological changes in humans are fairly accurately mimicked in animals by appropriate dosing, although allometric dosing calculations have little value. Long-term changes require MDMA to be metabolized in a similar manner in experimental animals and humans. However, the rate of metabolism of MDMA and its major metabolites is slower in humans than rats or monkeys, potentially allowing endogenous neuroprotective mechanisms to function in a species specific manner. Furthermore acute hyperthermia in humans probably limits the chance of recreational users ingesting sufficient MDMA to produce neurotoxicity, unlike in the rat. MDMA also inhibits the major enzyme responsible for its metabolism in humans thereby also assisting in preventing neurotoxicity. These observations question whether MDMA alone produces long-term 5-HT neurotoxicity in human brain, although when taken in combination with other recreational drugs it may induce neurotoxicity.

Behavioural and neuroinflammatory effects of the combination of binge ethanol and MDMA in mice

RATIONALE

Binge drinking is a common pattern of alcohol consumption among young people. Binge drinkers are especially susceptible to brain damage when other substances are co-administered, in particular, 3,4-methylendioxymethamphetamine (MDMA).

OBJECTIVE

To evaluate the behavioural consequences of voluntary binge ethanol consumption, alone and in combination to MDMA. Also, to elucidate the effects of the combined consumption of these two drugs on neuroinflammation.

MATERIALS AND METHODS

Adolescent mice received MDMA (MDMA-treated mice), ethanol (ethanol-treated mice group) or both (ethanol plus MDMA-treated mice). Drinking in the dark (DID) procedure was used as a model of binge. Body temperature, locomotor activity, motor coordination, anxiety-like and despair behaviour in adolescent mice were evaluated 48 h, 72 h, and 7 days after the treatments. Also, neuroinflammatory response to these treatments was measured in the striatum.

RESULTS

The hyperthermia observed in MDMA-treated mice was abolished by pre-exposition to ethanol. Ethanol plus MDMA-treated mice showed lower locomotor activity. Ethanol-treated mice showed motor coordination impairment and increased despair behaviour. Anxiety-like behaviour was only seen in animals that were treated with both drugs. Contrarily, neuroinflammation was mostly seen in animals treated only with MDMA.

CONCLUSIONS

Ethanol and MDMA co-administration increases the neurobehavioural changes induced by the consumption of each one of these drugs. However, as ethanol consumption did not increase neuroinflammatory responses induced by MDMA, other mechanisms, mediated by ethanol, are likely to account for this effect and need to be evaluated.

Enhanced Hyperthermia Induced by MDMA in Parkin Knockout Mice

MDMA (3,4-methylenedioxymethamphetamine) is reportedly severely toxic to both dopamine (DA) and serotonin neurons. MDMA significantly reduces the number of DA neurons in the substantia nigra, but not in the nucleus accumbens, indicating that MDMA causes selective destruction of DA neurons in the nigrostriatal pathway, sparing the mesolimbic pathway. Parkinson’s disease (PD) is a neurodegenerative disorder of multifactorial origin. The pathological hallmark of PD is the degeneration of DA neurons in the nigrostriatal pathway. Mutations in the parkin gene are frequently observed in autosomal recessive parkinsonism in humans. Parkin is hypothesized to protect against neurotoxic insult, and we attempted to clarify the role of parkin in MDMA-induced hyperthermia, one of the causal factors of neuronal damage, using parkin knockout mice. Body temperature was measured rectally before and 15, 30, 45, and 60 min after intraperitoneal injection of MDMA (30 mg/kg) at an ambient temperature of 22 ± 2°C. Significantly enhanced hyper-thermia after MDMA injection was observed in heterozygous and homozygous parkin knockout mice compared with wildtype mice, suggesting that parkin plays a protective role in MDMA neurotoxicity.

Intermittent ethanol exposure increases long-lasting behavioral and neurochemical effects of MDMA in adolescent mice

RATIONALE

Heavy binge drinking is increasingly frequent among adolescents, while ethanol (EtOH) is often used in combination with 3,4-methylenedioxymethamphetamine (MDMA).

OBJECTIVES

The long-lasting effects of intermittent exposure to EtOH and MDMA during adolescence on motor activity, anxiety, and social behavior were evaluated in adult mice. The concentration of brain monoamines in the striatum, cortex, and hippocampus was measured following the behavioral test.

METHODS

Adolescent OF1 mice were exposed to ethanol (1.25 g/kg) on two consecutive days at 48-h intervals over a 14-day period (from PND 29 to 42). A total of eight injections of MDMA (10 or 20 mg/kg) were administered twice daily at 4-h intervals over two consecutive days, and this schedule was repeated 6 days later (PND 33, 34, 41, and 42). Behavioral tests and analysis of brain monoamines took place on PND 64 to 67.

RESULTS

Exposure to MDMA during adolescence increased the anxiogenic response in the elevated plus maze, with adult mice spending less time in the open arms of the maze and exhibiting lower concentrations of DA in the striatum. A pattern of ethanol administration modeling binge drinking during adolescence enhanced these effects and undermined the hyperthermic response induced by MDMA. Passive avoidance was affected only when EtOH was administered alone.

CONCLUSIONS

Juvenile administration of MDMA and alcohol was found to cause a decrease in monoamine levels in adulthood, as well as changes in social interaction behaviors, locomotor activity, increase measures of anxiety in the elevated plus maze (EPM), and decrease step-through latencies in passive avoidance test.

MDMA (ecstasy) enhances loud noise-induced morphofunctional alterations in heart and adrenal gland

Noise is an environmental stressor increasingly more present in modern life and, in particular, in a variety of recreational contexts. The aim of this work is to show the effects of noise on the myocardium and adrenal gland, through a careful review of the literature dealing with the peripheral effects of noise exposure in experimental and clinical studies. Noise induces adverse effects in human health, principally involving the cardiovascular and autonomic nervous systems, and the endocrine apparatus. Several factors in recreational environments potentially worsen the effects induced by loud noise. Among these, the intake of 3,4-methylenedioxymethamphetamine (MDMA) is frequently associated with noise exposure in recreational situations, because of its high compliance within social and relaxation settings. For this reason, MDMA is defined as a club drug--as its intake by young people often occurs in association with other factors, such as aggregation, high temperatures, and noise. It is known that self-administration of MDMA by humans causes severe toxicity. In particular, the myocardium is affected early after MDMA intake--resulting in tachycardia, hypertension, and arrhythmia. Furthermore, MDMA alters the activity of the adrenal glands by elevating catecholamines and corticosterone levels. This review shows that combining MDMA and loud noise exposure potentiates the effects that are produced by each single stimulant alone as seen in experimental animal models. The convergence of the effects of prolonged loud noise exposure and the consumption of MDMA on the same system might explain the sudden fatal events that happen in recreational situations.

Neuronal Nicotinic Receptors as New Targets for Amphetamine-Induced Oxidative Damage and Neurotoxicity

Amphetamine derivatives such as methamphetamine (METH) and 3,4-methylenedioxymethamphetamine (MDMA, “ecstasy”) are widely abused drugs in a recreational context. This has led to concern because of the evidence that they are neurotoxic in animal models and cognitive impairments have been described in heavy abusers. The main targets of these drugs are plasmalemmal and vesicular monoamine transporters, leading to reverse transport and increased monoamine efflux to the synapse. As far as neurotoxicity is concerned, increased reactive oxygen species (ROS) production seems to be one of the main causes. Recent research has demonstrated that blockade of α7 nicotinic acetylcholine receptors (nAChR) inhibits METH- and MDMA-induced ROS production in striatal synaptosomes which is dependent on calcium and on NO-synthase activation. Moreover, α7 nAChR antagonists (methyllycaconitine and memantine) attenuated in vivo the neurotoxicity induced by METH and MDMA, and memantine prevented the cognitive impairment induced by these drugs. Radioligand binding experiments demonstrated that both drugs have affinity to α7 and heteromeric nAChR, with MDMA showing lower K_i values, while fluorescence calcium experiments indicated that MDMA behaves as a partial agonist on α7 and as an antagonist on heteromeric nAChR. Sustained Ca increase led to calpain and caspase-3 activation. In addition, modulatory effects of MDMA on α7 and heteromeric nAChR populations have been found.

The intriguing effects of ecstasy (MDMA) on cognitive function in mice subjected to a minimal traumatic brain injury (mTBI)

RATIONALE

The use of ecstasy (MDMA) among young adults has dramatically increased over the years. Since MDMA may impair the users' driving ability, the risk of being involved in a motor vehicle accident (MVA) is notably increased. Minimal traumatic brain injury (mTBI) a common consequence of MVAs-produces short- and long-term physical, cognitive, and emotional impairments.

OBJECTIVES

To investigate the effects of an acute dose of MDMA in mice subjected to closed head mTBI.

METHODS

Mice received 10 mg/kg MDMA 1 h prior to the induction of mTBI. Behavioral tests were conducted 7 and 30 days post-injury. In addition to the behavioral tests, phosphorylation of IGF-1R, ERK, and levels of tyrosine hydroxylase (TH) were measured.

RESULTS

mTBI mice showed major cognitive impairments in all cognitive tests conducted. No additional impairments were seen if mTBI was preceded by one dose of MDMA. On the contrary, a beneficial effect was seen in these mice. The western blot analysis of TH revealed a significant decrease in the mTBI mice. These decreases were reversed in mice that were subjected to MDMA prior to the trauma.

CONCLUSIONS

The presence of MDMA at the time of mTBI minimizes the alteration of visual and spatial memory of the injured mice. The IGF-1R pathway was activated due to mTBI and MDMA but was not the main contributor to the cognitive improvements. MDMA administration inverted the TH decreases seen after injury. We believe this may be the major cause of the cognitive improvements seen in these mice.

The role of monoamines in the changes in body temperature induced by 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) and its derivatives

Hyperthermia is probably the most widely known acute adverse event that can follow ingestion of 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) by recreational users. The effect of MDMA on body temperature is complex because the drug has actions on all three major monoamine neurotransmitters [5-hydroxytryptamine (5-HT), dopamine and noradrenaline], both by amine release and by direct receptor activation. Hyperthermia and hypothermia can be induced in laboratory animals by MDMA, depending on the ambient temperature, and involve both central thermoregulation and peripheral changes in blood flow and thermogenesis. Acute 5-HT release is not directly responsible for hyperthermia, but 5-HT receptors are involved in modulating the hyperthermic response. Impairing 5-HT function with a neurotoxic dose of MDMA or p-chlorophenylalanine alters the subsequent MDMA-induced hyperthermic response. MDMA also releases dopamine, and evidence suggests that this transmitter is involved in both the hyperthermic and hypothermic effects of MDMA in rats. The noradrenergic system is also involved in the hyperthermic response to MDMA. MDMA activates central alpha(2A)-adrenoceptors and peripheral alpha(1)-adrenoceptors to produce cutaneous vasoconstriction to restrict heat loss, and beta(3)-adrenoceptors in brown adipose tissue to increase heat generation. The hyperthermia occurring in recreational users of MDMA can be fatal, but data reviewed here indicate that it is unlikely that any single pharmaceutical agent will be effective in reversing the hyperthermia, so careful body cooling remains the principal clinical approach. Crucially, educating recreational users about the potential dangers of hyperthermia and the control of ambient temperature should remain key approaches to prevent this potentially fatal problem.

Methylenedioxymethamphetamine inhibits mitochondrial complex I activity in mice: a possible mechanism underlying neurotoxicity

BACKGROUND AND PURPOSE

3,4-methylenedioxymethamphetamine (MDMA) causes a persistent loss of dopaminergic cell bodies in the substantia nigra of mice. Current evidence indicates that such neurotoxicity is due to oxidative stress but the source of free radicals remains unknown. Inhibition of mitochondrial electron transport chain complexes by MDMA was assessed as a possible source.

EXPERIMENTAL APPROACH

Activities of mitochondrial complexes after MDMA were evaluated spectrophotometrically. In situ visualization of superoxide production in the striatum was assessed by ethidium fluorescence and striatal dopamine levels were determined by HPLC as an index of dopaminergic toxicity.

KEY RESULTS

3,4-methylenedioxymethamphetamine decreased mitochondrial complex I activity in the striatum of mice, an effect accompanied by an increased production of superoxide radicals and the inhibition of endogenous aconitase. alpha-Lipoic acid prevented superoxide generation and long-term toxicity independent of any effect on complex I inhibition. These effects of alpha-lipoic acid were also associated with a significant increase of striatal glutathione levels. The relevance of glutathione was supported by reducing striatal glutathione content with L-buthionine-(S,R)-sulfoximine, which exacerbated MDMA-induced dopamine deficits, effects suppressed by alpha-lipoic acid. The nitric oxide synthase inhibitor, N(G)-nitro-L-arginine, partially prevented MDMA-induced dopamine depletions, an effect reversed by L-arginine but not D-arginine. Finally, a direct relationship between mitochondrial complex I inhibition and long-term dopamine depletions was found in animals treated with MDMA in combination with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine.

CONCLUSIONS AND IMPLICATIONS

Inhibition of mitochondrial complex I following MDMA could be the source of free radicals responsible for oxidative stress and the consequent neurotoxicity of this drug in mice.

Reduced 3,4-methylenedioxymethamphetamine (MDMA, Ecstasy)-initiated oxidative DNA damage and neurodegeneration in prostaglandin H synthase-1 knockout mice

The neurodegenerative potential of 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) and underlying mechanisms are under debate. Here, we show that MDMA is a substrate for CNS prostaglandin H synthase (PHS)-catalyzed bioactivation to a free radical intermediate that causes reactive oxygen species (ROS) formation and neurodegenerative oxidative DNA damage. In vitro PHS-1-catalyzed bioactivation of MDMA stereoselectively produced free radical intermediate formation and oxidative DNA damage that was blocked by the PHS inhibitor eicosatetraynoic acid. In vivo, MDMA stereoselectively caused gender-independent DNA oxidation and dopaminergic nerve terminal degeneration in several brain regions, dependent on regional PHS-1 levels. Conversely, MDMA-initiated striatal DNA oxidation, nerve terminal degeneration, and motor coordination deficits were reduced in PHS-1 +/- and -/- knockout mice in a gene dose-dependent fashion. These results confirm the neurodegenerative potential of MDMA and provide the first direct evidence for a novel molecular mechanism involving PHS-catalyzed formation of a neurotoxic MDMA free radical intermediate.

Administration of neurotoxic doses of MDMA reduces sensitivity to ethanol and increases GAT-1 immunoreactivity in mice striatum

RATIONALE

Mice with reduced dopamine activity following neurotoxic doses of 3,4-methylenedioxymethamphetamine (MDMA, 'ecstasy') consume more ethanol (EtOH) and show greater preference for EtOH. In keeping with human studies and other animal models where alcohol consumption and preference are also high, MDMA treatment will reduce sensitivity to certain physiological effects of EtOH.

OBJECTIVE

We have examined the sensitivity to the acute effects of EtOH in MDMA-lesioned mice and the effects of EtOH on striatal gamma-aminobutyric acid (GABA) accumulation and expression of GABA subtype-1 transporter (GAT-1).

METHODS

C57BL/6J mice were injected with neurotoxic MDMA (30 mg/kg, three times, every 3 h, i.p.). Seven days later, mice were given EtOH (3 g/kg, i.p.) to determine the loss of righting response and the development of rapid tolerance to the hypothermic effect of EtOH. The effect of EtOH on the striatal accumulation of GABA after inhibiting GABA transaminase and on GAT-1 immunoreactivity was also determined.

RESULTS

Mice pre-treated with a neurotoxic dose of MDMA were less sensitive to the sedative-hypnotic effect of acute EtOH and exhibited alterations in the development of rapid tolerance to the hypothermic effect of EtOH. These animals showed an increase in striatal GAT-1 immunoreactivity. EtOH reduced GABA concentration in the striatum of non-lesioned mice, an effect not observed in MDMA-lesioned mice.

CONCLUSION

These findings indicate that mice with a MDMA-induced dopaminergic lesion show increased expression of striatal GAT-1 that may contribute to the lower sensitivity to EtOH-induced sedative effects and the resistance to the development of rapid tolerance to hypothermia produced by EtOH.

Dopamine transporter down-regulation following repeated cocaine: implications for 3,4-methylenedioxymethamphetamine-induced acute effects and long-term neurotoxicity in mice

BACKGROUND AND PURPOSE

3,4-Methylenedioxymethamphetamine (MDMA) and cocaine are two widely abused psychostimulant drugs targeting the dopamine transporter (DAT). DAT availability regulates dopamine neurotransmission and uptake of MDMA-derived neurotoxic metabolites. We aimed to determine the effect of cocaine pre-exposure on the acute and long-term effects of MDMA in mice.

EXPERIMENTAL APPROACH

Mice received a course of cocaine (20 mg*kg(-1), x2 for 3 days) followed by MDMA (20 mg*kg(-1), x2, 3 h apart). Locomotor activity, extracellular dopamine levels and dopaminergic neurotoxicity were determined. Furthermore, following the course of cocaine, DAT density in striatal plasma membrane and endosome fractions was measured.

KEY RESULTS

Four days after the course of cocaine, challenge with MDMA attenuated the MDMA-induced striatal dopaminergic neurotoxicity. Co-administration of the protein kinase C (PKC) inhibitor NPC 15437 prevented cocaine protection. At the same time, after the course of cocaine, DAT density was reduced in the plasma membrane and increased in the endosome fraction, and this effect was prevented by NPC 15437. The course of cocaine potentiated the MDMA-induced increase in extracellular dopamine and locomotor activity, following challenge 4 days later, compared with those pretreated with saline.

CONCLUSIONS AND IMPLICATIONS

Repeated cocaine treatment followed by withdrawal protected against MDMA-induced dopaminergic neurotoxicity by internalizing DAT via a mechanism which may involve PKC. Furthermore, repeated cocaine followed by withdrawal induced behavioural and neurochemical sensitization to MDMA, measures which could be indicative of increased rewarding effects of MDMA.

Methamphetamine self-administration and the effect of contingency on monoamine and metabolite tissue levels in the rat

A number of studies have shown that exposure to high doses of methamphetamine (MA) is toxic to central dopamine (DA) and serotonin (5-HT) neurons. In most of those studies, however, high doses of MA were experimenter-administered during a short exposure time. Because contingency is a determinant for many effects of drug exposure, the present objective was to investigate the effects of self-administered MA on tissue monoamine levels following a short (24 hours) or longer (7 days) withdrawal period. As previously reported, a noncontingent "binge" high-dose treatment regimen (4 injections of 10 mg/kg MA administered every 2 hours) produced persistent depletion of cortical 5-HT and striatal DA. Effects of self-administered MA (0.1 mg/kg/infusion) were then determined following a 20-day duration where a yoked design was employed such that some rats received MA contingent on an operant lever press and others received either MA or saline dependent on the responses of the contingent rat. Self-administered MA produced a transient striatal DA depletion with a more persistent increase in DA turnover, indicating the presence of some lasting adaptations. Furthermore, the yoked design revealed that there was no effect of contingency on these parameters.

S100B overexpressing mutant mice exhibit prolonged behavioural and biochemical responses towards repeated intermittent binge treatments with MDMA

The recreational drug 3,4-methylenedioxy-metamphetamine (MDMA; 'ecstasy') enhances serotonin and dopamine transmission. Repeated binge treatment with MDMA (5 mg/kg, 3 times daily, 3 h apart, once per week for 4 wk) was found to increase gene expression of S100B, a neurotrophic factor that modulates neuronal plasticity. Mutant mice overexpressing S100B were investigated to better understand how increased S100B expression may influence MDMA-induced biochemical and behavioural responses. In open-field behaviour, the later MDMA binges decreased rearing and thigmotaxis in S100B mutant mice compared to wild-type mice. In the elevated plus-maze, MDMA increased open-arm entries in both genotypes, but less tolerance to this effect was found in S100B mutant mice. Serotonin transporter (SERT) density was up-regulated in the substantia nigra in S100B mutant mice under baseline conditions. MDMA treatment increased SERT in wild-type mice, but did not further increase it in S100B mutant mice. Dopamine transporter density was down-regulated by MDMA in both genotypes in the striatum. 5-HT1B receptor density and G-protein coupling were higher in MDMA-treated S100B mutant mice than in saline-treated mutant mice and MDMA-treated wild-type mice in the medial globus pallidus. In conclusion, repeated MDMA treatment increases S100B mRNA. Certain explorative and anxiolytic-like behaviours in response to MDMA are potentiated and exhibit less tolerance in mice overexpressing S100B. The genotype-dependent behavioural responses are paralleled by adaptations in the serotonin system. Our data indicate that genetic differences in S100B gene expression may predispose individual differences in the responsivity to repeated intake of MDMA.

Involvement of nicotinic receptors in methamphetamine- and MDMA-induced neurotoxicity: pharmacological implications

During the last years, we have focused on the study of the neurotoxic effects of 3,4-methylenedioxymethamphetamine (MDMA) and methamphetamine (METH) on the central nervous system (CNS) and their pharmacological prevention methods. In the process of this research, we have used a semipurified synaptosomal preparation from striatum of mice or rats as a reliable in vitro model to study reactive oxygen species (ROS) production by these amphetamine derivatives, which is well-correlated with their dopaminergic injury in in vivo models. Using this preparation, we have demonstrated that blockade of alpha7 nicotinic receptors with methyllycaconitine (MLA) prevents ROS production induced by MDMA and METH. Consequently, in vivo, MLA significantly prevents MDMA- and METH-induced neurotoxicity at dopaminergic level (mouse striatum), without affecting hyperthermia induced by these amphetamines. Additionally, when neuroprotection was assayed with memantine (MEM), a dual antagonist of NMDA and alpha7 receptors, an effective neuroprotection was obtained also ahead of serotonergic injury induced by MDMA in rats. MEM also prevents MDMA effect on serotonin transporter functionality and METH effect on dopamine transporter (DAT), suggesting that behavioral effects of these psychostimulants can also be modulated by MEM. Finally, we have demonstrated that MEM prevents the impaired memory function induced by MDMA, and also, using binding studies with radioligands, we have characterized the interaction of these substances with nicotinic receptors. Studies at molecular level showed that both MDMA and METH displaced competitively the binding of radioligands with homomeric alpha7 and heteromeric nicotinic acetylcholine receptors (nAChRs), indicating that they can directly interact with them. In all the cases, MDMA displayed higher affinity than METH and it was higher for heteromeric than for alpha7 subtype. Pre-incubation of differentiated PC12 cells with MDMA or METH induces nAChR upregulation in a concentration- and time-dependent manner, as many nicotinic ligands do, supporting their functional interaction with nAChRs. Such interaction expands the pharmacological profile of amphetamines and can account for some of their effects.