Stereochemical effects of 3,4-methylenedioxymethamphetamine (MDMA) and related amphetamine derivatives on inhibition of uptake of [3H]monoamines into synaptosomes from different regions of rat brain

Entactogens: How the Name for a Novel Class of Psychoactive Agents Originated

At first glance, it appears there is little difference between the molecular structures of methylenedioxymethamphetamine (MDMA), which has an N-methyl attached to its amino group, and methylenedioxyamphetamine (MDA), a primary amine that is recognized to have hallucinogenic activity. It is known from studies with other hallucinogenic amphetamines that N-methylation of hallucinogenic amphetamines attenuates or abolishes hallucinogenic activity. Nevertheless, MDMA is biologically active and has a potency only slightly less than its MDA parent. Importantly, it is the Ievo-isomer of hallucinogenic phenethylamines that is more biologically active, whereas it is the dextro isomer of MDMA that is more active. This reversal of stereochemistry for the activity of two very closely related molecules is a very powerful clue that their mechanisms of action differ. Finally, extension of the alpha-methyl of hallucinogenic amphetamines to an alpha-ethyl moiety completely abolishes their hallucinogenic activity. Ultimately, we extended the alpha-methyl group of MDMA to an alpha-ethyl to afford a molecule we named (N-Methyl-1-(1,3-benzodioxol-5-yl)-2-butanamine (MBDB) that retained significant MDMA-like psychoactivity. Hence, there are three structural features that distinguish MDMA from the hallucinogenic amphetamines: (1) the N-methyl on the basic nitrogen, (2) the reversal of stereochemistry and, (3) tolerance of an alpha-ethyl moiety as contrasted with the alpha-methyl of hallucinogenic phenethylamines. Clearly, MDMA is distinct from classical hallucinogenic phenethylamines in its structure, and its psychopharmacology is also unique. Thus, in 1986 I proposed the name "Entactogen" for the pharmacological class of drugs that includes 3,4-methylenedioxymethamphetamine (MDMA) and other substances with a similar psychopharmacological effect. The name is derived from roots that indicate that entactogens produce a "touching within." Rather than having significant psychostimulant, or hallucinogenic effects, MDMA powerfully promotes affiliative social behavior, has acute anxiolytic effects, and can lead to profound states of introspection and personal reflection. Its mechanism of action is now established as involving transport of MDMA by the neuronal serotonin reuptake carrier followed by carrier-mediated release of stored neuronal serotonin.

Extinction training following cocaine or MDMA self-administration produces discrete changes in D2-like and mGlu5 receptor density in the rat brain

BACKGROUND

Several studies strongly support the role of the dopamine D2-like and glutamate mGlu5 receptors in psychostimulant reward and relapse.

METHODS

The present study employed cocaine or MDMA self-administration with yoked-triad procedure in rats to explore whether extinction training affects the drug-seeking behavior and the D2-like and mGlu5 receptor Bmax and Kd values in several regions of the animal brain.

RESULTS

Both cocaine and MDMA rats developed maintenance of self-administration, but MDMA evoked lower response rates and speed of self-administration acquisition. During reinstatement tests, cocaine or MDMA seeking behavior was produced by either exposure to the drug-associated cues or drug-priming injections. The extinction training after cocaine self-administration did not alter significantly D2-like receptor expression the in the limbic and subcortical brain areas, while MDMA yoked rats showed a decrease of the D2-like binding density in the nucleus accumbens and increase in the hippocampus and a rise of affinity in the striatum and hippocampus. Interestingly, in the prefrontal cortex a reduction in the mGlu5 receptor density in cocaine- or MDMA-abstinent rats was demonstrated, with significant effects being observed after previous MDMA exposure. Moreover, rats self-administered cocaine showed a rise in the density of mGlu5 receptor for the nucleus accumbens.

CONCLUSION

This study first time shows that abstinence followed extinction training after cocaine or MDMA self- or passive-injections changes the D2-like and mGlu5 density and affinity. The observed changes in the expression of both receptors are brain-region specific and related to either pharmacological and/or motivational features of cocaine or MDMA.

Reduced Efficacy of d-Amphetamine and 3,4-Methylenedioxymethamphetamine in Inducing Hyperactivity in Mice Lacking the Postsynaptic Scaffolding Protein SHANK1

Genetic defects in the three SH3 and multiple ankyrin repeat domains (SHANK) genes (SHANK1, SHANK2, and SHANK3) are associated with multiple major neuropsychiatric disorders, including autism spectrum disorder (ASD), schizophrenia (SCZ), and bipolar disorder (BPD). Psychostimulant-induced hyperactivity is a commonly applied paradigm to assess behavioral phenotypes related to BPD and considered to be the gold standard for modeling mania-like elevated drive in mouse models. Therefore, the goal of our present study was to test whether Shank1 plays a role in the behavioral effects of psychostimulants and whether this is associated with genotype-dependent neurochemical alterations. To this aim, male and female null mutant Shank1^-/- mice were treated with d-amphetamine (AMPH; 2.5 mg/kg) and 3,4-methylenedioxymethamphetamine (MDMA, commonly known as ecstasy; 20 mg/kg), and psychostimulant-induced hyperactivity was compared to heterozygous Shank1^+/- and wildtype Shank1^+/+ littermate controls. Results show that Shank1^-/- mice display reduced psychostimulant-induced hyperactivity, although psychostimulants robustly stimulated locomotor activity in littermate controls. Shank1 deletion effects emerged throughout development, were particularly prominent in adulthood, and seen in response to both psychostimulants, i.e., AMPH and MDMA. Specifically, while AMPH-induced hyperactivity was reduced but still detectable in Shank1^-/- mice, MDMA-induced hyperactivity was robustly blocked and completely absent in Shank1^-/- mice. Reduced efficacy of psychostimulants to stimulate hyperactivity in Shank1^-/- mice might be associated with alterations in the neurochemical architecture in prefrontal cortex, nucleus accumbens, and hypothalamus. Our observation that psychostimulant-induced hyperactivity is reduced rather than enhanced in Shank1^-/- mice clearly speaks against a behavioral phenotype with relevance to BPD. Lack of BPD-like phenotype is consistent with currently available human data linking mutations in SHANK2 and SHANK3 but not SHANK1 to BPD.

Dark Classics in Chemical Neuroscience: 3,4-Methylenedioxymethamphetamine

Better known as "ecstasy", 3,4-methylenedioxymethamphetamine (MDMA) is a small molecule that has played a prominent role in defining the ethos of today's teenagers and young adults, much like lysergic acid diethylamide (LSD) did in the 1960s. Though MDMA possesses structural similarities to compounds like amphetamine and mescaline, it produces subjective effects that are unlike any of the classical psychostimulants or hallucinogens and is one of the few compounds capable of reliably producing prosocial behavioral states. As a result, MDMA has captured the attention of recreational users, the media, artists, psychiatrists, and neuropharmacologists alike. Here, we detail the synthesis of MDMA as well as its pharmacology, metabolism, adverse effects, and potential use in medicine. Finally, we discuss its history and why it is perhaps the most important compound for the future of psychedelic science-having the potential to either facilitate new psychedelic research initiatives, or to usher in a second Dark Age for the field.

Acute effects of 3,4-methylenedioxymethamphetamine (MDMA) and R(-) MDMA on actigraphy-based daytime activity and sleep parameters in rhesus monkeys

3,4-Methylenedioxymethamphetamine (MDMA) affects monoaminergic pathways that play a critical role in sleep-wake cycles. Dopaminergic mechanisms are thought to mediate the sleep-disrupting effects of stimulant drugs. However, the mechanisms underlying the effects of MDMA on sleep-wake cycles and the effects of R(-) MDMA, a stereoisomer that lacks dopaminergic activity, on sleep remain unknown. The aim of the present study was to investigate the effects of racemic MDMA and R(-) MDMA on daytime activity and sleep-like parameters evaluated with actigraphy in adult rhesus macaques (Macaca mulatta, n = 6). Actiwatch monitors were attached to the monkeys' collars and actigraphy recording was conducted during baseline conditions and after the administration of acute intramuscular injections of saline (vehicle), racemic MDMA (0.3, 1.0, or 1.7 mg/kg), or R(-) MDMA (0.3, 1.0, or 1.7 mg/kg) at 9 or 16 h (3 h before "lights off"). Morning treatments had no effects on sleep-like parameters. Racemic MDMA decreased general daytime activity during the first hour after injection and increased daytime activity at 3 hr posttreatment. Although afternoon administration of racemic MDMA increased sleep latency, it improved other sleep parameters, decreasing wake time after sleep onset (WASO) and increasing sleep efficiency for subjects with low baseline sleep efficiency. Afternoon treatment with R(-) MDMA improved sleep measures, increasing sleep efficiency and decreasing sleep latency and WASO, while having no effects on daytime activity. The stimulant and sleep-disrupting effects of racemic MDMA are likely mediated by dopaminergic and noradrenergic mechanisms, while serotonergic pathways appear to be involved in the sleep-promoting effects of MDMA. (PsycINFO Database Record

(±)-MDMA and its enantiomers: potential therapeutic advantages of R(-)-MDMA

The use of (±)-3,4-methylenedioxymethamphetamine ((±)-MDMA) as an adjunct to psychotherapy in the treatment of psychiatric and behavioral disorders dates back over 50 years. Only in recent years have controlled and peer-reviewed preclinical and clinical studies lent support to (±)-MDMA's hypothesized clinical utility. However, the clinical utility of (±)-MDMA is potentially mitigated by a range of demonstrated adverse effects. One potential solution could lie in the individual S(+) and R(-) enantiomers that comprise (±)-MDMA. Individual enantiomers of racemic compounds have been employed in psychiatry to improve a drug's therapeutic index. Although no research has explored the individual effects of either S(+)-MDMA or R(-)-MDMA in humans in a controlled manner, preclinical research has examined similarities and differences between the two molecules and the racemic compound. This review addresses information related to the pharmacodynamics, neurotoxicity, physiological effects, and behavioral effects of S(+)-MDMA and R(-)-MDMA that might guide preclinical and clinical research. The current preclinical evidence suggests that R(-)-MDMA may provide an improved therapeutic index, maintaining the therapeutic effects of (±)-MDMA with a reduced side effect profile, and that future investigations should investigate the therapeutic potential of R(-)-MDMA.

Non-Serotonergic Neurotoxicity by MDMA (Ecstasy) in Neurons Derived from Mouse P19 Embryonal Carcinoma Cells

3,4-methylenedioxymethamphetamine (MDMA; ecstasy) is a commonly abused recreational drug that causes neurotoxic effects in both humans and animals. The mechanism behind MDMA-induced neurotoxicity is suggested to be species-dependent and needs to be further investigated on the cellular level. In this study, the effects of MDMA in neuronally differentiated P19 mouse embryonal carcinoma cells have been examined. MDMA produces a concentration-, time- and temperature-dependent toxicity in differentiated P19 neurons, as measured by intracellular MTT reduction and extracellular LDH activity assays. The P19-derived neurons express both the serotonin reuptake transporter (SERT), that is functionally active, and the serotonin metabolizing enzyme monoamine oxidase A (MAO-A). The involvement of these proteins in the MDMA-induced toxicity was investigated by a pharmacological approach. The MAO inhibitors clorgyline and deprenyl, and the SERT inhibitor fluoxetine, per se or in combination, were not able to mimic the toxic effects of MDMA in the P19-derived neurons or block the MDMA-induced cell toxicity. Oxidative stress has been implicated in MDMA-induced neurotoxicity, but pre-treatment with the antioxidants α-tocopherol or N-acetylcysteine did not reveal any protective effects in the P19 neurons. Involvement of mitochondria in the MDMA-induced cytotoxicity was also examined, but MDMA did not alter the mitochondrial membrane potential (ΔΨm) in the P19 neurons. We conclude that MDMA produce a concentration-, time- and temperature-dependent neurotoxicity and our results suggest that the mechanism behind MDMA-induced toxicity in mouse-derived neurons do not involve the serotonergic system, oxidative stress or mitochondrial dysfunction.

Evaluation of brain SERT occupancy by resveratrol against MDMA-induced neurobiological and behavioral changes in rats: A 4-[¹⁸F]-ADAM/small-animal PET study

The misuse of 3,4-methylenedioxymethamphetamine (MDMA) has drawn a growing concern worldwide for its psychophysiological impacts on humans. MDMA abusers are often accompanied by long-term serotonergic neurotoxicity, which is associated with reduced density of cerebral serotonin transporters (SERT) and depressive disorders. Resveratrol (RSV) is a natural polyphenolic phytoalexin that has been known for its antidepressant and neuroprotective effects. However, biological targets of RSV as well as its neuroprotective effects against MDMA remained largely unknown. In this study, we examined binding potency of RSV and MDMA to SERT using small-animal positron emission tomography (PET) with the SERT radioligand, N,N-dimethyl-2-(2-amino-4-[(18)F]fluorophenylthio)benzylamine (4-[(18)F]-ADAM) and investigated the protection of RSV against the acute and long-term adverse effects of MDMA. We found that RSV exhibit binding potentials to SERT in vivo in a dose-dependent manner with variation among brain regions. When the MDMA-treated rats (10mg/kg, s.c.) were co-injected with RSV (20mg/kg, i.p.) twice daily for 4 consecutive days, MDMA-induced acute elevation in plasma corticosterone was significantly reduced. Further, 4-[(18)F]-ADAM PET imaging revealed that RSV protected against the MDMA-induced decrease in SERT availability in the midbrain and the thalamus 2 weeks following the co-treatment. The PET data were comparable to the observation from the forced swim test that RSV sufficiently ameliorated the depressive-like behaviors of the MDMA-treated rats. Together, these findings suggest that RSV is a potential antidepressant and may confer protection against neurobiological and behavioral changes induced by MDMA.

Constructing the ecstasy of MDMA from its component mental organs: Proposing the primer/probe method

The drug MDMA, commonly known as ecstasy, produces a specific and distinct open hearted mental state, which led to the creation of a new pharmacological class, "entactogens". Extensive literature on its mechanisms of action has come to characterize MDMA as a "messy" drug with multiple mechanisms, but the consensus is that the distinctive entactogenic effects arise from the release of neurotransmitters, primarily serotonin. I propose an alternative hypothesis: The entactogenic mental state is due to the simultaneous direct activation of imidazoline-1 (I1) and serotonin-2 (5-HT2) receptors by MDMA. This hypothesis emerges from "mental organ" theory, which embodies many hypotheses, the most relevant of which are: "Mental organs" are populations of neurons that all express their defining metabotropic receptor, and each mental organ plays a distinct role in the mind, a role shaped by evolution as mental organs evolve by duplication and divergence. Mental organs are the mechanism by which evolution sculpts the mind. Mental organs can be in or out of consciousness. In order for a mental organ to enter consciousness, three things must happen: The mental organ must be activated directly at its defining receptor. 5-HT2 must be simultaneously activated. One of the functions of activated 5-HT2 is to load other simultaneously activated mental organs fully into consciousness. In some cases THC must be introduced to remove long-term blocks mediated by the cannabinoid system. I propose the "primer/probe" method to test these hypotheses. A "primer" is a drug that selectively activates 5-HT2 (e.g. DOB or MEM) or serotonin-1 (5-HT1) and 5-HT2 (e.g. DOET or 2C-B-fly). A "probe" is a drug that activates a receptor whose corresponding mental organ we wish to load into consciousness in order to understand its role in the mind. The mental organ is loaded into consciousness when the primer and probe are taken together, but not when taken separately. For example, the blood pressure medications rilmenidine and moxonidine are selective for imidazoline-1 and can be used to test the hypothesis that the entactogenic mental effects of MDMA are due to loading the imidazoline-1 mental organ into consciousness. The primer/probe method is not limited to testing the specific hypothesis about MDMA and imidazoline, but is a general method for studying the role of mental organs in the mind. For example, the role of dopamine mental organs can be studied by using Parkinson's drugs such as ropinirole or pramipexole as probes.

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.

MDMA for the treatment of mood disorder: all talk no substance?

BACKGROUND

Unipolar depression is the third highest contributor to the global burden of disease, yet current pharmacotherapies typically take about 6 weeks to have an effect. A rapid-onset agent is an attractive prospect, not only to alleviate symptoms before first-line antidepressants display therapeutic action, but as a further treatment option in nonresponsive cases. It has been suggested that 3,4-methylene-dioxymethamphetamine (MDMA) could play a part in the treatment of depression, either as a rapid-onset pharmacological agent or as an adjunct to psychotherapy. Whilst these hypotheses are in keeping with the monoamine theory of depression and the principles surrounding psychotherapy, explicit experimental evidence of an antidepressant effect of MDMA has rarely been established.

AIMS

To address the hypothesis surrounding MDMA as a rapid-onset antidepressant by examining pharmacological, psychological and behavioural studies. We consider whether this therapy could be safe by looking at the translation of neurotoxicity data from animals to humans.

METHOD

A literature review of the evidence supporting this hypothesis was performed.

CONCLUSIONS

The pharmacology of MDMA offers a promising target as a rapid-onset agent and MDMA is currently being investigated for use in psychotherapy in anxiety disorders; translation from these studies for use in depression may be possible. However, experimental evidence and safety analysis are insufficient to confirm or reject this theory at present.

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.

5-hydroxytryptamine- and dopamine-releasing effects of ring-substituted amphetamines on rat brain: a comparative study using in vivo microdialysis

Using in vivo microdialysis, a comparative study was conducted to examine the effects of amphetamine-related compounds (methamphetamine, MAP; 3,4-methylenedioxymethamphetamine, MDMA; p-methoxyamphetamine, PMA; p-methoxymethamphetamine, PMMA; 4-methylthioamphetamine, 4-MTA; 3,4,5-trimethoxyamphetamine, TMA; 2,5-dimethoxy-4-iodoamphetamine, DOI) on extracellular levels of serotonin (5-HT) and dopamine (DA). Dialysates were assayed using HPLC equipped with electrochemical detector following i.p. administration with each drug at a dose of 5 mg/kg. MAP was found to drastically and rapidly increase 5-HT and DA levels (870% and 1460%, respectively). PMA, PMMA, and 4-MTA slightly increased DA levels (150-290%) but remarkably increased 5-HT levels (540-900%). In contrast, TMA and DOI caused no detectable changes in levels of both monoamines. We observed that the potent DA-releasing action of MAP was remarkably decreased by introduction of methoxy or methylthio group at the para position (MAP vs. PMMA or 4-MTA), but introduction of two additional adjacent methoxy groups into PMA totally abolished its 5-HT-/DA-releasing action (PMA vs. TMA). In addition, para-mono-substituted compounds inhibited both monoamine oxidase (MAO) enzymes more strongly than other compounds; PMA and 4-MTA exhibited submicromolar IC50 values for MAO-A. On the other hand, TMA scarcely affected the activity of both MAO enzymes as well as extracellular levels of 5-HT and DA. In this comparative study, MDMA, PMA, and 4-MTA functioned similar to PMMA, a typical empathogen; these findings therefore could be helpful in clarifying the psychopharmacological properties of amphetamine-related, empathogenic designer drugs.

Mephedrone: Public health risk, mechanisms of action, and behavioral effects

The recent shortage of 3,4-methylenedioxymethamphetamine (MDMA, Ecstasy) has led to an increased demand for alternative amphetamine-like drugs such as the synthetic cathinone, 4-methylmethcathinone (mephedrone). Despite the re-classification of mephedrone as a Class B restricted substance by the United Kingdom and restrictive legislation by the United States, international policy regarding mephedrone control is still developing and interest in synthetic amphetamine-like drugs could drive the development of future mephedrone analogues. Currently, there is little literature investigating the mechanism of action and long-term effects of mephedrone. As such, we reviewed the current understanding of amphetamines, cathinones, and cocaine emphasizing the potentially translational aspects to mephedrone, as well as contrasting with the work that has been done specifically on mephedrone in order to present the current state of understanding of mephedrone in terms of its risks, mechanisms, and behavioral effects. Emerging research suggests that while there are structural and behavioral similarities of mephedrone with amphetamine-like compounds, it appears that serotonergic signaling may mediate more of mephedrone's effects unlike the more dopaminergic dependent effects observed in traditional amphetamine-like compounds. As new designer drugs are produced, current and continuing research on mephedrone and other synthetic cathinones should help inform policymakers' decisions regarding the regulation of novel 'legal highs.'

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.

Pharmacological characterization of designer cathinones in vitro

BACKGROUND AND PURPOSE

Designer β-keto amphetamines (e.g. cathinones, 'bath salts' and 'research chemicals') have become popular recreational drugs, but their pharmacology is poorly characterized.

EXPERIMENTAL APPROACH

We determined the potencies of cathinones to inhibit DA, NA and 5-HT transport into transporter-transfected HEK 293 cells, DA and 5-HT efflux from monoamine-preloaded cells, and monoamine receptor binding affinity.

KEY RESULTS

Mephedrone, methylone, ethylone, butylone and naphyrone acted as non-selective monoamine uptake inhibitors, similar to cocaine. Mephedrone, methylone, ethylone and butylone also induced the release of 5-HT, similar to 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) and other entactogens. Cathinone, methcathinone and flephedrone, similar to amphetamine and methamphetamine, acted as preferential DA and NA uptake inhibitors and induced the release of DA. Pyrovalerone and 3,4-methylenedioxypyrovalerone (MDPV) were highly potent and selective DA and NA transporter inhibitors but unlike amphetamines did not evoke the release of monoamines. The non-β-keto amphetamines are trace amine-associated receptor 1 ligands, whereas the cathinones are not. All the cathinones showed high blood-brain barrier permeability in an in vitro model; mephedrone and MDPV exhibited particularly high permeability.

CONCLUSIONS AND IMPLICATIONS

Cathinones have considerable pharmacological differences that form the basis of their suggested classification into three groups. The predominant action of all cathinones on the DA transporter is probably associated with a considerable risk of addiction.

Implications of central immune signaling caused by drugs of abuse: mechanisms, mediators and new therapeutic approaches for prediction and treatment of drug dependence

In the past two decades a trickle of manuscripts examining the non-neuronal central nervous system immune consequences of the drugs of abuse has now swollen to a significant body of work. Initially, these studies reported associative evidence of central nervous system proinflammation resulting from exposure to the drugs of abuse demonstrating key implications for neurotoxicity and disease progression associated with, for example, HIV infection. However, more recently this drug-induced activation of central immune signaling is now understood to contribute substantially to the pharmacodynamic actions of the drugs of abuse, by enhancing the engagement of classical mesolimbic dopamine reward pathways and withdrawal centers. This review will highlight the key in vivo animal, human, biological and molecular evidence of these central immune signaling actions of opioids, alcohol, cocaine, methamphetamine, and 3,4-methylenedioxymethamphetamine (MDMA). Excitingly, this new appreciation of central immune signaling activity of drugs of abuse provides novel therapeutic interventions and opportunities to identify 'at risk' individuals through the use of immunogenetics. Discussion will also cover the evidence of modulation of this signaling by existing clinical and pre-clinical drug candidates, and novel pharmacological targets. Finally, following examination of the breadth of central immune signaling actions of the drugs of abuse highlighted here, the current known common immune signaling components will be outlined and their impact on established addiction neurocircuitry discussed, thereby synthesizing a common neuroimmune hypothesis of addiction.

From Bench to Bedside: Understanding the Science behind the Pharmacologic Management of MDMA- and other Sympathomimetic-Mediated Hyperthermia

Objective:

To evaluate the scientific rationale and efficacy of pharmacologic and nonpharmacologic treatments for sympathomimetic-induced hyperthermia and related sequelae.

Data Sources:

Literature was accessed through MEDLINE (1940-September 2010) using the terms MDMA [3,4-methylenedioxymethamphetamine], methamphetamine, toxicity, and hyperthermia. In addition, reference citations from identified publications were reviewed.

Study Selection and Data Extraction:

All articles written in English identified from data sources were evaluated.

Data Synthesis:

The treatment of sympathomimetic-induced hyperthermia is a challenging problem for health-care professionals. The lack of clinical trials further complicates the development of evidence-based treatment algorithms. Preclinical studies have mostly been with the sympathomimetic MDMA and have demonstrated a reversal of MDMA-induced hyperthermia with a mixed serotonin 5-HT1A agonist/5-HT2A antagonist or mixed α1- and β1,2,3-adrenergic receptor antagonists.

Conclusions:

Because of the nature by which patients are exposed to these agents, therapeutic interventions for sympathomimetic-mediated hyperthermia still lack evidence from clinical trials with human subjects. Pharmacologic treatments that should be avoided are antipyretics and the ryanodine receptor antagonist dantrolene. Promising future therapies may involve mixed 5-HT1A agonist/5-HT2A antagonists such as the atypical antipsychotic olanzapine, or mixed α1- and β1,2,3-adrenergic receptor antagonists such as carvedilol, as current preclinical research suggests.

Differential effects of cocaine and MDMA self-administration on cortical serotonin transporter availability in monkeys

Cocaine self-administration alters brain dopaminergic and serotonergic function primarily in mesolimbic and prefrontal brain regions whereas 3,4-methylenedioxymethamphetamine (MDMA) self-administration predominately alters brain serotonergic function in a more widespread distribution across cortical regions. We previously reported that, compared to drug-naïve rhesus monkeys, self-administration of cocaine but not MDMA was associated with increased serotonin transporter (SERT) availability in two mesolimbic regions, the caudate nucleus and putamen, as measured by positron emission tomography (PET) using the SERT-specific ligand [(11)C]-3-amino-4(2-dimethylamino-methyl-phenylsulfanyl)-benzonitrile ([(11)C]DASB). The goal of the present study was to extend this comparison between cocaine and MDMA self-administration to SERT availability in cortical regions, which have been shown previously to be affected in human drug abusers and are associated with executive function. PET studies using [(11)C]DASB were conducted in adult male rhesus monkeys with a history of cocaine (mean intake = 742.6 mg/kg) or MDMA (mean intake = 121.0 mg/kg) self-administration, and drug-naïve controls (n = 4/group). Regions of interest were drawn for several cortical (prefrontal, temporal, parietal, occipital and midcingulate) and subcortical (thalamus, amygdala and hippocampus) areas. Cortical SERT availability was significantly higher in monkeys with a cocaine self-administration history compared to controls whereas MDMA self-administration resulted in lower levels of SERT availability. These data extend our previous findings indicating that cocaine and MDMA self-administration differentially alter SERT availability in subcortical and cortical regions, which may have implications for development of treatment drugs.

Contributions of serotonin in addiction vulnerability

The serotonin (5-hydroxytryptamine; 5-HT) system has long been associated with mood and its dysregulation implicated in the pathophysiology of mood and anxiety disorders. While modulation of 5-HT neurotransmission by drugs of abuse is also recognized, its role in drug addiction and vulnerability to drug relapse is a more recent focus of investigation. First, we review preclinical data supporting the serotonergic raphe nuclei and their forebrain projections as targets of drugs of abuse, with emphasis on the effects of psychostimulants, opioids and ethanol. Next, we examine the role of 5-HT receptors in impulsivity, a core behavior that contributes to the vulnerability to addiction and relapse. Finally, we discuss evidence for serotonergic dysregulation in comorbid mood and addictive disorders and suggest novel serotonergic targets for the treatment of addiction and the prevention of drug relapse.

A role for adenosine A(1) receptor blockade in the ability of caffeine to promote MDMA "Ecstasy"-induced striatal dopamine release

Co-administration of caffeine profoundly enhances the acute toxicity of 3,4 methylenedioxymethamphetamine (MDMA) in rats. The aim of this study was to determine the ability of caffeine to impact upon MDMA-induced dopamine release in superfused brain tissue slices as a contributing factor to this drug interaction. MDMA (100 and 300μM) induced a dose-dependent increase in dopamine release in striatal and hypothalamic tissue slices preloaded with [(3)H] dopamine (1μM). Caffeine (100μM) also induced dopamine release in the striatum and hypothalamus, albeit to a much lesser extent than MDMA. When striatal tissue slices were superfused with MDMA (30μM) in combination with caffeine (30μM), caffeine enhanced MDMA-induced dopamine release, provoking a greater response than that obtained following either caffeine or MDMA applications alone. The synergistic effects in the striatum were not observed in hypothalamic slices. As adenosine A(1) receptors are, one of the main pharmacological targets of caffeine, which are known to play an important role in the regulation of dopamine release, their role in the modulation of MDMA-induced dopamine release was investigated. 1μM 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), a specific A(1) antagonist, like caffeine, enhanced MDMA-induced dopamine release from striatal slices while 1μM 2,chloro-N(6)-cyclopentyladenosine (CCPA), a selective adenosine A(1) receptor agonist, attenuated this. Treatment with either SCH 58261, a selective A(2A) receptor antagonist, or rolipram, a selective PDE-4 inhibitor, failed to reproduce a caffeine-like effect on MDMA-induced dopamine release. These results suggest that caffeine regulates MDMA-induced dopamine release in striatal tissue slices, via inhibition of adenosine A(1) receptors.

Reinstatement of extinguished amphetamine self-administration by 3,4-methylenedioxymethamphetamine (MDMA) and its enantiomers in rhesus monkeys

RATIONALE

The effectiveness of MDMA and its enantiomers to reinstate responding previously maintained by drug self-administration has not been thoroughly investigated.

OBJECTIVES

The present study was designed to compare the reinstatement effects of amphetamine, the piperazine-analog BZP, SR(+/-)-MDMA, S(+)-MDMA, R(-)-MDMA, and fenfluramine on behavior maintained under a second-order schedule of intravenous amphetamine self-administration in rhesus monkeys (n=4).

METHODS

Following saline substitution and extinction, a range of doses of amphetamine, BZP, SR(+/-)-MDMA, S(+)-MDMA, R(-)-MDMA, and fenfluramine were administered i.v. as non-contingent priming injections in order to characterize their effectiveness to reinstate responding previously maintained by amphetamine self-administration.

RESULTS

Priming injections of amphetamine, BZP, SR(+/-)-MDMA, and S(+)-MDMA induced significant reinstatement effects. In contrast, neither R(-)-MDMA nor fenfluramine effectively reinstated behavior. Pretreatment with the selective serotonin transporter inhibitor, fluoxetine, attenuated the reinstatement effects of SR(+/-)-MDMA, S(+)-MDMA, and BZP but had no significant effect on amphetamine-primed reinstatement.

CONCLUSIONS

Given the profile of neurochemical effects published previously, these findings suggest that the reinstatement effects of MDMA are mediated primarily by dopamine release; however, the attenuation of MDMA-induced reinstatement by fluoxetine supports previous research demonstrating the complex behavioral pharmacology of MDMA-like drugs and that the reinstatement effects of MDMA are at least partially mediated by serotonergic mechanisms.

Pharmacological aspects of the combined use of 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) and gamma-hydroxybutyric acid (GHB): a review of the literature

Epidemiological studies show that the use of club drugs is on the rise. Furthermore, the last few decades have seen a rise in patterns of polydrug use. One of the combinations frequently used is ecstasy (MDMA) with gammahydroxybutyrate (GHB). For effective prevention it is important to be aware of this phenomenon and of the pharmacology of these drugs. The effects of the combination extend to different neurotransmitter systems, including serotonin, dopamine and noradrenaline. Studies investigating the effects of combinations of psychoactive substances are limited. In this review we describe the subjective effects of the MDMA/GHB combination. Furthermore, we review the individual actions of MDMA on serotonin, dopamine and noradrenaline systems. In addition, actions of GHB on these systems are discussed as a possible pharmacological basis for the interaction of both drugs. It is postulated that GHB attenuates the unpleasant or dysphoric effects of MDMA by its effect on the central dopaminergic system.

MDMA induces EPSP-Spike potentiation in rat ventral hippocampus in vitro via serotonin and noradrenaline release and coactivation of 5-HT4 and beta1 receptors

It is well documented that N-methyl-3,4-methylenedioxyamphetamine (MDMA, ecstasy) releases brain serotonin (5-HT; 5-hydroxytryptamine), noradrenaline (NE; norepinephrine), and dopamine, but the consequent effect on brain functioning remains elusive. In this study, we characterized the effects of MDMA on electrically evoked responses in the ventral CA1 region of a rat hippocampal slice preparation. Superfusion with MDMA (10 microM, 30 min) increased the population spike amplitude (PSA) by 48.9+/-31.2% and decreased population spike latency (PSL) by 103+/-139 mus (both: mean+/-SD, n=123; p<0.0001, Wilcoxon test), without affecting field excitatory postsynaptic potential (fEPSP). This effect persisted for at least 1 h after MDMA washout; we have called this EPSP-spike potentiation (ESP) by MDMA, ESP MDMA. Antagonism of GABAergic transmission did not prevent ESP MDMA, suggesting that an increase in excitability of pyramidal cells underlies this MDMA action. Block of serotonin transporter (SERT) with citalopram or 5-HT depletion with (+/-)-p-chlorophenylalanine pretreatment partially inhibited the ESP MDMA. Block of both SERT and NE transporter prevented ESP MDMA, indicating its dependence on release of both 5-HT and NE. ESP MDMA is produced by simultaneous activation of 5-HT4 and beta1 receptors, with a predominant role of 5-HT4 receptors. Block of both 5-HT4 and beta1 receptors revealed an inhibitory component of the MDMA action mediated by 5-HT1A receptor. The concentration range of MDMA which produced ESP MDMA (1-30 microM) corresponds to that commonly reached in human plasma following the ingestion of psychoactive MDMA doses, suggesting that release of both 5-HT and NE, and consequent ESP MDMA may underlie some of the psychoactive effects of MDMA in humans.

Effects of cocaine and MDMA self-administration on serotonin transporter availability in monkeys

Although serotonin (5-HT) can interact with dopamine (DA) systems to modulate the subjective and reinforcing effects of psychostimulants such as cocaine and 3,4-methyldioxymethamphetamine (MDMA, ecstasy), the long-term effects of exposure to psychostimulants on brain 5-HT systems are not well characterized. The present study assessed 5-HT transporter (SERT) availability using positron emission tomography (PET) in rhesus monkeys with the SERT-specific radioligand [(11)C]3-amino-4-(2-dimethylaminomethyl-phenylsulfanyl)-benzonitrile (DASB). SERT availability was assessed in regions of interest including the caudate nucleus, putamen, anterior cingulate cortex, and cerebellum. [(11)C]DASB distribution volume ratios (DVRs) were calculated using the cerebellum as the reference region. DVRs were calculated in control monkeys and in cocaine or MDMA self-administering monkeys approximately 24 h after the last self-administration (SA) session. SERT availability did not differ between monkeys with a history of MDMA SA and control monkeys in any region examined. In contrast, monkeys with a history of cocaine SA showed significantly higher levels of SERT availability in the caudate nucleus and putamen compared to control subjects. These results suggest that chronic SA of cocaine, but not MDMA, leads to alterations in serotonergic function in brain areas relevant to drug abuse. The higher level of SERT availability in cocaine-experienced monkeys may lead to a reduced inhibitory tone of 5-HT on the DA system, which may explain, in part, differences in the abuse liability between cocaine and MDMA.

The recreational drug ecstasy disrupts the hypothalamic-pituitary-gonadal reproductive axis in adult male rats

Reproductive function involves an interaction of three regulatory levels: hypothalamus, pituitary, and gonad. The primary drive upon this system comes from hypothalamic gonadotropin-releasing hormone (GnRH) neurosecretory cells, which receive afferent inputs from other neurotransmitter systems in the central nervous system to result in the proper coordination of reproduction and the environment. Here, we hypothesized that the recreational drug (+/-)-3,4-methylenedioxymethamphetamine (MDMA; 'ecstasy'), which acts through several of the neurotransmitter systems that affect GnRH neurons, suppresses the hypothalamic-pituitary-gonadal reproductive axis of male rats. Adult male Sprague-Dawley rats self-administered saline or MDMA either once (acute) or for 20 days (chronic) and were euthanized 7 days following the last administration. We quantified hypothalamic GnRH mRNA, serum luteinizing hormone concentrations, and serum testosterone levels as indices of hypothalamic, pituitary, and gonadal functions, respectively. The results indicate that the hypothalamic and gonadal levels of the hypothalamic-pituitary-gonadal axis are significantly altered by MDMA, with GnRH mRNA and serum testosterone levels suppressed in rats administered MDMA compared to saline. Furthermore, our finding that hypothalamic GnRH mRNA levels are suppressed in the context of low testosterone concentrations suggests that the central GnRH neurosecretory system may be a primary target of inhibitory regulation by MDMA usage.

Actions of 3,4-methylenedioxymethamphetamine (MDMA) on cerebral dopaminergic, serotonergic and cholinergic neurons

3,4-Methylenedioxymethamphetamine (MDMA) is an amphetamine derivative and a popular drug of abuse that exhibits mild hallucinogenic and rewarding properties and engenders feelings of connectedness and openness. The unique psychopharmacological profile of this drug of abuse most likely is derived from the property of MDMA to promote the release of dopamine and serotonin (5-HT) in multiple brain regions. The present review highlights primarily data from studies employing in vivo microdialysis that detail the actions of MDMA on the release of these neurotransmitters. Data from in vivo microdialysis experiments indicate that MDMA, like most amphetamine derivatives, increases the release of dopamine in the striatum, n. accumbens and prefrontal cortex. However, the release of dopamine evoked by MDMA in each of these brain regions appears to be modulated by concomitantly released 5-HT and the subsequent activation of 5-HT2A/C or 5-HT2B/C receptors. In addition to its stimulatory effect on the release of monoamines, MDMA also enhances the release of acetylcholine in the striatum, hippocampus and prefrontal cortex, and this cholinergic response appears to be secondary to the activation of histaminergic, dopaminergic and/or serotonergic receptors. Beyond the acute stimulatory effect of MDMA on neurotransmitter release, MDMA also increases the extracellular concentration of energy substrates, e.g., glucose and lactate in the brain. In contrast to the acute stimulatory actions of MDMA on the release of monoamines and acetylcholine, the repeated administration of high doses of MDMA is thought to result in a selective neurotoxicity to 5-HT axon terminals in the rat. Additional studies are reviewed that focus on the alterations in neurotransmitter responses to pharmacological and physiological stimuli that accompany MDMA-induced 5-HT neurotoxicity.

Comparative potencies of 3,4-methylenedioxymethamphetamine (MDMA) analogues as inhibitors of [3H]noradrenaline and [3H]5-HT transport in mammalian cell lines

BACKGROUND AND PURPOSE

Illegal 'ecstasy' tablets frequently contain 3,4-methylenedioxymethamphetamine (MDMA)-like compounds of unknown pharmacological activity. Since monoamine transporters are one of the primary targets of MDMA action in the brain, a number of MDMA analogues have been tested for their ability to inhibit [3H]noradrenaline uptake into rat PC12 cells expressing the noradrenaline transporter (NET) and [3H]5-HT uptake into HEK293 cells stably transfected with the 5-HT transporter (SERT).

EXPERIMENTAL APPROACH

Concentration-response curves for the following compounds at both NET and SERT were determined under saturating substrate conditions: 4-hydroxy-3-methoxyamphetamine (HMA), 4-hydroxy-3-methoxymethamphetamine (HMMA), 3,4-methylenedioxy-N-hydroxyamphetamine (MDOH), 2,5-dimethoxy-4-bromophenylethylamine (2CB), 3,4-dimethoxymethamphetamine (DMMA), 3,4-methylenedioxyphenyl-2-butanamine (BDB), 3,4-methylenedioxyphenyl-N-methyl-2-butanamine (MBDB) and 2,3-methylenedioxymethamphetamine (2,3-MDMA).

KEY RESULTS

2,3-MDMA was significantly less potent than MDMA at SERT, but equipotent with MDMA at NET. 2CB and BDB were both significantly less potent than MDMA at NET, but equipotent with MDMA at SERT. MBDB, DMMA, MDOH and the MDMA metabolites HMA and HMMA, were all significantly less potent than MDMA at both NET and SERT.

CONCLUSIONS AND IMPLICATIONS

This study provides an important insight into the structural requirements of MDMA analogue affinity at both NET and SERT. It is anticipated that these results will facilitate understanding of the likely pharmacological actions of structural analogues of MDMA.

MDMA-like behavioral effects of N-substituted piperazines in the mouse

Few studies have characterized the subjective effects of N-substituted piperazines, but these drugs show potential for abuse in humans, and have often been associated with MDMA ("ecstasy") in this regard. The aim of the present study was to test the capacity of N-substituted piperazines to induce a head twitch response, alter locomotor activity, and induce MDMA-like discriminative stimulus effects in mice. Various doses of l-benzylpiperazine (BZP), 1-(3-trifluoromethylphenyl) piperazine (TFMPP), 1-(3-methoxybenzyl) piperazine (m-MeO-BZP) or meta-chlorophenyl piperazine (m-CPP) were administered to mice to determine the effects on these behavioral endpoints. BZP, but not its meta-methoxyl analogue, increased locomotor activity in a dose-dependent manner; the phenylpiperazines and m-MeO-BZP only decreased locomotor activity. TFMPP was the only compound active in the head twitch assay, eliciting a moderate head twitch response which was comparable to that previously observed with the MDMA enantiomers. BZP, TFMPP and m-CPP fully substituted in S(+)-MDMA-trained animals, but did not elicit significant drug lever responding in mice trained to discriminate R(-)-MDMA. m-MeO-BZP partially substituted for both training drugs. The present results suggest that BZP has stimulant-like effects, and that TFMPP has hallucinogen-like effects. Their structural analogues, however, do not share these behavioral profiles. Further studies into the relationships between the N-substituted piperazines and MDMA are warranted.

Alpha1-adrenergic receptors mediate the locomotor response to systemic administration of (+/-)-3,4-methylenedioxymethamphetamine (MDMA) in rats

The recreational drug 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) increases locomotor activity when administered to rats. Although the published pharmacology of MDMA has focused almost exclusively on the roles of serotonin and dopamine, in vitro studies indicate that MDMA induces serotonin and norepinephrine release with equal potency. The present experiments tested the hypothesis that blockade of alpha(1)-adrenoceptors with systemic or local administration of the antagonist prazosin would attenuate the locomotor response to systemic administration of (+/-)-MDMA. Pretreatment with systemic prazosin (0.5 mg/kg) or microinjections into either the prefrontal cortex or ventral tegmental area completely blocked the locomotor stimulant effects of 5 mg/kg (+/-)-MDMA, assessed using a computerized Behavioral Pattern Monitor. Prazosin was more potent in blocking the locomotor stimulant effects of (+/-)-MDMA than a 2 mg/kg dose of (+)-amphetamine that produced a similar locomotor activity increase. These results indicate that activation of alpha(1)-adrenoceptors in both the prefrontal cortex and ventral tegmental areas modulates the locomotor response to MDMA.

(±)3,4-Methylenedioxyamphetamine elicits action potential bursts in a central snail neuron

The effects of (+/-)3,4-methylenedioxyamphetamine (MDA) were studied in an identifiable RP4 neuron of the African snail, Achatina fulica Ferussac, using the two-electrode voltage-clamp method. The RP4 neuron generated spontaneous action potentials. Extracellular or intracellular application of MDA elicited action potential bursts of the central RP4 neuron. The action potential bursts elicited by MDA were not blocked when neurons were immersed in high-Mg2+ solution, Ca2+-free solution, nor after continuous perfusion with atropine, d-tubocurarine, propranolol, prazosin, haloperidol, sulpiride or methiothepin. Notably, the induction of action potential bursts was blocked by pretreatment with protein kinase C (PKC) inhibitors, chelerythrine and Ro 31-8220, but not by protein kinase A (PKA) inhibitors, KT-5720 and H89, nor by the phospholipase C (PLC) inhibitor, U73122. PKC activators, i.e., phorbol 12,13-dibutyrate (PDBu) and 1-oleoyl-2-acety-sn-glycerol (OAG; a membrane-permeant DAG analog), facilitate the induction of action potential bursts elicited by MDA. Voltage-clamp studies revealed that MDA decreased the delayed rectifying K+ current (I(KD)) of the RP4 neuron. Further, although Ro 31-8220 did not affect the I(KD), Ro 31-8220 decreased the inhibitory effect of MDA on the I(KD). These results suggest that the generation of action potential bursts elicited by MDA was not due to (1) the synaptic effects of neurotransmitters, (2) the cholinergic, adrenergic, dopaminergic or serotoninergic receptors of the excitable membrane. Instead, the MDA-elicited action potential bursts are closely related to PKC activity and the inhibitory effects on the I(KD).

Serotonin and psychostimulant addiction: Focus on 5-HT1A-receptors

Serotonin(1A)-receptors (5-HT(1A)-Rs) are important components of the 5-HT system in the brain. As somatodendritic autoreceptors they control the activity of 5-HT neurons, and, as postsynaptic receptors, the activity in terminal areas. Cocaine (COC), amphetamine (AMPH), methamphetamine (METH) and 3,4-methylenedioxymethamphetamine ("Ecstasy", MDMA) are psychostimulant drugs that can lead to addiction-related behavior in humans and in animals. At the neurochemical level, these psychostimulant drugs interact with monoamine transporters and increase extracellular 5-HT, dopamine and noradrenalin activity in the brain. The increase in 5-HT, which, in addition to dopamine, is a core mechanism of action for drug addiction, hyperactivates 5-HT(1A)-Rs. Here, we first review the role of the various 5-HT(1A)-R populations in spontaneous behavior to provide a background to elucidate the contribution of the 5-HT(1A)-Rs to the organization of psychostimulant-induced addiction behavior. The progress achieved in this field shows the fundamental contribution of brain 5-HT(1A)-Rs to virtually all behaviors associated with psychostimulant addiction. Importantly, the contribution of pre- and postsynaptic 5-HT(1A)-Rs can be dissociated and frequently act in opposite directions. We conclude that 5-HT(1A)-autoreceptors mainly facilitate psychostimulant addiction-related behaviors by a limitation of the 5-HT response in terminal areas. Postsynaptic 5-HT(1A)-Rs, in contrast, predominantly inhibit the expression of various addiction-related behaviors directly. In addition, they may also influence the local 5-HT response by feedback mechanisms. The reviewed findings do not only show a crucial role of 5-HT(1A)-Rs in the control of brain 5-HT activity and spontaneous behavior, but also their complex role in the regulation of the psychostimulant-induced 5-HT response and subsequent addiction-related behaviors.

MDMA (Ecstasy) and human dopamine, norepinephrine, and serotonin transporters: implications for MDMA-induced neurotoxicity and treatment

RATIONALE

3,4-Methylenedioxymethamphetamine (MDMA, designated as "Ecstasy" if illicitly marketed in tablet form) induces significant decrements in neuronal serotonin (5-HT) markers in humans, nonhuman primates, and rats as a function of dosing and dosing regimen. In rats, MDMA-mediated effects are attributed, in part, to selective high-affinity transport of MDMA into 5-HT neurons by the 5-HT transporter (SERT), followed by extensive 5-HT release.

OBJECTIVES

To clarify whether SERT-selective effects of MDMA at human monoamine transporters can account for the reported MDMA-induced selective toxicity of serotonin neurons in primate brain.

METHODS

We investigated the interaction of [(3)H](+/-, RS)- (+, S)- and (-, R)-MDMA with the human SERT, dopamine (DA) transporter (DAT), and norepinephrine (NE) transporter (NET) in stably transfected human embryo kidney (HEK)-293 cells.

RESULTS

The human DAT, NET, and SERT actively transported [(3)H]RS(+/-)-MDMA saturably, stereoselectively, and in a temperature-, concentration-, and transporter-dependent manner. MDMA exhibited the highest affinity for the NET>>SERT>or=DAT, the same rank order for MDMA inhibition of [(3)H]DA, [(3)H]NE, and [(3)H]5-HT transport and stimulated release of the [(3)H]monoamines, which differed from reports derived from rodent monoamine transporters. The extent of MDMA-induced release of 5-HT was higher compared with release of DA or NE.

CONCLUSIONS

The affinity of MDMA for the human SERT in transfected cells does not clarify the apparent selective toxicity of MDMA for serotonin neurons, although conceivably, its higher efficacy for stimulating 5-HT release may be a distinguishing factor. The findings highlight the need to investigate MDMA effects in DAT-, SERT-, and NET-expressing neurons in the primate brain and the therapeutic potential of NET or DAT inhibitors, in addition to SERT-selective inhibitors, for alleviating the pharmacological effects of MDMA.

Reinforcing effects of methylenedioxy amphetamine congeners in rhesus monkeys: are intravenous self-administration experiments relevant to MDMA neurotoxicity?

RATIONALE

Many animal models relevant to the persistent effects of drugs of abuse necessitate the application of interspecies dose scaling procedures to approximate drug administration regimens in humans, but drug self-administration procedures differ in that they allow animal subjects to control their own drug intake.

OBJECTIVES

This report reviews the reinforcing effects of 3,4-methylenedioxymethamphetamine (MDMA), its enantiomers, and several structural analogs in rhesus monkeys, paying particular attention to the pharmacological mechanisms of such reinforcing effects, the development of structure activity relationships among these compounds, the stability of MDMA self-administration behavior over time, and the persistent effects of self-administered MDMA on monoamines.

RESULTS

The methylenedioxy amphetamine congeners MDMA, 3,4-methylenedioxyamphetamine, N-ethyl-3,4-methylenedioxyamphetamine, and N-methyl-1-(3,4-methylenedioxyphenyl)-2-butanamine function as reinforcers in rhesus monkeys, maintaining self-administration behavior greater than that engendered by contingent saline but less than that engendered by traditional psychostimulants. These findings are remarkable as structurally distinct serotonergic hallucinogen-like drugs do not maintain reliable self-administration in laboratory animals. During prolonged MDMA self-administration, MDMA-maintained responding progressively weakens, and MDMA eventually fails to maintain significant self-administration. The neurochemical correlates of this effect have not yet been identified.

CONCLUSIONS

Procedures in which MDMA and related compounds are self-administered can be established in rhesus monkeys. These techniques can be used to engender contingent MDMA exposure without resorting to controversial methods of interspecies dose scaling. As such, further application of self-administration methods may provide important new insights into the persistent effects of MDMA on brain and behavior in nonhuman primates.

Differential contributions of dopamine D1, D2, and D3 receptors to MDMA-induced effects on locomotor behavior patterns in mice

MDMA or 'ecstasy' (3,4-methylenedioxymethamphetamine) is a commonly used psychoactive drug that has unusual and distinctive behavioral effects in both humans and animals. In rodents, MDMA administration produces a unique locomotor activity pattern, with high activity characterized by smooth locomotor paths and perseverative thigmotaxis. Although considerable evidence supports a major role for serotonin release in MDMA-induced locomotor activity, dopamine (DA) receptor antagonists have recently been shown to attenuate these effects. Here, we tested the hypothesis that DA D1, D2, and D3 receptors contribute to MDMA-induced alterations in locomotor activity and motor patterns. DA D1, D2, or D3 receptor knockout (KO) and wild-type (WT) mice received vehicle or (+/-)-MDMA and were tested for 60 min in the behavioral pattern monitor (BPM). D1 KO mice exhibited significant increases in MDMA-induced hyperactivity in the late testing phase as well as an overall increase in straight path movements. In contrast, D2 KO mice exhibited reductions in MDMA-induced hyperactivity in the late testing phase, and exhibited significantly less sensitivity to MDMA-induced perseverative thigmotaxis. At baseline, D2 KO mice also exhibited reduced activity and more circumscribed movements compared to WT mice. Female D3 KO mice showed a slight reduction in MDMA-induced hyperactivity. These results confirm differential modulatory roles for D1 and D2 and perhaps D3 receptors in MDMA-induced hyperactivity. More specifically, D1 receptor activation appears to modify the type of activity (linear vs circumscribed), whereas D2 receptor activation appears to contribute to the repetitive circling behavior produced by MDMA.

Association of caffeine to MDMA does not increase antinociception but potentiates adverse effects of this recreational drug

Ecstasy (MDMA) street tablets often contain several other compounds in addition to MDMA, particularly caffeine. Then, it becomes necessary to study the consequences of caffeine plus MDMA combination. MDMA (1 mg/kg) elicited an analgesic response both at the spinal and supraspinal levels. However, when associated, MDMA and caffeine did not show any synergistic interaction. When caffeine was administered prior to MDMA, a potentiation of locomotor activity was observed, which consisted in an increase in maximal values and in a prolonged time of activity. In the neurotoxicity studies, a hyperthermic effect of MDMA was observed. Although caffeine alone failed to alter body temperature, it potentiated MDMA-induced hyperthermia. This association also significantly increased MDMA lethality (from 22% to 34%). Following administration of MDMA to rats, there was a persistent decrease in the number of serotonin transporter sites in the cortex, striatum and hippocampus, which was potentiated by caffeine co-treatment. This MDMA toxicity in rats was accompanied by a transient dopaminergic impairment in the striatum, measured as decreased [(3)H]WIN35428 binding sites, by 31% 3 days after treatment, which was not modified by caffeine. A transient down-regulation of 5-HT(2) receptors occurred in the cortex of MDMA-treated rats, whose recovery was slowed by co-treatment with caffeine. In conclusion, the association of MDMA with caffeine does not generate any beneficial effects at the antinociceptive level. The acute effects stemming from this association, in tandem with the final potentiation of serotonergic terminals injury, provide evidence of the potentially greater long-term adverse effects of this particular recreational drug combination.

Acute effects of 3,4-methylenedioxymethamphetamine (MDMA) on behavioral measures of impulsivity: alone and in combination with alcohol

The use of 3,4-methylenedioxymethamphetamine (MDMA) has frequently been associated with increased levels of impulsivity during abstinence. The effects of MDMA on measures of impulsivity, however, have not yet been studied during intoxication. The present study was designed to assess the acute effects of MDMA and alcohol, alone and in combination, on behavioral measures of impulsivity and risk-taking behavior. A total of 18 recreational users of MDMA entered a double-blind placebo-controlled six-way crossover study. The treatments consisted of MDMA 0, 75, and 100 mg with and without alcohol. Alcohol dosing was designed to achieve a peak blood alcohol concentration (BAC) of about 0.06 g/dl during laboratory testing. Laboratory tests of impulsivity were conducted between 1.5 and 2 h post-MDMA and included a stop-signal task, a go/no-go task, and the Iowa gambling task. MDMA decreased stop reaction time in the stop-signal task indicating increased impulse control. Alcohol increased the proportion of commission errors in the stop-signal task and the go/no-go task. Signal detection analyses of alcohol-induced commission errors indicated that this effect may reflect impairment of perceptual or attentive processing rather than an increase of motor impulsivity per se. Performance in the Iowa gambling task was not affected by MDMA and alcohol, but there was a nonsignificant tendency towards improvement following alcohol intake. None of the behavioral measures of impulsivity showed a MDMA x alcohol interaction effect. The lack of interaction indicated that the CNS stimulant effects of MDMA were never sufficient to overcome alcohol-induced impairment of impulse control or risk-taking behavior.

Differences in the in vivo dynamics of neurotransmitter release and serotonin uptake after acute para-methoxyamphetamine and 3,4-methylenedioxymethamphetamine revealed by chronoamperometry

Illicit use of p-methoxyamphetamine (PMA) is rapidly increasing. However, little is known about the acute effects of PMA on neurotransmission in vivo. High-speed chronoamperometry was used to monitor neurotransmitter release and clearance in anesthetized rats after local application of PMA or 3,4-methylenedioxymethamphetamine (MDMA). In striatum, PMA caused less neurotransmitter release than MDMA. PMA-evoked release could be partially blocked by pre-treatment with a serotonin (5-HT) reuptake inhibitor, suggesting that evoked 5-HT release contributed to the electrochemical signal and was mediated by the 5-HT transporter (SERT). MDMA-evoked release was not blocked by a SERT inhibitor, suggesting that primarily DA was released. To study the effect of these amphetamines on clearance of 5-HT mediated specifically by the SERT, clearance of exogenously applied 5-HT was measured in the CA3 region of the hippocampus. In contrast to the striatum where 5-HT is cleared by both the SERT and the dopamine transporter (DAT), 5-HT is cleared primarily by the SERT in the CA3 region. This is also a region where neither PMA nor MDMA evoked release of neurotransmitter. The maximal inhibition of 5-HT clearance was greater after PMA than MDMA. These data demonstrate in vivo (1) brain region variability in the ability of PMA and MDMA to evoke release of neurotransmitter; (2) that clearance of 5-HT in the striatum is mediated by both the SERT and the DAT; (3) distinct differences in the amount and nature of neurotransmitter released in the striatum after local application of PMA and MDMA and (4) that PMA is a more efficacious inhibitor of 5-HT clearance in the hippocampus than MDMA. These fundamental differences may account for the more severe adverse reactions seen clinically after PMA, compared to MDMA.

Carvedilol reverses hyperthermia and attenuates rhabdomyolysis induced by 3,4-methylenedioxymethamphetamine (MDMA, Ecstasy) in an animal model

OBJECTIVE

Hyperthermia is a potentially fatal manifestation of severe 3,4-methylenedioxymethamphetamine (MDMA, Ecstasy) intoxication. No proven effective drug treatment exists to reverse this potentially life-threatening hyperthermia, likely because mechanisms of peripheral thermogenesis are poorly understood. Using a rat model of MDMA hyperthermia, we evaluated the acute drug-induced changes in plasma catecholamines and used these results as a basis for the selection of drugs that could potentially reverse this hyperthermia.

DESIGN

Prospective, controlled, randomized animal study.

SETTING

A research institute laboratory.

SUBJECTS

Male, adult Sprague-Dawley rats.

INTERVENTIONS

Based on MDMA-induced changes in plasma catecholamine levels, rats were subjected to the nonselective (beta1 + beta2) adrenergic receptor antagonists propranolol or nadolol or the alpha1- + beta1,2,3-adrenergic receptor antagonist carvedilol before or after a thermogenic challenge of MDMA.

MEASUREMENT AND MAIN RESULTS

Plasma catecholamines levels 30 mins after MDMA (40 mg/kg, subcutaneously) were determined by high-pressure liquid chromatography and electrochemical detection. Core temperature was measured by a rectal probe attached to a thermocouple. Four hours after MDMA treatment, blood was drawn and serum creatine kinase levels were measured as a marker of rhabdomyolysis using a Vitros analyzer. MDMA induced a 35-fold increase in norepinephrine levels, a 20-fold increase in epinephrine, and a 2.4-fold increase in dopamine levels. Propranolol (10 mg/kg, intraperitoneally) or nadolol (10 mg/kg, intraperitoneally) administered 30 mins before MDMA had no effect on the thermogenic response. In contrast, carvedilol (5 mg/kg, intraperitoneally) administered 15 mins before or after MDMA prevented this hyperthermic response. Moreover, when administered 1 hr after MDMA, carvedilol completely reversed established hyperthermia and significantly attenuated subsequent MDMA-induced creatine kinase release.

CONCLUSION

These data show that alpha1 and beta3-adrenergic receptors may contribute to the mediation of MDMA-induced hyperthermia and that drugs targeting these receptors, such as carvedilol, warrant further investigation as novel therapies for the treatment of psychostimulant-induced hyperthermia and its sequelae.

Discovery of Novel Trisubstituted Asymmetric Derivatives of (2S,4R,5R)-2-benzhydryl-5-benzylaminotetrahydropyran-4-ol, Exhibiting High Affinity for Serotonin and Norepinephrine Transporters in a Stereospecific Manner

In our structure-activity relationship study on 3,6-disubstituted pyran derivatives, we have carried out asymmetric synthesis and biological characterization of trisubstituted (2S,4R,5R)-2-benzhydryl-5-benzylaminotetrahydropyran-4-ol and (3S,4R,6S)-6-benzhydryl-4-benzylaminotetrahydropyran-3-ol derivatives and their enantiomers. All synthesized derivatives were tested for their affinities for the dopamine transporter (DAT), serotonin transporter (SERT), and norepinephrine transporter (NET) in the brain by measuring their potency in inhibiting the uptake of [(3)H]DA, [(3)H]-5-HT, and [(3)H]NE, respectively. Compounds were also tested for their binding affinity at the DAT by their inhibition of [(3)H]WIN 35,428. Biological results indicated that regioselectivity and stereoselectivity played important roles in determining activity for monoamine transporters as only (-)-isomers of 2-benzhydryl-5-benzylaminotetrahydropyran-4-ol derivatives exhibited appreciable potency for the monoamine transporters, in particular for the SERT and NET. Among the active analogues, (-)-9d exhibited potent and selective affinity at the NET (K(i), [(3)H]NE = 4.92 nM; DAT/NET = 91 and SERT/NET = 140). One of the derivatives with p-methoxybenzyl substitution, (-)-9a, was potent at both SERT and NET (K(i), [(3)H]-5-HT = 25.9 and [(3)H]NE = 15.8 nM, respectively). In the active analogue series ((-)-9a-(-)-9e), a cis-relationship between the biphenyl and the amino moiety was maintained for the SERT and NET interactions, as was observed with our earlier 3,6-disubstituted pyran compounds for the DAT interaction. To the best of our knowledge, this current series of compounds represents a novel class of pyran derivatives as blockers for monoamine transporters.

3,4-Methylenedioxymethamphetamine counteracts akinesia enantioselectively in rat rotational behavior and catalepsy

We have shown recently that 3,4-methylenedioxymethamphetamine (MDMA) has symptomatic antiparkinsonian activity in rodent models of Parkinson's disease. In search of its mechanism of action, we further investigated the enantiomers of MDMA in the rotational behavioral model and catalepsy test. Catalepsy testing was done in drug-naive unlesioned animals. The parkinsonian symptoms rigor and akinesia (i.e., catalepsy) were induced by intraperitoneal administration of haloperidol 0.5 mg/kg and measured repeatedly as descent latency from a horizontal bar and a vertical grid. MDMA and both its enantiomers were effective in counteracting haloperidol-induced catalepsy, but if given as racemic, the effects were more pronounced than with the enantiomers. For testing of rotational behavior, male Sprague Dawley rats were lesioned unilaterally with 6-hydroxydopamine (6-OHDA) at the medial forebrain bundle. Administration of S-MDMA (5 mg/kg) produced ipsilateral rotations. R-MDMA was far less effective in inducing ipsilateral rotations in 6-OHDA unilaterally lesioned rats, but when S-MDMA was given additionally rotations immediately increased. Regarding their overall antiparkinsonian effects, the S-enantiomer of MDMA was more effective than its R-congener. R-MDMA was able to increase the actions of S-MDMA.