Acute and long-term effects of MDMA on cerebral dopamine biochemistry and function

MDMA for the Treatment of Negative Symptoms in Schizophrenia

The profound economic burden of schizophrenia is due, in part, to the negative symptoms of the disease, which can severely limit daily functioning. There is much debate in the field regarding their measurement and classification and there are no FDA-approved treatments for negative symptoms despite an abundance of research. 3,4-Methylenedioxy methamphetamine (MDMA) is a schedule I substance that has emerged as a novel therapeutic given its ability to enhance social interactions, generate empathy, and induce a state of metaplasticity in the brain. This review provides a rationale for the use of MDMA in the treatment of negative symptoms by reviewing the literature on negative symptoms, their treatment, MDMA, and MDMA-assisted therapy. It reviews recent evidence that supports the safe and potentially effective use of MDMA to treat negative symptoms and concludes with considerations regarding safety and possible mechanisms of action.

MDMA related neuro-inflammation and adenosine receptors

3,4-methylenedioxymethamphetamine (MDMA) is a world-wide abused psychostimulant, which has the neurotoxic effects on dopaminergic and serotonergic neurons in both rodents and non-human primates. Adenosine acts as a neurotransmitter in the brain through the activation of four specific G-protein-coupled receptors and it acts as a neuromodulator of dopamine neurotransmission. Recent studies suggest that stimulation of adenosine receptors oppose many behavioral effects of methamphetamines. This review summarizes the specific cellular mechanisms involved in MDMA neuroinflammatory effects, along with the protective effects of adenosine receptors.

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.

Ecstasy (3,4-methylenedioxymethamphetamine): Cardiovascular effects and mechanisms

3,4-methylenedioxymethamphetamine or MDMA (known as "ecstasy") is a recreational drug of abuse, popular worldwide for its distinctive psychotropic effects. Currently, the therapeutic potential of MDMA in psychotherapy has attracted a lot of interest from the scientific community, despite the multitude of effects that this drug of abuse elicits on the human body. While neuronal effects have been the most studied, cardiovascular effects have also been described, as increased blood pressure and heart rate are the most recognizable. However, other effects have also been described at the cardiac (impaired cardiac contractile function, arrhythmias, myocardial necrosis and valvular heart disease) and vascular (vasoconstriction, disruption of vascular integrity and altered haemostasis) levels. Several mechanisms have been proposed, from the interaction with monoamine transporters and receptors to the promotion of oxidative stress or the activation of matrix metalloproteinases (MMPs). This review provides an overview of the cardiovascular implications of MDMA intake and underlying mechanisms, relevant when considering its consumption as drug of abuse but also when considering its therapeutic potential in psychiatry. Moreover, the risk/benefit ratio of the therapeutic use of MDMA remains to be fully elucidated from a cardiovascular standpoint, particularly in patients with underlying cardiovascular disease.

Methylenedioxymethamphetamine (MDMA): Serotonergic and dopaminergic mechanisms related to its use and misuse

Methylenedioxymethamphetamine (MDMA) is an amphetamine analogue that preferentially stimulates the release of serotonin (5HT) and results in relatively small increases in synaptic dopamine (DA). The ratio of drug-stimulated increases in synaptic DA, relative to 5HT, predicts the abuse liability; drugs with higher DA:5HT ratios are more likely to be abused. Nonetheless, MDMA is a drug that is misused. Clinical and preclinical studies have suggested that repeated MDMA exposure produces neuroadaptive responses in both 5HT and DA neurotransmission that might explain the development and maintenance of MDMA self-administration in some laboratory animals and the development of a substance use disorder in some humans. In this paper, we describe the research that has demonstrated an inhibitory effect of 5HT on the acquisition of MDMA self-administration and the critical role of DA in the maintenance of MDMA self-administration in laboratory animals. We then describe the circuitry and 5HT receptors that are positioned to modulate DA activity and review the limited research on the effects of MDMA exposure on these receptor mechanisms.

Potential Role of Serum S-100β Protein as a Predictor of Cardiotoxicity and Clinical Poor Outcome in Acute Amphetamine Intoxication

Cardio- and neurotoxicity of amphetamines play an important role in worsening morbidity, making the initial evaluation of the patient's status a potentially lifesaving action. The current study hypothesized that the S-100β serum level could predict the severity of acute amphetamine toxicity and the in-hospital outcome. The current study is a prospective cohort study conducted on 77 patients diagnosed with acute amphetamine exposure and referred to Aseer Poison Control Center, Saudi Arabia. The patients admitted to ICU showed significantly higher serum levels of S-100β in comparison to those not admitted (p < 0.05). Moreover, the S-100β level was significantly elevated among patients with prolonged QTc intervals. Receiver-operating characteristic curve of S-100β serum level as an in-hospital outcome predictor showed that at a cutoff value > 0.430 ug/L, the sensitivity of S-100β serum level as severity predictor was 100%, and the specificity was 74.1%. In conclusion, the current study revealed that the S-100β serum level could be used as an outcome predictor in hospital admission cases due to toxic amphetamine exposure and offers an idea about the cardiac and neuronal involvement. This can help select patients who will benefit most from ICU admission and early management and assess the severity of cases in settings where GC-MS is not available.

Breathing new life into neurotoxic-based monkey models of Parkinson's disease to study the complex biological interplay between serotonin and dopamine

Numerous clinical studies have shown that the serotonergic system also degenerates in patients with Parkinson's disease. The causal role of this impairment in Parkinson's symptomatology and the response to treatment remains to be refined, in particular thanks to approaches allowing the two components DA and 5-HT to be isolated if possible. We have developed a macaque monkey model of Parkinson's disease exhibiting a double lesion (dopaminergic and serotonergic) thanks to the sequential use of MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) and MDMA (3,4-methylenedioxy-N-methamphetamine) (or MDMA prior MPTP). We characterized this monkey model by multimodal imaging (PET, positron emission tomography with several radiotracers; DTI, diffusion tensor imaging), behavioral assessments (parkinsonism, dyskinesia, neuropsychiatric-like behavior) and post-mortem analysis (with DA and 5-HT markers). When administrated after MPTP, MDMA damaged the 5-HT presynaptic system without affecting the remaining DA neurons. The lesion of 5-HT fibers induced by MDMA altered rigidity and prevented dyskinesia and neuropsychiatric-like symptoms induced by levodopa therapy in MPTP-treated animals. Interestingly also, prior MDMA administration aggravates the parkinsonian deficits and associated DA injury. Dystonic postures, action tremor and global spontaneous activities were significantly affected. All together, these data clearly indicate that late or early lesions of the 5-HT system have a differential impact on parkinsonian symptoms in the macaque model of Parkinson's disease. Whether MDMA has an impact on neuropsychiatric-like symptoms such as apathy, anxiety, depression remains to be addressed. Despite its limitations, this toxin-based double-lesioned monkey model takes on its full meaning and provides material for the experimental study of the heterogeneity of patients.

Mephedrone and MDMA: A comparative review

Mephedrone and MDMA are both constituents of party drugs, with mephedrone being relatively new compared to MDMA. This review compares current knowledge regarding the patterns of usage and neuropsychobiological effects of both mephedrone and MDMA. Both drugs share common psychoactive effects, the duration of which is significantly shorter with mephedrone use, attributing towards a pattern of binge use among users. Both drugs have also been associated with adverse health, psychiatric, and neurocognitive problems. Whilst there is extensive research into the psychobiological problems induced by MDMA, the evidence for mephedrone is comparatively limited. The adverse effect profile of mephedrone appears to be less severe than that of MDMA. Users often believe it to be safer, although both drugs have been associated with overdoses. The neurotoxic potential of mephedrone appears to be low, whereas MDMA can cause long-term damage to the serotonergic system, although this needs further investigation. The abuse liability of mephedrone is significantly greater than that of MDMA, raising concerns regarding the impact of lifetime usage on users. Given that mephedrone is relatively new, the effects of long-term exposure are yet to be documented. Future research focused on lifetime users may highlight more severe neuropsychobiological effects from the drug.

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.

The acute toxic and neurotoxic effects of 3,4-methylenedioxymethamphetamine are more pronounced in adolescent than adult mice

3,4-methylenedioxymethamphetamine (MDMA) recently achieved breakthrough status from the Food and Drug Administration (FDA) for post-traumatic stress disorder (PTSD). However, evidence indicates that exposure to toxic doses of MDMA can lead to long-lasting dysregulation of brain monoaminergic neurotransmitters, primarily from studies conducted in young adult rodents. To date, there is a paucity of data on whether toxic doses of MDMA can differentially affect neurotransmitter systems in adolescents and mature adults, which is an important question as adolescents and adults may be differentially vulnerable to MDMA abuse. In the current study, adolescent (6-7 weeks of age) and mature adult (16-18 weeks of age) male, Swiss-Webster mice were exposed to MDMA (20 mg/kg) using a binge-like dosing regimen (4 administrations spaced every 2 h). Acute lethality, acute hyperthermia, and acute decreases in body weight following MDMA administration were more pronounced in adolescent than adult mice. Likewise, acute loss of striatal dopamine neurochemistry was also exacerbated in adolescents, as determined by high-pressure liquid chromatography coupled to electrochemical detection. Exposure to MDMA induced greater turnover of dopamine into its major metabolite dihydroxyphenylacetic acid (DOPAC) in adolescents, but not in adults, suggesting a novel mechanism through which adolescents may show increased vulnerability to the acute toxic and neurotoxic effects of MDMA, or conversely that mature adults show greater protection. These data caution that MDMA exposure in adolescence may be particularly dangerous and that the therapeutic window for MDMA may differ between adolescents and mature adults.

Effects of MDMA on neuroplasticity, amyloid burden and phospho-tau expression in APPswe/PS1dE9 mice

BACKGROUND

3,4-Methylenedioxymethamphetamine (MDMA) is still one of the most consumed drugs by adolescents. Its abuse is related with cognitive impairment, which seems due to maladaptive plasticity and neural stress. In turn, new hypotheses suggest that Alzheimer's disease (AD) may be promoted by neural stressors.

AIMS AND METHODS

To test if there is an increase in vulnerability to AD after chronic MDMA consumption, we investigated the effects of this drug on recognition memory and its neurotoxic and neuroplastic effects in a transgenic mouse model of presymptomatic familiar AD (APP/PS1 dE9, Tg).

RESULTS

MDMA-treated animals showed recognition memory deficits, regardless of genotype, which were accompanied by changes in plasticity markers. Tg mice showed an impaired expression of Arc compared with wild-type animals, but exposure to MDMA induced an increase in the expression of this factor of the same percentage in both genotypes. However, the expression of c-fos, BDNF and p-CREB was not significantly altered by MDMA treatment in Tg mice. Although Tg mice had higher free choline levels than wild-type mice (about 123%), MDMA did not modify these levels in any case, ruling out any specific effect of this drug on the acetylcholine pathway. MDMA treatment significantly increased the presence of cortical amyloid plaques, as well as Aβ40, Aβ42 and secreted APPβ levels in Tg mice. These plaques were accompanied by increased tau phosphorylation (S199), which does not seem to occur via the canonic pathway involving AKT, CDK5 or GSK3β.

CONCLUSIONS

The present results support previous evidences that MDMA can contribute to the amyloid cascade.

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.

Agmatine attenuates methamphetamine-induced passive avoidance learning and memory and CaMKII-α gene expression deteriorations in hippocampus of rat

Methamphetamine (METH) abuse is one the most worldwide problems with wide-ranging effects on the central nervous system (CNS). Chronic METH abuse can associate with cognitive abnormalities and neurodegenerative changes in the brain. Agmatine, a cationic polyamine, has been proposed as a neuromodulator that modulates many effects of abused drugs. The aim of this study was to determine if agmatine can decrease the impairment effect of METH on memory and hippocampal CaMKII-α gene expression, a gene that plays a major role in memory. Male wistar rats (200-220 g) were allocated into 7 groups, including 5 groups of saline, METH (1, 2 mg/kg), Agmatine (5, 10 mg/kg) and 2 groups of agmatine (5, 10 mg/kg) with higher doses of METH (2 mg/kg) for 5 consecutive days (n = 8 in each group). All injections were done intraperitoneally and agmatine was administrated 10 min before METH treatment. Furthermore, Passive avoidance learning (PAL) test was assessed on the 5th day. Retention test was done 24 h after training and the rats were sacrificed immediately. Hippocampi were removed and stored at -80 °C. Finally, hippocampal CaMKII-α gene expression was measured using Quantitative Real-time PCR. Our data showed that chronic METH dose-dependently impaired PAL retrieval, as it decreased step-through latency (STL) and increased time spent in the dark compartment (TDC). While Agmatine with a higher dose (10 mg/kg) significantly decreased impairment effect of METH (2 mg/kg) on PAL and memory. Also, molecular results revealed that METH (2 mg/kg) markedly decreased hippocampal CaMKII-α gene expression while agmatine (10 mg/kg) co-adminstration prevented it. Taken together, the results propose that agmatine may provide a potential therapy for learning and memory deficits induced by METH.

Are ecstasy induced serotonergic alterations overestimated for the majority of users?

BACKGROUND

Neuroimaging studies imply that the regular use of ±3,4-methylenedioxymethamphetamine (MDMA), the major constituent of ecstasy pills, alters the brain's serotonergic system in a dose-dependent manner. However, the relevance of these findings remains unclear due to limited knowledge about the ecstasy/MDMA use pattern of real-life users.

AIMS

We examined the representativeness of ecstasy users enrolled in neuroimaging studies by comparing their ecstasy use habits with the use patterns of a large, international sample.

METHODS

A systematic literature search revealed 10 imaging studies that compare serotonin transporter levels in recreational ecstasy users to matched controls. To characterize the ecstasy use patterns we relied on the Global Drug Survey, the world's largest self-report database on drug use. The basis of the dose comparison were the Usual Amount (pills/session), Use Frequency (sessions/month) and Dose Intensity (pills/year) variables.

RESULTS

Both the average Usual Amount (pills/session) and Use Frequency (sessions/month) of neuroimaging study participants corresponded to the top 5-10% of the Global Drug Survey sample and imaging participants, on average, consumed 720% more pills over a year than the Global Drug Survey participants.

CONCLUSIONS

Our findings suggest that the serotonin brain imaging literature has focused on unusually heavy ecstasy use and therefore the conclusions from these studies are likely to overestimate the extent of serotonergic alterations experienced by the majority of people who use ecstays.

Differential effects of MDMA and cocaine on inhibitory avoidance and object recognition tests in rodents

INTRODUCTION

Drug addiction continues being a major public problem faced by modern societies with different social, health and legal consequences for the consumers. Consumption of psychostimulants, like cocaine or MDMA (known as ecstasy) are highly prevalent and cognitive and memory impairments have been related with the abuse of these drugs.

AIM

The aim of this work was to review the most important data of the literature in the last 10 years about the effects of cocaine and MDMA on inhibitory avoidance and object recognition tests in rodents.

DEVELOPMENT

The object recognition and the inhibitory avoidance tests are popular procedures used to assess different types of memory. We compare the effects of cocaine and MDMA administration in these tests, taking in consideration different factors such as the period of life development of the animals (prenatal, adolescence and adult age), the presence of polydrug consumption or the role of environmental variables. Brain structures involved in the effects of cocaine and MDMA on memory are also described.

CONCLUSIONS

Cocaine and MDMA induced similar impairing effects on the object recognition test during critical periods of lifetime or after abstinence of prolonged consumption in adulthood. Deficits of inhibitory avoidance memory are observed only in adult rodents exposed to MDMA. Psychostimulant abuse is a potential factor to induce memory impairments and could facilitate the development of future neurodegenerative disorders.

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.

Neurochemical substrates of the rewarding effects of MDMA: implications for the development of pharmacotherapies to MDMA dependence

In recent years, studies with animal models of reward, such as the intracranial self-stimulation, self-administration, and conditioned place preference paradigms, have increased our knowledge on the neurochemical substrates of the rewarding effects of 3,4-methylenedioxymetamphetamine (MDMA) in rodents. However, pharmacological and neuroimaging studies with human participants are scarce. Serotonin [5-hydroxytryptamine (5-HT)], dopamine (DA), endocannabinoids, and endogenous opiates are the main neurotransmitter systems involved in the rewarding effects of MDMA in rodents, but other neurotransmitters such as glutamate, acetylcholine, adenosine, and neurotensin are also involved. The most important finding of recent research is the demonstration of differential involvement of specific neurotransmitter receptor subtypes (5-HT2, 5-HT3, DA D1, DA D2, CB1, μ and δ opioid, etc.) and extracellular proteins (DA and 5-HT transporters) in the acquisition, expression, extinction, and reinstatement of MDMA self-administration and conditioned place preference. It is important to extend the research on the effects of different compounds acting on these receptors/transporters in animal models of reward, especially in priming-induced, cue-induced, and stress-induced reinstatement. Increase in knowledge of the neurochemical substrates of the rewarding effects of MDMA may contribute to the design of new pharmacological treatments for individuals who develop MDMA dependence.

Opioid gene expression changes and post-translational histone modifications at promoter regions in the rat nucleus accumbens after acute and repeated 3,4-methylenedioxy-methamphetamine (MDMA) exposure

The recreational drug of abuse 3,4-methylenedioxymethamphetamine (MDMA) has been shown to produce neurotoxic damage and long-lasting changes in several brain areas. In addition to the involvement of serotoninergic and dopaminergic systems, little information exists about the contribution of nociceptin/orphaninFQ (N/OFQ)-NOP and dynorphin (DYN)-KOP systems in neuronal adaptations evoked by MDMA. Here we investigated the behavioral and molecular effects induced by acute (8mg/kg) or repeated (8mg/kg twice daily for seven days) MDMA exposure. MDMA exposure affected body weight gain and induced hyperlocomotion; this latter effect progressively decreased after repeated administration. Gene expression analysis indicated a down-regulation of the N/OFQ system and an up-regulation of the DYN system in the nucleus accumbens (NAc), highlighting an opposite systems regulation in response to MDMA exposure. Since histone modifications have been strongly associated to the addiction-related maladaptive changes, we examined two permissive (acH3K9 and me3H3K4) and two repressive transcription marks (me3H3K27 and me2H3K9) at the pertinent opioid gene promoter regions. Chromatin immunoprecipitation assays revealed that acute MDMA increased me3H3K4 at the pN/OFQ, pDYN and NOP promoters. Following acute and repeated treatment a significant decrease of acH3K9 at the pN/OFQ promoter was observed, which correlated with gene expression results. Acute treatment caused an acH3K9 increase and a me2H3K9 decrease at the pDYN promoter which matched its mRNA up-regulation. Our data indicate that the activation of the DYNergic stress system together with the inactivation of the N/OFQergic anti-stress system contribute to the neuroadaptive actions of MDMA and offer novel epigenetic information associated with MDMA abuse.

Investigation of the mechanisms mediating MDMA "Ecstasy"-induced increases in cerebro-cortical perfusion determined by btASL MRI

RATIONALE

Acute administration of the recreational drug of abuse 3,4-methylenedioxymethamphetamine (MDMA; Ecstasy) has previously been shown to increase cerebro-cortical perfusion as determined by bolus-tracking arterial spin labelling (btASL) MRI.

OBJECTIVES

The purpose of the current study was to assess the mechanisms mediating these changes following systemic administration of MDMA to rats.

METHODS

Pharmacological manipulation of serotonergic, dopaminergic and nitrergic transmission was carried out to determine the mechanism of action of MDMA-induced increases in cortical perfusion using btASL MRI.

RESULTS

Fenfluramine (10 mg/kg), like MDMA (20 mg/kg), increased cortical perfusion. Increased cortical perfusion was not obtained with the 5-HT2 receptor agonist 2,5-dimethoxy-4-iodophenyl-aminopropane hydrochloride (DOI) (1 mg/kg). Depletion of central 5-HT following systemic administration of the tryptophan hydroxylase inhibitor para-chlorophenylalanine (pCPA) produced effects similar to those observed with MDMA. Pre-treatment with the 5-HT receptor antagonist metergoline (4 mg/kg) or with the 5-HT reuptake inhibitor citalopram (30 mg/kg), however, failed to produce any effect alone or influence the response to MDMA. Pre-treatment with the dopamine D1 receptor antagonist SCH 23390 (1 mg/kg) failed to influence the changes in cortical perfusion obtained with MDMA. Treatment with the neuronal nitric oxide (NO) synthase inhibitor 7-nitroindazole (7-NI) (25 mg/kg) provoked no change in cerebral perfusion alone yet attenuated the MDMA-related increase in cortical perfusion.

CONCLUSIONS

Cortical 5-HT depletion is associated with increases in perfusion although this mechanism alone does not account for MDMA-related changes. A role for NO, a key regulator of cerebrovascular perfusion, is implicated in MDMA-induced increases in cortical perfusion.

The heat is on: Molecular mechanisms of drug-induced hyperthermia

Thermoregulation is an essential homeostatic process in which critical mechanisms of heat production and dissipation are controlled centrally in large part by the hypothalamus and peripherally by activation of the sympathetic nervous system. Drugs that disrupt the components of this highly orchestrated multi-organ process can lead to life-threatening hyperthermia. In most cases, hyperthermic agents raise body temperature by increasing the central and peripheral release of thermoregulatory neurotransmitters that ultimately lead to heat production in thermogenic effector organs skeletal muscle (SKM) and brown adipose tissue (BAT). In many cases hyperthermic drugs also decrease heat dissipation through peripheral changes in blood flow. Drug-induced heat production is driven by the stimulation of mechanisms that normally regulate the adaptive thermogenic responses including both shivering and non-shivering thermogenesis (NST) mechanisms. Modulation of the mitochondrial electrochemical proton/pH gradient by uncoupling protein 1 (UCP1) in BAT is the most well characterized mechanism of NST in response to cold, and may contribute to thermogenesis induced by sympathomimetic agents, but this is far from established. However, the UCP1 homologue, UCP3, and the ryanodine receptor (RYR1) are established mediators of toxicant-induced hyperthermia in SKM. Defining the molecular mechanisms that orchestrate drug-induced hyperthermia will be essential in developing treatment modalities for thermogenic illnesses. This review will briefly summarize mechanisms of thermoregulation and provide a survey of pharmacologic agents that can lead to hyperthermia. We will also provide an overview of the established and candidate molecular mechanisms that regulate the actual thermogenic processes in heat effector organs BAT and SKM.

3,4-methylenedioxymethamphetamine (MDMA): current perspectives

Ecstasy is a widely used recreational drug that usually consists primarily of 3,4-methylenedioxymethamphetamine (MDMA). Most ecstasy users consume other substances as well, which complicates the interpretation of research in this field. The positively rated effects of MDMA consumption include euphoria, arousal, enhanced mood, increased sociability, and heightened perceptions; some common adverse reactions are nausea, headache, tachycardia, bruxism, and trismus. Lowering of mood is an aftereffect that is sometimes reported from 2 to 5 days after a session of ecstasy use. The acute effects of MDMA in ecstasy users have been attributed primarily to increased release and inhibited reuptake of serotonin (5-HT) and norepinephrine, along with possible release of the neuropeptide oxytocin. Repeated or high-dose MDMA/ecstasy use has been associated with tolerance, depressive symptomatology, and persisting cognitive deficits, particularly in memory tests. Animal studies have demonstrated that high doses of MDMA can lead to long-term decreases in forebrain 5-HT concentrations, tryptophan hydroxylase activity, serotonin transporter (SERT) expression, and visualization of axons immunoreactive for 5-HT or SERT. These neurotoxic effects may reflect either a drug-induced degeneration of serotonergic fibers or a long-lasting downregulation in 5-HT and SERT biosynthesis. Possible neurotoxicity in heavy ecstasy users has been revealed by neuroimaging studies showing reduced SERT binding and increased 5-HT_2A receptor binding in several cortical and/or subcortical areas. MDMA overdose or use with certain other drugs can also cause severe morbidity and even death. Repeated use of MDMA may lead to dose escalation and the development of dependence, although such dependence is usually not as profound as is seen with many other drugs of abuse. MDMA/ecstasy-dependent patients are treated with standard addiction programs, since there are no specific programs for this substance and no proven medications. Finally, even though MDMA is listed as a Schedule I compound by the Drug Enforcement Agency, MDMA-assisted psychotherapy for patients with chronic, treatment-resistant posttraumatic stress disorder is currently under investigation. Initial results show efficacy for this treatment approach, although considerably more research must be performed to confirm such efficacy and to ensure that the benefits of MDMA-assisted therapy outweigh the risks to the patients.

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.

3,4-methylenedioxymethamphetamine induces gene expression changes in rats related to serotonergic and dopaminergic systems, but not to neurotoxicity

3,4-Methylenedioxymethamphetamine (MDMA, ecstasy) is an amphetamine derivative widely abused by young adults. Although many studies have reported that relatively high doses of MDMA deplete serotonin (5-HT) content and decrease the availability of serotonin transporters (5-HTT), limited evidence is available as to the adaptive mechanisms taking place in gene expression levels in the brain following a dosing regimen of MDMA comparable to human consumption. In order to further clarify this issue, we used quantitative PCR to study the long-term changes induced by acute administration of MDMA (5 mg/kg × 3) in the expression of genes related to serotonergic and dopaminergic systems, as well as those related to cellular toxicity in the cortex, hippocampus, striatum, and brain stem of rats. Seven days after MDMA administration, we found a significantly lower expression of the 5-HTT (Slc6a4) and the vesicular monoamine transporter (Slc18a2) genes in the brain stem area. In the hippocampus, monoamine oxidase B (Maob) and tryptophan hydroxylase 2 (Tph2) gene expressions were increased. In the striatum, tyrosine hydroxylase (Th) expression was decreased, and a lower expression of α-synuclein (Snca) was observed in the cortex. In contrast, no significant changes were observed in the genes considered to be biomarkers of toxicity including the glial fibrillary acidic protein (Gfap) and the heat-shock 70 kD protein 1A (Hspa1a) in any of the structures assayed. These results suggest that MDMA promotes adaptive changes in genes related to serotonergic and dopaminergic functionality, but not in genes related to neurotoxicity.

Effects of combined treatment with mephedrone and methamphetamine or 3,4-methylenedioxymethamphetamine on serotonin nerve endings of the hippocampus

AIMS

Mephedrone is a stimulant drug of abuse with close structural and mechanistic similarities to methamphetamine and 3,4-methylenedioxymethamphetamine (MDMA). Although mephedrone does not damage dopamine nerve endings it increases the neurotoxicity of amphetamine, methamphetamine and MDMA. The effects of mephedrone on serotonin (5HT) nerve endings are not fully understood, with some investigators reporting damage while others conclude it does not. Presently, we investigate if mephedrone given alone or with methamphetamine or MDMA damages 5HT nerve endings of the hippocampus.

MAIN METHODS

The status of 5HT nerve endings in the hippocampus of female C57BL mice was assessed through measures of 5HT by HPLC and by immunoblot analysis of serotonin transporter (SERT) and tryptophan hydroxylase 2 (TPH2), selective markers of 5HT nerve endings. Astrocytosis was assessed through measures of glial fibrillary acidic protein (GFAP) (immunoblotting) and microglial activation was determined by histochemical staining with Isolectin B4.

KEY FINDINGS

Mephedrone alone did not cause persistent reductions in the levels of 5HT, SERT or TPH2. Methamphetamine and MDMA alone caused mild reductions in 5HT but did not change SERT and TPH2 levels. Combined treatment with mephedrone and methamphetamine or MDMA did not change the status of 5HT nerve endings to an extent that was different from either drug alone.

SIGNIFICANCE

Mephedrone does not cause toxicity to 5HT nerve endings of the hippocampus. When co-administered with methamphetamine or MDMA, drugs that are often co-abused with mephedrone by humans, toxicity is not increased as is the case for dopamine nerve endings when these drugs are taken together.

Age differences in (±) 3,4-methylenedioxymethamphetamine (MDMA)-induced conditioned taste aversions and monoaminergic levels

Preclinical work indicates that adolescent rats appear more sensitive to the rewarding effects and less sensitive to the aversive effects of abused drugs. The present investigation utilized the conditioned taste aversion (CTA) design to measure the relative aversive effects of (±)3,4-methylenedioxymethamphetamine (MDMA; 0, 1.0, 1.8, or 3.2 mg/kg) in adolescent and adult Sprague-Dawley rats. After behavioral testing was complete, monoamine and associated metabolite levels in discrete brain regions were quantified using high-performance liquid chromatography coupled to electrochemical detection (HPLC-ECD) to determine if adolescent animals displayed a different neurochemical profile than did adult animals after being exposed to subcutaneous low doses of MDMA. Adolescent rats displayed less robust MDMA-induced taste aversions than adults during acquisition and on a final two-bottle aversion test. MDMA at these doses had no consistent effect on monoamine levels in either age group, although levels did vary with age. The relative insensitivity of adolescents to MDMA's aversive effects may engender an increased vulnerability to MDMA abuse in this specific population.

3,4-Methylenedioxymethamphetamine induces a hyperthermic and hypermetabolic crisis in pigs with and without a genetic disposition for malignant hyperthermia

BACKGROUND

Clinical symptoms of acute 3,4-methylenedioxymethamphetamine (MDMA) intoxication and malignant hyperthermia have many similarities. At present, however, there is contradictory evidence concerning the malignant hyperthermia trigger potency of MDMA.

OBJECTIVE

This study was designed to investigate whether MDMA has malignant hyperthermia trigger potential and leads to malignant hyperthermia in pigs with or without a genetic predisposition to the condition. In addition, the therapeutic effectiveness of a new dantrolene sodium suspension was examined.

DESIGN

Experimental study, using an animal model of Piétrain pigs.

SETTINGS

Institute for Research in Operative Medicine, University of Witten/Herdecke, Hospital Cologne Merheim, Cologne, Germany, October 2006 to February 2007. Trigger-free anaesthesia was performed on seven malignant hyperthermia-susceptible and six malignant hyperthermia-normal Piétrain pigs, and cumulative doses of MDMA were administered to each animal.

INTERVENTIONS

After achieving predefined malignant hyperthermia criteria, standardised therapy was initiated; dantrolene sodium suspension (5 mg kg(-1)) was administered and the injection was repeated after 24 min.

MAIN OUTCOME MEASURES

The malignant hyperthermia trigger potency of MDMA was analysed by monitoring pH, PaCO2 and temperature. In addition, concentrations of thyroid hormone, mitochondrial uncoupling protein 3, noradrenaline and free fatty acids during administration of MDMA and dantrolene sodium suspension were analysed.

RESULTS

MDMA administration led to fulminant hypermetabolic and hyperthermic responses in malignant hyperthermia-susceptible and malignant hyperthermia-normal pigs, with significant decreases in pH (susceptible: pH 7.21 ± 0.11, normal: pH 7.21 ± 0.07), severe hypercapnia (susceptible: paCO2 10.3 ± 3.5 kPa, normal: paCO2 9.8 ± 1.7 kPa), and hyperthermia (susceptible: 40.6 ± 2.0°C, normal: 40.1 ± 0.4°C). There were no significant differences in changes in clinical and laboratory variables between groups. The dantrolene therapy regimen was effective in treating the MDMA-induced metabolic crises.

CONCLUSION

MDMA is not a classic trigger for the development of malignant hyperthermia reactions in pigs. MDMA intoxication leads to severe, long-lasting hyperthermia and hypermetabolism in both malignant hyperthermia-susceptible and hyperthermia-normal pigs, with life-threatening malignant hyperthermia-like symptoms which are responsive to supportive treatment and dantrolene sodium suspension.

Effects of repeated treatment with MDMA on working memory and behavioural flexibility in mice

Repeated administration of 3,4-methylenedioxymethamphetamine (MDMA) produces dopaminergic neurotoxicity in mice. However, it is still not clear whether this exposure induces deficits in cognitive processing related to specific subsets of executive functioning. We evaluated the effects of neurotoxic and non-neurotoxic doses of MDMA (0, 3 and 30 mg/kg, twice daily for 4 days) on working memory and attentional set-shifting in mice, and changes in extracellular levels of dopamine (DA) in the striatum. Treatment with MDMA (30 mg/kg) disrupted performance of acquired operant alternation, and this impairment was still apparent 5 days after the last drug administration. Decreased alternation was not related to anhedonia because no differences were observed between groups in the saccharin preference test under similar experimental conditions. Correct responding on delayed alternation was increased 1 day after repeated treatment with MDMA (30 mg/kg), probably because of general behavioural quiescence. Notably, the high dose regimen of MDMA impaired attentional set-shifting related to an increase in total perseveration errors. Finally, basal extracellular levels of DA in the striatum were not modified in mice repeatedly treated with MDMA with respect to controls. However, an acute challenge with MDMA (10 mg/kg) failed to increase DA outflow in mice receiving the highest MDMA dose (30 mg/kg), corroborating a decrease in the functionality of DA transporters. Seven days after this treatment, the effects of MDMA on DA outflow were recovered. These results suggest that repeated neurotoxic doses of MDMA produce lasting impairments in recall of alternation behaviour and reduce cognitive flexibility in mice.

5-Iodo-2-aminoindan (5-IAI): chemistry, pharmacology, and toxicology of a research chemical producing MDMA-like effects

In 2010, an internet snapshot of EMCDDA anticipated the presence of 5-iodo-2-aminoindan (5-IAI) within the recreational drug market. In 2011, this compound, a psychoactive derivative of 2-aminoindane, was identified in recreational products sold in the United Kingdom. 5-IAI is a rigid analogue of p-iodoamphetamine producing MDMA-like effects. The aim of this paper is to summarize the clinical, pharmacological, and toxicological information about this new potential drug of abuse.

Effects of a short-course MDMA binge on dopamine transporter binding and on levels of dopamine and its metabolites in adult male rats

Although the recreational drug 3,4-methylenedioxymethamphetamine (MDMA) is often described as a selective serotonergic neurotoxin, some research has challenged this view. The objective of this study was to determine the influence of MDMA on subsequent levels of two different markers of dopaminergic function, the dopamine transporter (DAT) as well as dopamine and its major metabolites. In experiment I, adult male Sprague-Dawley rats were administered either a low or moderate dose MDMA binge (2.5 or 5.0mg/kg×4 with an inter-dose interval of 1h) or saline, and were killed 1 week later. The moderate dose dramatically reduced [(3)H]WIN 35,428 binding to striatal DAT by 73.7% (P≤0.001). In experiment II, animals were binged with a higher dose of MDMA (10mg/kg×4) to determine the drug's effects on concentrations of serotonin (5-HT), dopamine, and their respective major metabolites 5-hydroxyindoleacetic acid (5-HIAA), dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) in the striatum and frontal cortex 1 week later. As expected, MDMA significantly reduced 5-HT and 5-HIAA (≥50%) in these structures, while only a marginal decrease in dopamine was noted in the striatum. In contrast, levels of DOPAC (34.3%, P<0.01) and HVA (33.5%, P<0.001) were reduced by MDMA treatment, suggesting a decrease in dopamine turnover. Overall, these findings indicate that while serotonergic markers are particularly vulnerable to MDMA-induced depletion, significant dopaminergic deficits may also occur under some conditions. Importantly, DAT expression may be more vulnerable to perturbation by MDMA than dopamine itself.

The nucleus accumbens 5-HTR₄-CART pathway ties anorexia to hyperactivity

In mental diseases, the brain does not systematically adjust motor activity to feeding. Probably, the most outlined example is the association between hyperactivity and anorexia in Anorexia nervosa. The neural underpinnings of this 'paradox', however, are poorly elucidated. Although anorexia and hyperactivity prevail over self-preservation, both symptoms rarely exist independently, suggesting commonalities in neural pathways, most likely in the reward system. We previously discovered an addictive molecular facet of anorexia, involving production, in the nucleus accumbens (NAc), of the same transcripts stimulated in response to cocaine and amphetamine (CART) upon stimulation of the 5-HT(4) receptors (5-HTR(4)) or MDMA (ecstasy). Here, we tested whether this pathway predisposes not only to anorexia but also to hyperactivity. Following food restriction, mice are expected to overeat. However, selecting hyperactive and addiction-related animal models, we observed that mice lacking 5-HTR(1B) self-imposed food restriction after deprivation and still displayed anorexia and hyperactivity after ecstasy. Decryption of the mechanisms showed a gain-of-function of 5-HTR(4) in the absence of 5-HTR(1B), associated with CART surplus in the NAc and not in other brain areas. NAc-5-HTR(4) overexpression upregulated NAc-CART, provoked anorexia and hyperactivity. NAc-5-HTR(4) knockdown or blockade reduced ecstasy-induced hyperactivity. Finally, NAc-CART knockdown suppressed hyperactivity upon stimulation of the NAc-5-HTR(4). Additionally, inactivating NAc-5-HTR(4) suppressed ecstasy's preference, strengthening the rewarding facet of anorexia. In conclusion, the NAc-5-HTR(4)/CART pathway establishes a 'tight-junction' between anorexia and hyperactivity, suggesting the existence of a primary functional unit susceptible to limit overeating associated with resting following homeostasis rules.

Role of the dopaminergic system in the acquisition, expression and reinstatement of MDMA-induced conditioned place preference in adolescent mice

Background

The rewarding effects of 3,4-methylenedioxy-metamphetamine (MDMA) have been demonstrated in conditioned place preference (CPP) procedures, but the involvement of the dopaminergic system in MDMA-induced CPP and reinstatement is poorly understood.

Methodology/Principal Findings

In this study, the effects of the DA D1 antagonist SCH 23390 (0.125 and 0.250 mg/kg), the DA D2 antagonist Haloperidol (0.1 and 0.2 mg/kg), the D2 antagonist Raclopride (0.3 and 0.6 mg/kg) and the dopamine release inhibitor CGS 10746B (3 and 10 mg/kg) on the acquisition, expression and reinstatement of a CPP induced by 10 mg/kg of MDMA were evaluated in adolescent mice. As expected, MDMA significantly increased the time spent in the drug-paired compartment during the post-conditioning (Post-C) test, and a priming dose of 5 mg/kg reinstated the extinguished preference. The higher doses of Haloperidol, Raclopride and CGS 10746B and both doses of SCH 23390 blocked acquisition of the MDMA-induced CPP. However, only Haloperidol blocked expression of the CPP. Reinstatement of the extinguished preference was not affected by any of the drugs studied. Analysis of brain monoamines revealed that the blockade of CPP acquisition was accompanied by an increase in DA concentration in the striatum, with a concomitant decrease in DOPAC and HVA levels. Administration of haloperidol during the Post-C test produced increases in striatal serotonin, DOPAC and HVA concentrations. In mice treated with the higher doses of haloperidol and CGS an increase in SERT concentration in the striatum was detected during acquisition of the CPP, but no changes in DAT were observed.

Conclusions/Significance

These results demonstrate that, in adolescent mice, the dopaminergic system is involved in the acquisition and expression of MDMA-induced CPP, but not in its reinstatement.

Acutely applied MDMA enhances long-term potentiation in rat hippocampus involving D1/D5 and 5-HT2 receptors through a polysynaptic mechanism

3,4-Methylenedioxymethamphetamine (MDMA, ecstasy) is a drug of abuse that induces learning and memory deficit. However, there are no experimental data that correlate the behavioral evidence with models of synaptic plasticity such as long-term potentiation (LTP) or long-term depression (LTD). Using field potential recordings in rat hippocampal slices of young rats, we found that acute application of MDMA enhances LTP in CA3-CA1 synapses without affecting LTD. Using specific antagonists and paired-pulse facilitation protocols we observed that the MDMA-dependent increase of LTP involves presynaptic 5-HT₂ serotonin receptors and postsynaptic D1/D5 dopamine receptors. In addition, the inhibition of PKA suppresses the MDMA-dependent increase in LTP, suggesting that dopamine receptor agonism activates cAMP-dependent intracellular pathways. We propose that MDMA exerts its LTP-altering effect involving a polysynaptic interaction between serotonergic and dopaminergic systems in hippocampal synapses. Our results are compatible with the view that the alterations in hippocampal LTP could be responsible for MDMA-dependent cognitive deficits observed in humans and animals.

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.

Adolescent pre-exposure to ethanol and 3,4-methylenedioxymethylamphetamine (MDMA) increases conditioned rewarding effects of MDMA and drug-induced reinstatement

Many adolescents often take ethanol (EtOH) in combination with 3,4-methylenedioxymethylamphetamine (MDMA). In the present work, we used a mouse model to study the effect of repeated pre-exposure during adolescence to EtOH (2 g/kg), MDMA (10 or 20 mg/kg) or EtOH + MDMA on the rewarding and reinstating effects of MDMA in the conditioned place preference (CPP) paradigm. Pre-exposure to EtOH, MDMA or both increased the rewarding effects of a low dose of MDMA (1.25 mg/kg). These pre-treatments did not affect the acquisition of the CPP induced by 5 mg/kg of MDMA. However, the CPP was more persistent in mice pre-exposed to both doses of MDMA or to EtOH + MDMA20. After extinction of the CPP induced by 5 mg/kg of MDMA, reinstatement was observed in all groups with a priming dose of 2.5 mg/kg of MDMA, in the groups pre-exposed to EtOH or MDMA alone with a priming dose of 1.25 mg/kg, and in the groups pre-treated with MDMA alone with a priming dose of 0.625 mg/kg. Pre-treatment during adolescence with MDMA or EtOH induced long-term changes in the level of biogenic amines [dihydroxyphenyl acetic acid, homovanillic acid, dopamine turnover, serotonin (5-hydroxytryptamine, 5-HT) and 5-hydroxyindole acetic acid (5-HIAA) in the striatum, and 5-HT and 5-HIAA in the cortex] after the first reinstatement test, although these effects depended on the dose used during conditioning. These results suggest that exposure to EtOH and MDMA during adolescence reinforces the addictive properties of MDMA.

Effects of exposure to amphetamine derivatives on passive avoidance performance and the central levels of monoamines and their metabolites in mice: correlations between behavior and neurochemistry

RATIONALE

Considerable evidence indicates that amphetamine derivatives can deplete brain monoaminergic neurotransmitters. However, the behavioral and cognitive consequences of neurochemical depletions induced by amphetamines are not well established.

OBJECTIVES

In this study, mice were exposed to dosing regimens of 3,4-methylenedioxymethamphetamine (MDMA), methamphetamine (METH), or parachloroamphetamine (PCA) known to deplete the monoamine neurotransmitters dopamine and serotonin, and the effects of these dosing regimens on learning and memory were assessed.

METHODS

In the same animals, we determined deficits in learning and memory via passive avoidance (PA) behavior and changes in tissue content of monoamine neurotransmitters and their primary metabolites in the striatum, frontal cortex, cingulate, hippocampus, and amygdala via ex vivo high-pressure liquid chromatography.

RESULTS

Exposure to METH and PCA impaired PA performance and resulted in significant depletions of dopamine, serotonin, and their metabolites in several brain regions. Multiple linear regression analysis revealed that the tissue concentration of dopamine in the anterior striatum was the strongest predictor of PA performance, with an additional significant contribution by the tissue concentration of the serotonin metabolite 5-hydroxyindoleacetic acid in the cingulate. In contrast to the effects of METH and PCA, exposure to MDMA did not deplete anterior striatal dopamine levels or cingulate levels of 5-hydroxyindoleacetic acid, and it did not impair PA performance.

CONCLUSIONS

These studies demonstrate that certain amphetamines impair PA performance in mice and that these impairments may be attributable to specific neurochemical depletions.

Electroencephalographic and convulsive effects of binge doses of (+)-methamphetamine, 5-methoxydiisopropyltryptamine, and (±)-3,4-methylenedioxymethamphetamine in rats

The abuse of drugs such as methamphetamine (MA), 3,4-methylenedioxymethamphetamine (Ecstasy, MDMA), and 5-methoxydiisopropyltryptamine (5-MeO-DIPT; Foxy) is global. Symptoms from taking these drugs include tachycardia, agitation, hyperpyrexia, and sometimes seizures. We compared the EEG effects of these drugs in male Sprague-Dawley rats (~300 g) implanted with cortical electroencephalographic (EEG) electrodes prior to testing. Animals received four subcutaneous injections of MA, MDMA, or Foxy (10 mg/kg each as freebase, administered every 2 h), or saline as these doses produce lasting effects on learning, memory, and monoamines. EEG tracings were recorded before, during, and after treatment. Animals receiving MDMA showed no significant EEG abnormalities or myoclonus. MA treatment resulted in myoclonic activity and in brief (<10 s) EEG epileptiform activity in ~50% of the rats. Longer seizure activity (10 s to 5 min) was recorded in some MA-treated rats following the third and fourth doses. The onset of myoclonic activity following Foxy treatment occurred shortly after the first dose. All rats receiving Foxy showed seizures by the second dose and this continued throughout the treatment regimen. The results show that binge doses of MA and MDMA, which mimic the neurochemical changes seen in chronic users, increase EEG abnormalities after MA but not after MDMA. While the neurochemical effects of Foxy are not known in humans, this drug causes severe EEG abnormalities and overt seizures in 100% of tested animals.

Genetic deletion of trace amine 1 receptors reveals their role in auto-inhibiting the actions of ecstasy (MDMA)

"Ecstasy" [3,4-methylenedioxymetamphetamine (MDMA)] is of considerable interest in light of its prosocial properties and risks associated with widespread recreational use. Recently, it was found to bind trace amine-1 receptors (TA(1)Rs), which modulate dopaminergic transmission. Accordingly, using mice genetically deprived of TA(1)R (TA(1)-KO), we explored their significance to the actions of MDMA, which robustly activated human adenylyl cyclase-coupled TA(1)R transfected into HeLa cells. In wild-type (WT) mice, MDMA elicited a time-, dose-, and ambient temperature-dependent hypothermia and hyperthermia, whereas TA(1)-KO mice displayed hyperthermia only. MDMA-induced increases in dialysate levels of dopamine (DA) in dorsal striatum were amplified in TA(1)-KO mice, despite identical levels of MDMA itself. A similar facilitation of the influence of MDMA upon dopaminergic transmission was acquired in frontal cortex and nucleus accumbens, and induction of locomotion by MDMA was haloperidol-reversibly potentiated in TA(1)-KO versus WT mice. Conversely, genetic deletion of TA(1)R did not affect increases in DA levels evoked by para-chloroamphetamine (PCA), which was inactive at hTA(1) sites. The TA(1)R agonist o-phenyl-3-iodotyramine (o-PIT) blunted the DA-releasing actions of PCA both in vivo (dialysis) and in vitro (synaptosomes) in WT but not TA(1)-KO animals. MDMA-elicited increases in dialysis levels of serotonin (5-HT) were likewise greater in TA(1)-KO versus WT mice, and 5-HT-releasing actions of PCA were blunted in vivo and in vitro by o-PIT in WT mice only. In conclusion, TA(1)Rs exert an inhibitory influence on both dopaminergic and serotonergic transmission, and MDMA auto-inhibits its neurochemical and functional actions by recruitment of TA(1)R. These observations have important implications for the effects of MDMA in humans.

Pharmacodynamic interactions between MDMA and concomitants in MDMA tablets on extracellular dopamine and serotonin in the rat brain

3,4-methylenedioxymethamphetamine (MDMA) is a psychoactive stimulant abused by young people as the recreational drug ecstasy. Other compounds, either deliberately added or present as byproducts, are often found in MDMA tablets and can unexpectedly interact with each other. The aim of this study was to evaluate the pharmacodynamic effects of interactions caused by concomitants in MDMA tablets on extracellular dopamine and serotonin (5-HT) by microdialysis in the striatum of ethylcarbamate-anesthetized rats. Baseline levels of dopamine and 5-HT in the striatum were 16.5±7.7 and 3.5±1.7 nM (mean±standard deviation), respectively. After a single administration of MDMA (10 mg/kg, i.p.), a dramatic increase in extracellular dopamine (Cmax: 36.1-fold vs. baseline) and 5-HT levels (Cmax: 9.3-fold vs. baseline) was observed. When rats were co-administered with methamphetamine (1, 5 or 10 mg/kg) with MDMA, the dopamine levels induced by MDMA increased in a methamphetamine-dose-dependent manner (Cmax: 2.5-, 3.5-, and 3.8-fold vs. MDMA). A similar trend was observed in 5-HT levels (Cmax: 1.1-, 1.3-, and 1.8-fold vs. MDMA). In contrast, ketamine and caffeine showed synergistic effects on the monoamine levels induced by MDMA, whereas the individual administration of either of these compounds did not affect monoamine levels. Ketamine (1, 5 mg/kg) decreased the dopamine levels induced by MDMA (Cmax: 0.9- and 0.7-fold vs. MDMA) and increased the 5-HT levels induced by MDMA (Cmax: 1.4- and 1.6-fold vs. MDMA), and co-administration of caffeine (20 mg/kg) with MDMA increased dopamine levels (Cmax: 1.7-fold vs. MDMA). These results suggest that exposure to multiple drugs in addition to MDMA can have neurotoxic effects.

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.

Acute psychomotor, memory and subjective effects of MDMA and THC co-administration over time in healthy volunteers

In Western societies a considerable percentage of young people expose themselves to the combination of 3,4-methylenedioxymethamphetamine (MDMA or 'ecstasy') and cannabis. The aim of the present study was to assess the acute effects of co-administration of MDMA and THC (the main psychoactive compound of cannabis) on pharmacokinetics, psychomotor performance, memory and subjective experience over time. We performed a four-way, double blind, randomized, crossover, placebo-controlled study in 16 healthy volunteers (12 male, four female) between the ages of 18 and 27. MDMA (100 mg) was given orally, THC (4, 6, and 6 mg, interval of 90 min) was vaporized and inhaled. THC induced more robust cognitive impairment compared with MDMA, and co-administration did not exacerbate single drug effects on cognitive function. However, co-administration of THC with MDMA increased desired subjective drug effects and drug strength compared with the MDMA condition, which may explain the widespread use of this combination.

Persistent nigrostriatal dopaminergic abnormalities in ex-users of MDMA ('Ecstasy'): an 18F-dopa PET study

Ecstasy (±3,4-methylenedioxymethamphetamine, MDMA) is a popular recreational drug with known serotonergic neurotoxicity. Its long-term effects on dopaminergic function are less certain. Studying the long-term effects of ecstasy is often confounded by concomitant polydrug use and the short duration of abstinence. We used (18)F-dopa positron emission tomography (PET) to investigate the long-term effects of ecstasy on nigrostriatal dopaminergic function in a group of male ex-recreational users of ecstasy who had been abstinent for a mean of 3.22 years. We studied 14 ex-ecstasy users (EEs), 14 polydrug-using controls (PCs) (matched to the ex-users for other recreational drug use), and 12 drug-naive controls (DCs). Each participant underwent one (18)F-dopa PET, cognitive assessments, and hair and urinary analyses to corroborate drug-use history. The putamen (18)F-dopa uptake of EEs was 9% higher than that of DCs (p=0.021). The putamen uptake rate of PCs fell between the other two groups, suggesting that the hyperdopaminergic state in EEs may be due to the combined effects of ecstasy and polydrug use. There was no relationship between the amount of ecstasy used and striatal (18)F-dopa uptake. Increased putaminal (18)F-dopa uptake in EEs after an abstinence of >3 years (mean) suggests that the effects are long lasting. Our findings suggest potential long-term effects of ecstasy use, in conjunction with other recreational drugs, on nigrostriatal dopaminergic functions. Further longitudinal studies are required to elucidate the significance of these findings as they may have important public health implications.