Disposition of methylenedioxymethamphetamine and three metabolites in the brains of different rat strains and their possible roles in acute serotonin depletion

The importance of heterogeneous nuclear ribonucleoprotein K on cytochrome P450 2D2 gene regulation: its binding is reduced in Dark Agouti rats

Cytochrome P450 (P450) 2D2 (CYP2D2) enzyme is known to metabolize the majority of typical substrates of the human CYP2D6 enzyme, which is the most extensively characterized polymorphic drug-metabolizing enzyme. Despite its impact on drug metabolism in rats, the transcriptional regulation of CYP2D2 remains to be elucidated. We clarified the molecular mechanism of CYP2D2 gene expression. The CYP2D2 gene was positively regulated by the poly(C)-binding protein heterogeneous nuclear ribonucleoprotein K (hnRNP K) through a transcriptional regulatory element located in the 5'-flanking region from -94 to -113. To date, nothing is known about the potential role of hnRNP K in P450 gene regulation. Thus, this is the first report that hnRNP K protein is involved in CYP2D2 gene regulation. Furthermore, we elucidated the genetic basis of the extremely low expression of CYP2D2 mRNA in Dark Agouti (DA) rats. Because of its relatively low abundance, DA rats have been frequently used for the study of CYP2D substrate metabolism as the animal model of the poor metabolizer phenotype for CYP2D6 compared with Sprague-Dawley rats as an extensive metabolizer phenotype. We found a single substitution within the transcriptional regulatory element of the CYP2D2 gene in DA rats. The mutation was detected in the polypyrimidine sequence that is the preferred binding site for hnRNP K protein. The mutation within the transcriptional regulatory element attenuated the binding of hnRNP K protein. In conclusion, decreased recruitment of hnRNP K protein to the mutated sequence causes the low expression of CYP2D2 mRNA in DA rats.

Discriminative stimulus effects of 3,4-methylenedioxymethamphetamine and its enantiomers in mice: pharmacokinetic considerations

3,4-Methylenedioxymethamphetamine (MDMA) is a drug of abuse with mixed stimulant- and hallucinogen-like effects. The aims of the present studies were to establish discrimination of S(+)-MDMA, R(-)-MDMA, or their combination as racemic MDMA in separate groups of mice to assess cross-substitution tests among all three compounds, to determine the time courses of the training doses, to assess pharmacokinetic variables after single injections and after cumulative dosing, and to define the metabolic dispositions of MDMA enantiomers and their metabolites. All three forms of MDMA served as discriminative stimuli, and with the exception of R(-)-MDMA in mice trained to discriminate the racemate, compounds substituted for one another. The onset of interoceptive effects for S(+)-MDMA and racemic MDMA were faster than for R(-)-MDMA, and the duration of discriminative stimulus effects was shortest for R(-)-MDMA. S(+)-MDMA and its metabolites were found in higher concentrations than R(-)-MDMA and its metabolites after a bolus dose of racemic MDMA. The N-dealkylation pathway is favored in mouse plasma with MDA as the main metabolite formed. Cumulative doses of MDMA lead to higher plasma concentrations compared with an equivalent single dose. 3,4-Methylenedioxyamphetamine (MDA) concentrations are lower after the cumulative dose compared with the single dose, which, coupled with the nonlinearity observed in MDMA pharmacokinetics after increased doses of racemic MDMA, suggests autoinhibition (or saturation) of MDMA metabolism in mice. In total, these studies suggest that the discriminative stimulus effects of racemic MDMA are perhaps driven by accumulation of S(+)-MDMA and S(+)-MDA in the mouse.

Neural and cardiac toxicities associated with 3,4-methylenedioxymethamphetamine (MDMA)

(+/-)-3,4-Methylenedioxymethamphetamine (MDMA) is a commonly abused illicit drug which affects multiple organ systems. In animals, high-dose administration of MDMA produces deficits in serotonin (5-HT) neurons (e.g., depletion of forebrain 5-HT) that have been viewed as neurotoxicity. Recent data implicate MDMA in the development of valvular heart disease (VHD). The present paper reviews several issues related to MDMA-associated neural and cardiac toxicities. The hypothesis of MDMA neurotoxicity in rats is evaluated in terms of the effects of MDMA on monoamine neurons, the use of scaling methods to extrapolate MDMA doses across species, and functional consequences of MDMA exposure. A potential treatment regimen (l-5-hydroxytryptophan plus carbidopa) for MDMA-associated neural deficits is discussed. The pathogenesis of MDMA-associated VHD is reviewed with specific reference to the role of valvular 5-HT(2B) receptors. We conclude that pharmacological effects of MDMA occur at the same doses in rats and humans. High doses of MDMA that produce 5-HT depletions in rats are associated with tolerance and impaired 5-HT release. Doses of MDMA that fail to deplete 5-HT in rats can cause persistent behavioral dysfunction, suggesting even moderate doses may pose risks. Finally, the MDMA metabolite, 3,4-methylenedioxyamphetamine (MDA), is a potent 5-HT(2B) agonist which could contribute to the increased risk of VHD observed in heavy MDMA users.

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

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

Positron emission tomographic studies of brain dopamine and serotonin transporters in abstinent (+/-)3,4-methylenedioxymethamphetamine ("ecstasy") users: relationship to cognitive performance

BACKGROUND

(+/-)3,4-Methylenedioxymethamphetamine (MDMA, "ecstasy") is a recreational drug and brain serotonin (5-HT) neurotoxin. Under certain conditions, MDMA can also damage brain dopamine (DA) neurons, at least in rodents. Human MDMA users have been found to have reduced brain 5-HT transporter (SERT) density and cognitive deficits, although it is not known whether these are related. This study sought to determine whether MDMA users who take closely spaced sequential doses, which engender high plasma MDMA concentrations, develop DA transporter (DAT) deficits, in addition to SERT deficits, and whether there is a relationship between transporter binding and cognitive performance.

MATERIALS AND METHODS

Sixteen abstinent MDMA users with a history of using sequential MDMA doses (two or more doses over a 3- to 12-h period) and 16 age-, gender-, and education-matched controls participated. Subjects underwent positron emission tomography with the DAT and SERT radioligands, [11C]WIN 35,428 and [11C]DASB, respectively. Subjects also underwent formal neuropsychiatric testing.

RESULTS

MDMA users had reductions in SERT binding in multiple brain regions but no reductions in striatal DAT binding. Memory performance in the aggregate subject population was correlated with SERT binding in the dorsolateral prefrontal cortex, orbitofrontal cortex, and parietal cortex, brain regions implicated in memory function. Prior exposure to MDMA significantly diminished the strength of this relationship.

CONCLUSIONS

Use of sequential MDMA doses is associated with lasting decreases in brain SERT, but not DAT. Memory performance is associated with SERT binding in brain regions involved in memory function. Prior MDMA exposure appears to disrupt this relationship. These data are the first to directly relate memory performance to brain SERT density.

Fluoxetine Pretreatment Effects Pharmacokinetics of 3,4‐Methylenedioxymethamphetamine (MDMA, ECSTASY) in Rat

Fluoxetine has been shown to provide protection from MDMA induced long term neurotoxicity. The purpose of this investigation is to evaluate the pharmacokinetic drug interaction between MDMA and fluoxetine and also to determine the role of P-glycoprotein (P-gp) on mediating drug-drug interactions with MDMA. Bi-directional transport studies were conducted across MDCK-MDR1 and Caco-2 monolayers. MDMA brain and plasma levels were measured in P-gp deficient [mdr1a(-/-)] and normal [mdr1a(+/+)] mice after a 5 mg/kg i.p. dose of MDMA. Sprague-Dawley rats were pretreated with fluoxetine (4 days, 10 mg/kg, i.p.) or saline followed by MDMA (10 mg/kg, p.o.) and brain and plasma samples were collected over 10 h. MDMA and its active metabolite MDA were quantified using a HPLC method with fluorescence detection. In transport studies MDMA exhibited high permeability with essentially unpolarized transport. No significant difference in MDMA and MDA brain levels were seen in P-gp deficient versus normal mice. Pretreatment of rats with fluoxetine resulted in an increase in MDMA (1.4-fold) and MDA (1.5-fold) exposure in both brain and plasma. Elimination half-life was increased for MDMA (2.4 vs. 4.9 h) and MDA (1.8 vs. 8.2 h) with fluoxetine pretreatment. P-gp does not play a physiologically relevant role in absorption and distribution of MDMA, hence this transporter may not have a role in drug-drug interactions with MDMA. Fluoxetine pretreatment to provide protection from MDMA induced long term neurotoxicity decreases elimination of MDMA and MDA and may lead to enhanced risk of MDMA acute toxic effects. Overall, our results indicate that caution need to be practiced when recommending fluoxetine as an agent to provide protection from MDMA induced long term neurotoxicity.

Different oxidative profile and nicotinic receptor interaction of amphetamine and 3,4-methylenedioxy-methamphetamine

d-Amphetamine (AMPH) and MDMA increased intracellular production of reactive oxygen species (ROS) in isolated mouse striatal synaptosomes. MDMA showed a maximal oxidative effect at 50-100 microM. However, for AMPH a double maximum was obtained, the first between 0.1 and 1 microM and the second at 1mM. No oxidative effect was present in synaptosomes from reserpinized mice. Cocaine and l-deprenyl inhibited MDMA and AMPH (0.1 microM) ROS production but not that of AMPH at a higher concentration (1mM). When this high concentration was used, its oxidative effect was abolished by a phospholipase A(2) inhibitor. Delta(9)-Tetrahydrocannabinol fully prevented the oxidative effect of AMPH and MDMA, by a CB(1) receptor-independent mechanism, as did it NPC 15437 and genistein. The pro-oxidative effect induced by AMPH and MDMA showed a strong dependence on calcium (extracellular and from internal stores) and also was inhibited by nicotinic receptor (nAChR) antagonists dihydro-beta-erythroidine, methyllycaconitine (MLA) and alpha-bungarotoxin. MDMA displaced [(3)H]epibatidine and [(3)H]MLA binding with higher affinity than AMPH. Both amphetamines competitively displaced [(3)H]epibatidine from heteromeric receptors but results obtained from [(3)H]MLA binding demonstrated a non-competitive profile. Preincubation of PC12 cells with AMPH or MDMA reduced [(3)H]dopamine uptake. For MDMA, this effect was prevented by MLA. To summarize, comparing AMPH and MDMA we have demonstrated that these drugs induce an oxidative effect dependent on drug concentration and also reduce dopamine uptake. Processes that are known to affect dopamine transporter functionality also seem to modulate amphetamine derivatives-induced ROS production. For MDMA, acute effects tested are blocked by nAChR antagonists, which points to the possibility that these antagonists could be used to treat some of the adverse effects described in MDMA abusers. Conversely, no implication of nicotinic receptors has been proved for AMPH-induced effects at concentrations achievable in CNS after its administration.

Ambient Temperature Effects on 3,4-Methylenedioxymethamphetamine-Induced Thermodysregulation and Pharmacokinetics in Male Monkeys

Changes in ambient temperature are known to alter both the hyperthermic and the serotonergic consequences of 3,4-methylenedioxymethamphetamine (MDMA). Metabolism of MDMA has been suggested to be a requisite for these neurotoxic effects, whereas the hyperthermic response is an important contributing variable. The aim of the present study was to investigate the interaction between ambient temperature, MDMA-induced thermodysregulation, and its metabolic disposition in monkeys. MDMA (1.5 mg/kg i.v.) was administered noncontingently at cool (18 degrees C; n = 5), room (24 degrees C; n = 7), and warm (31 degrees C; n = 7) ambient temperatures. For 240 min following MDMA administration, core temperature was recorded and blood samples were collected for analysis of MDMA and its metabolites 3,4-dihydroxymethamphetamine (HHMA), 3,4-dihydroxyamphetamine, and 3,4-methylenedioxyamphetamine (MDA). A dose of 1.5 mg/kg MDMA induced a hypothermic response at 18 degrees C, a hyperthermic response at 31 degrees C, and did not significantly change core temperature at 24 degrees C. Regardless of ambient temperature, plasma MDMA concentrations reached maximum within 5 min, and HHMA was a major metabolite. Curiously, the approximate elimination half-life (t(1/2)) of MDMA at 18 degrees C (136 min) and 31 degrees C (144 min) was increased compared with 24 degrees C (90 min) and is most likely because of volume of distribution changes induced by core temperature alterations. At 18 degrees C, there was a significantly higher MDA area under the concentration-time curve (AUC) and a trend for a lower HHMA AUC compared with 24 degrees C and 31 degrees C, suggesting that MDMA disposition was altered. Overall, induction of hypothermia in a cool environment by MDMA may alter its disposition. These results could have implications for MDMA-induced serotonergic consequences.

Ecstasy induces apoptosis via 5-HT2A-receptor stimulation in cortical neurons

3,4-Methylenedioxymethamphetamine (MDMA or "Ecstasy") is a psychoactive and hallucinogenic drug of abuse. MDMA has been shown to produce neurotoxicity both in animals and humans. MDMA and other amphetamines induce serotonergic and dopaminergic terminal neurotoxicity and also neurodegeneration in areas including the cortex, hippocampus, striatum and thalamus. Herein, we investigated the mechanisms involved in MDMA-induced neurotoxicity to neuronal serum free cultures from rat cortex. The hyperthermic effect produced by MDMA has been shown to be a clinically relevant aspect for the neurotoxic events. Thus, MDMA-induced toxicity to cortical neurons was evaluated both under normothermic (36.5 degrees C) and hyperthermic (40 degrees C) conditions. Our findings showed that MDMA produced neuronal apoptosis, accompanied by activation of caspase 3, in a concentration dependent manner. MDMA neurotoxicity was completely prevented by pre-treatment with a 5-HT(2A)-receptor antibody, which acted as an "irreversible non-competitive antagonist" of this receptor. Furthermore, MDMA depleted intracellular glutathione (GSH) levels in a concentration dependent manner, an effect that was attenuated by Ketanserin, a competitive 5-HT(2A)-receptor antagonist. Accordingly, N-acetylcysteine, an antioxidant and GSH precursor, also reduced MDMA-induced toxicity. Specific inhibitors of the inducible and neuronal nitric oxide synthase (NOS) partially prevented MDMA neurotoxicity, ascertaining the involvement of reactive nitrogen species, in the toxic effect. In conclusion, direct MDMA 5-HT(2A)-receptor stimulation produces intracellular oxidative stress that leads to neuronal apoptosis accompanied by caspase 3 activation.

Ethanol-MDMA interactions in rats: the importance of interval between repeated treatments in biobehavioral tolerance and sensitization to the combination

RATIONALE

In our previous work, we showed that ethanol (EtOH) potentiates 3,4-methylenedioxymethamphetamine (MDMA)-induced hyperlocomotion while protecting against its hyperthermic effects. Whereas the effect on activity were found on all days (although declining over the three first days), the protection against hyperthermia completely disappeared on the second day. The latter effect was previously thought to reflect tolerance to ethanol or the combination, per se.

OBJECTIVE

In the present study, we changed the treatment regimen to irregular and longer intervals between treatments (48, 120, and again 48 h) to check if tolerance was still observed.

RESULTS

We found progressive sensitization of locomotor activity to EtOH (1.5 g/kg, i.p.)+MDMA (6.6 mg/kg, i.p.), and a partial EtOH protection against MDMA-induced hyperthermia that persisted after the first drug challenge day. When the monoamine neurotransmitters, dopamine, and serotonin were assessed 2 weeks after treatment, we found no consistent effect on the concentration of any of these neurotransmitters, whatever the treatment. Similarly, we found that regional brain concentrations of MDMA were not significantly affected by EtOH at a 45-min post-treatment delay; however, the overall ratio of the metabolite 3,4-methylenedioxyamphetamine (MDA) to MDMA was lower (overall, -16%) in animals treated with the combination compared to MDMA alone, indicating possible contribution of pharmacokinetic factors. This difference was especially marked in the striatum (-25%).

CONCLUSIONS

These findings shed new light on the consequences of EtOH-MDMA, taken together at a nearly normal ambient temperature, both in terms of motivation and potential risks for recreational drug users.

The effects of co-administration of 3,4-methylenedioxymethamphetamine (“ecstasy”) or para-methoxyamphetamine and moclobemide at elevated ambient temperatures on striatal 5-HT, body temperature and behavior in rats

We have recently demonstrated that co-administration of 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy") with the reversible monoamine oxidase type A (MAO-A) inhibitor moclobemide at an ambient temperature of 22 degrees C significantly increases striatal 5-HT outflow and 5-HT-mediated behaviors. In the present study, using microdialysis, we examined the effects of co-administration of MDMA or para-methoxyamphetamine (PMA) with moclobemide on striatal 5-HT outflow at the elevated ambient temperatures of 30 degrees C. Samples were collected every 30 min for 4 h and analyzed by high-performance liquid chromatography assay with electrochemical detection (HPLC-ED). 5-HT-mediated effects on body temperature and behavior were also recorded. Rats were treated with either saline or 20 mg/kg (i.p.) moclobemide, followed by 10 mg/kg (i.p.) MDMA, 10 mg/kg (i.p.) PMA or saline 60 min later. Both MDMA and PMA produced significant increases in 5-HT outflow (370% peak and 309% peak, respectively, P<0.05). MDMA and PMA significantly increased body temperature (+2.0 degrees C and +2.1 degrees C, respectively, P<0.01) and drug-related behaviors (P<0.05). When MDMA or PMA was co-administered with moclobemide, additional significant increases were seen in 5-HT outflow (850% peak, P<0.01 and 1450% peak, P<0.001, respectively) and only MDMA showed additional significant increase in body temperature (+5.0 degrees C, P<0.001). No additional increases were seen in behavioral activity. When moclobemide was co-administered with MDMA, sustained increases in body temperature were recorded that were significantly higher than with MDMA alone and such increases were not observed in our previous study at normal room temperature. Our results suggest greater risk of MDMA-induced adverse effects on body temperature regulation, compared with PMA, when used in combination with moclobemide at elevated ambient temperatures.

Are there sex differences associated with the effects of ecstasy/3,4-methylenedioxymethamphetamine (MDMA)?

Sex has been identified as an important factor in moderating the effects of several drugs of abuse. Given the increasing popularity of ecstasy (3,4-methylenedioxymethamphetamine [MDMA]) use, it is important for researchers and clinicians to understand the factors that may influence its pharmacological actions to improve education, harm reduction and treatment efforts. This review focuses on preclinical and clinical research that examines the role of sex as an independent variable in the effects of ecstasy/MDMA. A systematic search of PsycINFO and MEDLINE electronic databases from 1966 to April 2006 was conducted. Both preclinical and clinical studies show a sexually dimorphic pattern in the acute, subacute and possibly long-term effects of ecstasy/MDMA. Specifically, adult females are more sensitive than males to the acute and subacute physical and psychological effects of ecstasy/MDMA and long-term alterations in aspects of 5-HT functioning. Conversely, males are more sensitive to the acute physiological effects of ecstasy/MDMA. These findings are consistent with research outcomes reported for other substances such as amphetamines and cocaine. Potential reasons for these sex differences and directions for future research are discussed.

3,4-Methylenedioxymethamphetamine (MDMA) neurotoxicity in rats: a reappraisal of past and present findings

RATIONALE

3,4-Methylenedioxymethamphetamine (MDMA) is a widely abused illicit drug. In animals, high-dose administration of MDMA produces deficits in serotonin (5-HT) neurons (e.g., depletion of forebrain 5-HT) that have been interpreted as neurotoxicity. Whether such 5-HT deficits reflect neuronal damage is a matter of ongoing debate.

OBJECTIVE

The present paper reviews four specific issues related to the hypothesis of MDMA neurotoxicity in rats: (1) the effects of MDMA on monoamine neurons, (2) the use of "interspecies scaling" to adjust MDMA doses across species, (3) the effects of MDMA on established markers of neuronal damage, and (4) functional impairments associated with MDMA-induced 5-HT depletions.

RESULTS

MDMA is a substrate for monoamine transporters, and stimulated release of 5-HT, NE, and DA mediates effects of the drug. MDMA produces neurochemical, endocrine, and behavioral actions in rats and humans at equivalent doses (e.g., 1-2 mg/kg), suggesting that there is no reason to adjust doses between these species. Typical doses of MDMA causing long-term 5-HT depletions in rats (e.g., 10-20 mg/kg) do not reliably increase markers of neurotoxic damage such as cell death, silver staining, or reactive gliosis. MDMA-induced 5-HT depletions are accompanied by a number of functional consequences including reductions in evoked 5-HT release and changes in hormone secretion. Perhaps more importantly, administration of MDMA to rats induces persistent anxiety-like behaviors in the absence of measurable 5-HT deficits.

CONCLUSIONS

MDMA-induced 5-HT depletions are not necessarily synonymous with neurotoxic damage. However, doses of MDMA which do not cause long-term 5-HT depletions can have protracted effects on behavior, suggesting even moderate doses of the drug may pose risks.

Sex differences in the neurochemical and functional effects of MDMA in Sprague-Dawley rats

RATIONALE

3,4-Methylenedioxymethamphetamine (MDMA; "Ecstasy") use has been associated with acute toxicities and persistent depletion of the neurotransmitter serotonin (5-HT).

OBJECTIVES

This study investigates whether sex differences in the acute and long-term effects of MDMA exist.

METHODS

Male and female rats received saline or 15 mg/kg MDMA, ip, bid for 4 days. Temperature was monitored on days 1 and 4. Locomotor activity was measured in a second cohort of animals on days 1 and 4 and after recovery on day 14. The effects of MDMA on performance in a plus maze task and brain levels of serotonin (5-HT) and the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) were determined in a third cohort of animals 2 weeks after the last MDMA treatment.

RESULTS

Locomotor activity and temperature increased after MDMA administration on day 1. The drug-induced increases in temperature but not locomotion attenuated with repeated MDMA administration. Male and female MDMA-treated rats spent less time in the open arms of the elevated plus maze and had less 5-HT and 5-HIAA in all brain regions 2 weeks after the end of treatment. Temperature effects of MDMA and persistent effects on plus maze and brain serotonin content were similar in males and females. In contrast, females exhibited markedly greater locomotor stimulation after acute MDMA and also showed sensitization to an acute challenge 2 weeks later.

CONCLUSIONS

MDMA elicits substantially greater locomotor activation in female rats than in males, but persistent effects on anxiety and serotonin content were similar in males and females.

Binge administration of 3,4-methylenedioxymethamphetamine (“ecstasy”) impairs the survival of neural precursors in adult rat dentate gyrus

3,4-Methylenedioxymethamphetamine (MDMA) is a potent stimulant and hallucinogenic drug whose ability to regulate neurogenesis in the adult has not been previously investigated. We used 5'-bromo-2-deoxyuridine (BrdU) and Ki-67 as mitotic markers, and doublecortin (DCX) as a marker of immature neurons, to study proliferation, survival and maturation of adult-generated cells in the dentate gyrus (DG) of the hippocampus following binge administration of MDMA (8 injections of 5 mg/kg at 6 h intervals). The results showed that MDMA treatment did not affect cytogenesis in the DG, but significantly decreased the survival rate of cells incorporated after 2 weeks to the granular layer of the DG by ca. 50%, and of those remaining in the subgranular layer by ca. 30%. Two weeks after exposure to MDMA the length of dendritic arbors and the number of dendritic branches of immature DCX+ neurons were nearly identical to those of control rats, as was the level of colocalization of BrdU with DCX. These results demonstrate that binge MDMA administration does not affect the proliferation rates of progenitor cells in the DG, but has deleterious effects on adult neurogenesis by impairing the short-term survival of vulnerable neural precursors.

MDMA-induced neurotoxicity: long-term effects on 5-HT biosynthesis and the influence of ambient temperature

1. 3,4-Methylenedioxymethamphetamine (MDMA or 'ecstasy') decreases the 5-HT concentration, [3H]-paroxetine binding and tryptophan hydroxylase activity in rat forebrain, which has been interpreted as indicating 5-HT neurodegeneration. This has been questioned, particularly the 5-HT loss, as MDMA can also inhibit tryptophan hydroxylase. We have now evaluated the validity of these parameters as a reflection of neurotoxicity. 2. Male DA rats were administered MDMA (12.5 mg kg(-1), i.p.) and killed up to 32 weeks later. 5-HT content and [3H]-paroxetine binding were measured in the cortex, hippocampus and striatum. Parallel groups of treated animals were administered NSD-1015 for determination of in vivo tryptophan hydroxylase activity and 5-HT turnover rate constant. 3. Tissue 5-HT content and [3H]-paroxetine binding were reduced in the cortex (26-53%) and hippocampus (25-74%) at all time points (1, 2, 4, 8 and 32 weeks). Hydroxylase activity was similarly reduced up to 8 weeks, but had recovered at 32 weeks. The striatal 5-HT concentration and [3H]-paroxetine binding recovered by week 4 and hydroxylase activity after week 1. In all regions, the reduction in 5-HT concentration did not result in an altered 5-HT synthesis rate constant. 4. Administering MDMA to animals when housed at 4 degrees C prevented the reduction in [3H]-paroxetine binding and hydroxylase activity observed in rats housed at 22 degrees C, but not the reduction in 5-HT concentration. 5. These data indicate that MDMA produces long-term damage to serotoninergic neurones, but this does not produce a compensatory increase in 5-HT synthesis in remaining terminals. It also highlights the fact that measurement of tissue 5-HT concentration may overestimate neurotoxic damage.

MDMA administration to pregnant Sprague-Dawley rats results in its passage to the fetal compartment

Recent investigations have demonstrated that prenatal 3,4-methylenedeoxymethamphetamine (MDMA; ecstasy) exposure in rats results in significant and persistent changes in the developing brain. However, no published pharmacokinetic studies exist demonstrating that MDMA administered during pregnancy passes to the fetal compartment. This leaves open the question whether MDMA is directly acting on the fetal brain to produce the observed changes in previous studies, or whether such effects are an indirect result of MDMA administration to the pregnant dam. Therefore, pregnant rats were administered a single dose of MDMA (15 mg/kg, subcutaneous) at embryonic day 14 (E14) and the levels of MDMA and its metabolite 3,4-methylenedioxyamphetamine (MDA) were quantified in maternal plasma, amniotic fluid, and fetal brain over 8 h by HPLC. The time course of MDMA and MDA metabolism was reliable and reproducible in all tissues. There was a strong correlation between fetal amniotic fluid and fetal brain suggesting that amniotic fluid could be used to reliably estimate fetal brain levels without directly utilizing fetal brain tissue. These data also provide a framework for subsequent in vitro cell culture studies using biologically relevant MDMA doses.

L-tyrosine contributes to (+)-3,4-methylenedioxymethamphetamine-induced serotonin depletions

The specific mechanisms underlying (+)-3,4-methylenedioxymethamphetamine (MDMA)-induced damage to 5-HT terminals are unknown. Despite the hypothesized role for dopamine (DA) and DA-derived free radicals in mediating this damage, it remains unclear why MDMA produces long-term depletions of 5-HT in brain regions that are sparsely innervated by DA neurons. We hypothesized that the precursor to DA biosynthesis, tyrosine, mediates MDMA-induced 5-HT depletions. Extracellular tyrosine concentrations increased fivefold in striatum and 2.5-fold in hippocampus during the administration of neurotoxic doses of MDMA. In vitro results show that L-tyrosine can be hydroxylated nonenzymatically to the DA precursor l-3,4-dihydroxyphenylalanine (DOPA) under pro-oxidant conditions. The local infusion of L-tyrosine into the striatum or hippocampus during MDMA administration potentiated the acute increase in extracellular DA and the long-term depletion of 5-HT after MDMA. Coinfusion of the aromatic amino acid decarboxylase (AADC) inhibitor m-hydroxybenzylhydrazine attenuated these effects in hippocampus and decreased basal extracellular DA in the striatum. In contrast, the reverse dialysis of the tyrosine hydroxylase inhibitor alpha-methyl-p-tyrosine into the hippocampus did not affect MDMA-induced increases in extracellular DA or the long-term depletion in 5-HT. These results show that MDMA increases the concentration of tyrosine in the brain to cause a long-term depletion of 5-HT via the nonenzymatic, tyrosine hydroxylase-independent, hydroxylation of tyrosine to DOPA and subsequently to DA via AADC. Overall, the findings suggest that MDMA depletes 5-HT by increasing tyrosine and its eventual conversion to DA within 5-HT terminals.

Ecstasy: are animal data consistent between species and can they translate to humans?

The number of 3,4-methylenedioxymethamphetamine (ecstasy or MDMA) animal research articles is rapidly increasing and yet studies which place emphasis on the clinical significance are limited due to a lack of reliable human data. MDMA produces an acute, rapid release of brain serotonin and dopamine in experimental animals and in the rat this is associated with increased locomotor activity and the serotonin behavioural syndrome in rats. MDMA causes dose-dependent hyperthermia, which is potentially fatal, in humans, primates and rodents. Subsequent serotonergic neurotoxicity has been demonstrated by biochemical and histological studies and is reported to last for months in rats and years in non-human primates. Relating human data to findings in animals is complicated by reports that MDMA exposure in mice produces selective long-term dopaminergic impairment with no effect on serotonin. This review compares data obtained from animal and human studies and examines the acute physiological, behavioural and biochemical effects of MDMA as well as the long-term behavioural effects together with serotonergic and dopaminergic impairments. Consideration is also given to the role of neurotoxic metabolites and the influence of age, sex and user groups on the long-term actions of MDMA.

Synthesis of Fluoro Analogues of 3,4-(Methylenedioxy)amphetamine (MDA) and Its Derivatives

The role of the metabolism of the entactogen 3,4-(methylenedioxy)methamphetamine (MDMA; 1b) in neurotoxic or psychopharmacologic action is widely discussed, but not yet fully understood. To prompt further investigation into the role of MDMA metabolism, six new 3,4-(difluoromethylenedioxy) analogues of MDMA (1b) were prepared and characterized. Although electronically very different, the fluoro analogues 3-5 should be sterically very similar to the non-fluorinated parent compounds. The F-atoms may prevent the formation of toxic metabolites produced via a radical pathway (Scheme 1). Different theories regarding MDMA-induced neurotoxicity are briefly reviewed and discussed. The novel compounds 3-5 may help to verify the hypothesis that MDMA-induced neurotoxicity is the result of the formation of metabolites lacking the methylenedioxy bridge.

Pharmacokinetic profile of single and repeated oral doses of MDMA in squirrel monkeys: relationship to lasting effects on brain serotonin neurons

A large body of data indicates that (+/-)3,4-methylenedioxymethamphetamine (MDMA, 'ecstasy') can damage brain serotonin neurons in animals. However, the relevance of these preclinical data to humans is uncertain, because doses and routes of administration used in animals have generally differed from those used by humans. Here, we examined the pharmacokinetic profile of MDMA in squirrel monkeys after different routes of administration, and explored the relationship between acute plasma MDMA concentrations after repeated oral dosing and subsequent brain serotonin deficits. Oral MDMA administration engendered a plasma profile of MDMA in squirrel monkeys resembling that seen in humans, although the half-life of MDMA in monkeys is shorter (3 vs 6-9 h). MDMA was biotransformed into MDA, and the plasma ratio of MDA to MDMA was 3-5 / 100, similar to that in humans. MDMA accumulation in squirrel monkeys was nonlinear, and plasma levels were highly correlated with regional brain serotonin deficits observed 2 weeks later. The present results indicate that plasma concentrations of MDMA shown here to produce lasting serotonergic deficits in squirrel monkeys overlap those reported by other laboratories in some recreational 'ecstasy' consumers, and are two to three times higher than those found in humans administered a single 100-150 mg dose of MDMA in a controlled setting. Additional studies are needed on the relative sensitivity of brain serotonin neurons to MDMA toxicity in humans and non-human primates, the pharmacokinetic parameter(s) of MDMA most closely linked to the neurotoxic process, and metabolites other than MDA that may play a role.

Ecstasy-induced cell death in cortical neuronal cultures is serotonin 2A-receptor-dependent and potentiated under hyperthermia

Studies on 3,4-methylenedioxymethamphetamine ("ecstasy")-induced neurotoxicity mainly focus on damage of serotonergic terminals. Less attention has been given to neuronal cell death produced by 3,4-methylenedioxymethamphetamine and other amphetamines in areas including the cortex, striatum and thalamus. In the present study we investigated 3,4-methylenedioxymethamphetamine-induced neurotoxicity in neuronal serum free cultures from rat cortex. Since 3,4-methylenedioxymethamphetamine intake induces hyperthermia in both animals and humans, the experiments were performed under normal (36.5 degrees C) and hyperthermic conditions (40 degrees C). Our findings showed a dose-, time- and temperature-dependent apoptotic cell death induced by 3,4-methylenedioxymethamphetamine in cortical neurons. 3,4-Methylenedioxymethamphetamine-induced damage was potentiated under hyperthermia. The neurotoxicity was reduced by the serotonin 2A-receptor antagonists, ketanserin and (2R,4R)-5-[2-[2-[2-(3-methoxyphenyl)ethyl]phenoxy]ethyl]-1-methyl-3-pyrrolidinol hydrochloride, in both normothermic and hyperthermic conditions. (+/-)-2,5-Dimethoxy-4-iodoamphetamine hydrochloride, a model agonist for the serotonin 2A-receptor, also induced a dose- and time-dependent apoptotic cell death. Again, protection was provided by ketanserin and (2R,4R)-5-[2-[2-[2-(3-methoxyphenyl)ethyl]phenoxy]ethyl]-1-methyl-3-pyrrolidinol hydrochloride against (+/-)-2,5-dimethoxy-4-iodoamphetamine hydrochloride-induced neurotoxicity, thereby indicating that the 3,4-methylenedioxymethamphetamine stimulation of the serotonin 2A-receptor leads to neurotoxicity. This study provides for the first time evidence that direct 3,4-methylenedioxymethamphetamine serotonin 2A-receptor stimulation leads to neuronal cortical death. alpha-Phenyl-N-tert-butyl nitrone a free radical scavenger and the nitric oxide synthase inhibitor Nomega-nitro-L-arginine as well as the NMDA-receptor antagonist MK-801 provided protection under normothermia and hyperthermia, thereby suggesting the participation of free radicals in 3,4-methylenedioxymethamphetamine-induced cell death. Since 3,4-methylenedioxymethamphetamine serotonin 2A-receptor agonistic properties lead to neuronal death, clinically available atypical antipsychotic drugs with serotonin 2A-antagonistic properties could be a valuable therapeutic tool against 3,4-methylenedioxymethamphetamine-induced neurodegeneration.

Neurotoxicity of Ecstasy Metabolites in Rat Cortical Neurons, and Influence of Hyperthermia

3,4-Methylenedioxymethamphetamine (MDMA or "Ecstasy") is a widely abused, psychoactive recreational drug. There is growing evidence that the MDMA neurotoxic profile may be highly dependent on both its hepatic metabolism and body temperature. Metabolism of MDMA involves N-demethylation to 3,4-methylenedioxyamphetamine (MDA), which is also a drug of abuse. MDMA and MDA are O-demethylenated to N-methyl-alpha-methyldopamine (N-Me-alpha-MeDA) and alpha-methyldopamine (alpha-MeDA), respectively, both of which are catechols that can undergo oxidation to the corresponding ortho-quinones. In the presence of glutathione (GSH), ortho-quinones may be conjugated with GSH to form glutathionyl adducts. In this study, we evaluated the neurotoxicity of MDMA and three of its metabolites obtained by synthesis, N-Me-alpha-MeDA, alpha-MeDA, and 5-(GSH)-alpha-MeDA [5-(glutathion-S-yl)-alpha-methyldopamine] in rat cortical neuronal serum-free cultures under normal (36.5 degrees C) and hyperthermic (40 degrees C) conditions. Cell viability was assessed, and the mechanism of cell death was also evaluated. Our study shows that these metabolites are more neurotoxic [5-(GSH)-alpha-MeDA being the most toxic] than the parent compound MDMA. The neurotoxicity of MDMA metabolites was partially prevented by the antioxidants N-acetylcystein and also, in a minor extent, by alpha-phenyl-N-tert-butyl nitrone. All the tested compounds induced apoptotic cell death in cortical neurons, and their neurotoxic effect was potentiated under hyperthermic conditions. These data suggest that MDMA metabolites, especially under hyperthermic conditions, contribute to MDMA-induced neurotoxicity.

Neurotoxicity of MDMA (ecstasy): the limitations of scaling from animals to humans

Several studies suggest that MDMA-induced acute toxicity and long-term neurotoxicity is dependent on the metabolic disposition of MDMA. Differences in MDMA metabolism among animal species might therefore account for different sensitivities to its neurotoxic effects. The kinetic parameters of enzymes that regulate the formation of neurotoxic metabolites of MDMA differ among species, as does the ability of MDMA to self-inhibit these enzymes and the degree of genetic polymorphisms exhibited by these enzymes. Such features limit allometric scaling across animal models.

Human pharmacology of MDMA: pharmacokinetics, metabolism, and disposition

MDMA (3,4-methylenedioxymethamphetamine, ecstasy) is a widely misused psychostimulant drug abused among large segments of the young population. Pharmacologically it displays effects related to amphetamine-type drugs and a set of distinctive effects (closeness to others, facilitation to interpersonal relationship, and empathy) that have been named by some authors "entactogen" properties. MDMA is a potent releaser and/or reuptake inhibitor of presynaptic serotonin (5-HT), dopamine (DA), and norepinephrine (NE). These actions result from the interaction of MDMA with the membrane transporters involved in neurotransmitter reuptake and vesicular storage systems. The most frequent effects after MDMA/ecstasy administration are euphoria, well-being, happiness, stimulation, increased energy, extroversion, feeling close to others, increased empathy, increased sociability, enhanced mood, mild perceptual disturbances, changed perception of colors and sounds, somatic symptoms related to its cardiovascular and autonomic effects (blood pressure and heart rate increase, mydriasis), and moderate derealization but not hallucinations. Acute toxic effects are related to its pharmacologic actions. The serotonin syndrome (increased muscle rigidity, hyperreflexia, and hyperthermia), among others, is characteristic of acute toxicity episodes. MDMA metabolism is rather complex and includes 2 main metabolic pathways: (1) O-demethylenation followed by catechol-O-methyltransferase (COMT)-catalyzed methylation and/or glucuronide/sulfate conjugation; and (2) N-dealkylation, deamination, and oxidation to the corresponding benzoic acid derivatives conjugated with glycine. The fact that the polymorphic enzyme CYP2D6 partially regulates the O-demethylenation pathway prompted some expectations that subjects displaying the poor metabolizer phenotype may be at higher risk of acute toxicity episodes. In this metabolic pathway a mechanism-based inhibition of the enzyme operates because the formation of an enzyme-metabolite complex that renders all subjects, independently of genotype, phenotypically poor metabolizers after the administration of 2 consecutive doses. Therefore, the impact of CYP2D6 pharmacogenetics on acute toxicity is limited. One of the interesting features of MDMA metabolism is its potential involvement in the development of mid- to long-term neurotoxic effects as a result of progressive neurodegeneration of the serotonergic neurotransmission system.

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

RATIONALE AND OBJECTIVES

The majority of experimental and clinical studies on the pharmacology of 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) tend to focus on its action on 5-HT biochemistry and function. However, there is considerable evidence for MDMA having marked acute effects on dopamine release. Furthermore, while MDMA produces long-term effects on 5-HT neurones in most species examined, in mice its long-term effects appear to be restricted to the dopamine system. The objective of this review is to examine the actions of MDMA on dopamine biochemistry and function in mice, rats, guinea pigs, monkeys and humans.

RESULTS AND DISCUSSION

MDMA appears to produce a major release of dopamine from its nerve endings in all species investigated. This release plays a significant role in the expression of many of the behaviours that occur, including behavioural changes, alterations of the mental state in humans and the potentially life-threatening hyperthermia that can occur. While MDMA appears to be a selective 5-HT neurotoxin in most species examined (rats, guinea pigs and primates), it is a selective dopamine neurotoxin in mice. Selectivity may be a consequence of what neurotoxic metabolites are produced (which may depend on dosing schedules), their selectivity for monoamine nerve endings, or the endogenous free radical trapping ability of specific nerve endings, or both. We suggest more focus be made on the actions of MDMA on dopamine neurochemistry and function to provide a better understanding of the acute and long-term consequences of using this popular recreational drug.

The Role of Metabolism in 3,4-(±)-Methylenedioxyamphetamine and 3,4-(±)-Methylenedioxymethamphetamine (Ecstasy) toxicity

3,4-Methylenedioxyamphetamine (MDA) and 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) are ring-substituted amphetamine derivatives with stimulant and hallucinogenic properties. The recreational use of these amphetamines, especially MDMA, is prevalent despite warnings of irreversible damage to the central nervous system. MDA and MDMA are primarily serotonergic neurotoxicants. Because (1) neither MDA nor MDMA produces neurotoxicity when injected directly into brain, (2) intracerebroventricular (i.c.v.) administration of some major metabolites of MDA and MDMA fails to reproduce their neurotoxicity, (3) alpha-methyldopamine (alpha-MeDA) and N-methyl-alpha-MeDA are metabolites of both MDA and MDMA, (4) alpha-MeDA and N-methyl-alpha-MeDA are readily oxidized to the corresponding ortho-quinones, which can undergo conjugation with glutathione (GSH), and (5) quinone thioethers exhibit a variety of toxicologic activities, we initiated studies on the potential role of thioether metabolites of alpha-MeDA and N-methyl-alpha-MeDA in the neurotoxicity of MDA and MDMA. Our studies have revealed that the thioether conjugates stimulate the acute release of serotonin, dopamine, and norepinephrine and produce a behavioral response commensurate with the "serotonin syndrome." Direct injection of the conjugates into rat brain also produces long-term depletions in serotonin (5-HT) concentrations, elevations in GFAP expression, and activation of microglial cells. The data are consistent with the view that thioether metabolites of alpha-MeDA and N-methyl-alpha-MeDA contribute to the neurotoxicity of the parent amphetamines.

Serotonin neurotoxins--past and present

Autoxidation pathways and redox reactions of dihydroxytryptamines (5,6- and 5,7-DHT) and of 6-hydroxydopamine (6-OH-DA) are illustrated, and their potential role in aminergic neurotoxicity is discussed. It is proposed that certain aspects of the cytotoxicity of 6-OH-DA and of the DHTs, namely redox cycling of their quinone- and quinoneimine-intermediates as a source of free radicals, may also apply to quinoidal reactive intermediates and to glutathionyl- or cysteinyl conjugates ("thioether adducts") of o-dihydroxylated (catechol-like) metabolites of certain substituted amphetamines (of methylenedioxymethamphetamine (MDMA) and of methylenedioxyamphetamine (MDA)). Despite similarities in their primary interaction with the plasmalemmal (serotonergic transporter/dopamine transporter, SERT/DAT) and vesicular monoamine transporters (VMAT2), MDMA and fenfluramine (N-ethyl-meta-trifluoromethamphetamine, Fen) differ substantially in many aspects of their metabolism, pharmacokinetics, pharmacology, and neurotoxicology profile; the consequences of these differences for neuronal response patterns and long-term survival prospects are not yet fully understood. However, sustained hyperthermia appears to be a critical factor in these differences. Methodological requirements for adequate detection and description of pre- and postsynaptic forms of drug-induced neurotoxicity are exemplified using recently published accounts. The inclusion of microglial markers into research strategies has widened contemporary pathogenetic concepts on methamphetamine (MA)-induced neurotoxicity as an example of inflammatory neurodegeneration, thus complementing the traditional ROS and RNS-dependent stress models. Amphetamine-type neurotoxicity studies may assist in elaborating of preventive strategies for human neurodegenerative disorders.

Synthesis, in vitro formation, and behavioural effects of glutathione regioisomers of alpha-methyldopamine with relevance to MDA and MDMA (ecstasy)

Administration of 3,4-methylenedioxymethamphetamine (MDMA) or 3,4-methylenedioxyamphetamine (MDA) to rats produces serotonergic nerve terminal degeneration. However, they are not neurotoxic when injected directly into the brain, suggesting the requirement for peripheral metabolism of MDMA to a neurotoxic metabolite. Alpha-methyldopamine (alpha-MeDA) is a major metabolite of MDA. There are indications that a glutathione metabolite of alpha-MeDA and/or 3,4-dihydroxymethamphetamine may be responsible for the neurotoxicity and some of the behavioural effects produced by MDMA and/or MDA. The present study details the synthesis, purification and separation of the 5-(glutathion-S-yl)-alpha-MeDA and 6-(glutathion-S-yl)-alpha-MeDA regioisomers of alpha-MeDA. Incubation of MDA with human liver microsomes demonstrated that production of both glutathione adducts are related to cytochrome P450 2D6 isoform activity. Following intracerebroventricular administration (180 nmol) of either GSH adduct into Dark Agouti or Sprague-Dawley rats only 5-(glutathion-S-yl)-alpha-MeDA produced behavioural effects characterised by hyperactivity, teeth chattering, tremor/trembling, head weaving, splayed posture, clonus and wet dog shakes. Pre-treatment with a dopamine receptor antagonist (haloperidol, 0.25 mg/kg; i.p.) attenuated hyperactivity, teeth chattering, low posture and clonus and potentiated splayed postural effects. These results indicate that MDA can be converted into two glutathione regioisomers by human liver microsomes, but only the 5-(glutathion-S-yl)-alpha-MeDA adduct is behaviourally active in the rat.

Anticataleptic activity of cathinone and MDMA (Ecstasy) upon acute and subchronic administration in rat

It was recently demonstrated that acute administration of 3,4-methylenedioxymethamphet-amine (MDMA, "Ecstasy") is capable of counteracting haloperidol-induced catalepsy in rats. The present study was done with another psychostimulant, S-(-)-cathinone. In these experiments, 32 male Sprague-Dawley rats, 225 +/- 25 g, were used. They were divided into three groups. All groups received 0.5 mg/kg haloperidol in normal saline (s.c.) as a first injection. Then 30 min later each group received either isotonic phosphate-buffered saline, 1 mg/kg S-(-)-cathinone, or 2.5 mg/kg (RS)-MDMA (s.c.) as a second injection. The results of descent latency on both the horizontal bar and vertical grid showed that S-(-)-cathinone or (RS)-MDMA upon acute administration induces a strong anticataleptic activity (P < 0.0001) compared to rats treated with haloperidol plus vehicle. The effect of both drugs was later masked upon subchronic administration (days 2-7, 26-29). This is probably due to sensitization of cataleptic behavior. However, when the same groups of rats were tested on day 8 in a different task, i.e., open-field, they showed a significant difference (P < 0.05). The detailed mechanism of the observed strong anticataleptic activity of S-(-)-cathinone (which is considered a potent dopamine releaser) requires further investigation.

The pharmacology and clinical pharmacology of 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy")

The amphetamine derivative (+/-)-3,4-methylenedioxymethamphetamine (MDMA, ecstasy) is a popular recreational drug among young people, particularly those involved in the dance culture. MDMA produces an acute, rapid enhancement in the release of both serotonin (5-HT) and dopamine from nerve endings in the brains of experimental animals. It produces increased locomotor activity and the serotonin behavioral syndrome in rats. Crucially, it produces dose-dependent hyperthermia that is potentially fatal in rodents, primates, and humans. Some recovery of 5-HT stores can be seen within 24 h of MDMA administration. However, cerebral 5-HT concentrations then decline due to specific neurotoxic damage to 5-HT nerve endings in the forebrain. This neurodegeneration, which has been demonstrated both biochemically and histologically, lasts for months in rats and years in primates. In general, other neurotransmitters appear unaffected. In contrast, MDMA produces a selective long-term loss of dopamine nerve endings in mice. Studies on the mechanisms involved in the neurotoxicity in both rats and mice implicate the formation of tissue-damaging free radicals. Increased free radical formation may result from the further breakdown of MDMA metabolic products. Evidence for the occurrence of MDMA-induced neurotoxic damage in human users remains equivocal, although some biochemical and functional data suggest that damage may occur in the brains of heavy users. There is also some evidence for long-term physiological and psychological changes occurring in human recreational users. However, such evidence is complicated by the lack of knowledge of doses ingested and the fact that many subjects studied are or have been poly-drug users.

Plasma levels of parent compound and metabolites after doses of either d-fenfluramine or d-3,4-methylenedioxymethamphetamine (MDMA) that produce long-term serotonergic alterations

Plasma levels of parent compounds and metabolites were determined in adult rhesus monkeys after doses of either 5mg/kg d-fenfluramine (FEN) or 10mg/kg d-3, 4-methylenedioxymethamphetamine (MDMA) i.m. twice daily for four consecutive days. These treatment regimens have been previously shown to produce long-term serotonin (5-HT) depletions. Peak plasma levels of 2.0+/-0.4 microM FEN were reached within 40min after the first dose of FEN, and then declined rapidly, while peak plasma levels (0.4+/-0.1 microM) of the metabolite norfenfluramine (NFEN) were not reached until 6h after dosing. After the seventh (next to last) dose of FEN, peak plasma levels of FEN were 35% greater than after the first dose while peak NFEN-levels were 500% greater. The t(1/2) for FEN was 2.6+/-0.3h after the first dose and 3.2+/-0.2h after the seventh. The estimated t(1/2) for NFEN was more than 37.6+/-20.5h. Peak plasma levels of 9.5+/-2.5 microM MDMA were reached within 20min after the first dose of MDMA, and then declined rapidly, while peak plasma levels (0.9+/-0.2 microM) of the metabolite 3,4-methylenedioxyamphetamine (MDA) were not reached until 3-6h after dosing. After the seventh (next to last) dose of MDMA, peak plasma levels of MDMA were 30% greater than the first dose while peak MDA levels were elevated over 200%. The t(1/2) for MDMA was 2.8+/-0.4h after the first and 3.9+/-1.1h after the seventh dose. The estimated t(1/2) for MDA was about 8.3+/-1.0h. Variability in plasma levels of MDMA and MDA between subjects was much greater than that for FEN and NFEN. This variability in MDMA and MDA exposure levels may have lead to variability in the subsequent disruption of some behaviors seen in these same subjects. There were 80% reductions in the plasma membrane-associated 5-HT transporters 6 months after either the FEN or MDMA dosing regimen indicating that both treatments produced long-term serotonergic effects.

Altered states: the clinical effects of Ecstasy

Ecstasy is the second most widely abused illegal drug in Europe. Ecstasy is the colloquial name for 3,4-methylenedioxymethamphetamine (MDMA), but not all Ecstasy tablets contain MDMA. When taken in hot, crowded environments, Ecstasy/MDMA users have developed acute complications that have had fatal consequences. Epidemiological evidence indicates that adverse reactions to Ecstasy/MDMA intoxication are rare and idiosyncratic. Potential mechanisms of action are reviewed. In animal studies, MDMA damages serotonergic fibres and reduces the number of serotonin transporter sites within the CNS. Demonstration of neurotoxicity in human users of Ecstasy is hampered by a number of confounds that the majority of published studies have failed to address. These confounds are reviewed and their impact is discussed.

3,4-Methylenedioxymethamphetamine ("Ecstasy") induces apoptosis of cultured rat liver cells

"Ecstasy" (3,4-methylenedioxymethamphetamine, MDMA) has been shown to be hepatotoxic for human users, but molecular mechanisms involved in this effect remained poorly understood. MDMA-induced cell damage is related to programmed cell death in serotonergic and dopaminergic neurons. However, until now there has been no evidence of apoptosis induced by MDMA in liver cells. Here we demonstrate that exposure to MDMA caused apoptosis of freshly isolated rat hepatocytes and of a cell line of hepatic stellate cells (HSC), as shown by chromatin condensation of the nuclei and accumulation of oligonucleosomal fragments in the cytoplasm. In both cell types, apoptosis correlated with decreased levels of bcl-x(L), release of cytochrome c from the mitochondria and activation of caspase 3. In HSC, but not in hepatocytes, MDMA induced poly(ADP-ribose)polymerase (PARP) proteolysis. These results suggest that apoptosis of liver cells could be involved in the hepatotoxicity of MDMA.

Regional and cellular expression of CYP2D6 in human brain: higher levels in alcoholics

Cytochrome P450 (CYP) 2D6 is expressed in liver, brain and other extrahepatic tissues where it metabolizes a range of centrally acting drugs and toxins. As ethanol can induce CYP2D in rat brain, we hypothesized that CYP2D6 expression is higher in brains of human alcoholics. We examined regional and cellular expression of CYP2D6 mRNA and protein by RT-PCR, Southern blotting, slot blotting, immunoblotting and immunocytochemistry. A significant correlation was found between mean mRNA and CYP2D6 protein levels across 13 brain regions. Higher expression was detected in 13 brain regions of alcoholics (n = 8) compared to nonalcoholics (n = 5) (anovap < 0.0001). In hippocampus this was localized in CA1-3 pyramidal cells and dentate gyrus granular neurons. In cerebellum this was localized in Purkinje cells and their dendrites. Both of these brain regions, and these same cell-types, are known to be susceptible to alcohol damage. For one case, a poor metabolizer (CYP2D6*4/*4), there was no detectable CYP2D6 protein, confirming the specificity of the antibody used. These data suggest that in alcoholics elevated brain CYP2D6 expression may contribute to altered sensitivity to centrally acting drugs and to the mediation of neurotoxic and behavioral effects of alcohol.

High-performance liquid chromatography with electrochemical detection applied to the analysis of 3,4-dihydroxymethamphetamine in human plasma and urine

Metabolic activation in the disposition of 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy") has been implicated in some of its pharmacological and toxicological effects, with the major metabolite 3,4-dihydroxymethamphetamine (HHMA) as a putative toxicant through the formation of thioether adducts. We describe the first validated method for HHMA determination based on acid hydrolysis of plasma and urine samples, further extraction by a solid-phase strong cation-exchange resin (SCX, benzenesulfonic acid), and analysis of extracts by high-performance liquid chromatography with electrochemical detection. The chromatographic separation was performed in an n-butyl-silane (C4) column and the mobile phase was a mixture of 0.1 M sodium acetate containing 0.1 M 1-octanesulphonic acid and 4 mM EDTA (pH 3.1) and acetonitrile (82:18, v/v). Compounds were monitored with an electrochemical cell (working potentials 1 and 2, +0.05 and +0.35 V, respectively, gain 60 microA). A mobile phase conditioning cell with a potential set at +0.40 V was connected between the pumping system and the injector. Calibration curves were linear within the working concentration ranges of 50-1000 microg/L for urine and plasma. Limits of detection and quantification were 10.5 and 31.8 microg/L for urine and 9.2 and 28.2 microg/L for plasma. Recoveries for HHMA and DHBA (3,4-dihydroxybenzylamine, internal standard) were close to 50% for both biological matrices. Intermediate precision and inter-day accuracy were within 3.9-6.5% and 7.4-15.3% for urine and 5.0-10.8% and 9.2-13.4% for plasma.

Toxicokinetics of amphetamines: metabolism and toxicokinetic data of designer drugs, amphetamine, methamphetamine, and their N-alkyl derivatives

This paper reviews the toxicokinetics of amphetamines. The designer drugs MDA (methylenedioxy-amphetamine, R,S-1-(3;,4;-methylenedioxyphenyl)2-propanamine), MDMA (R,S-methylenedioxymethamphetamine), and MDE (R,S-methylenedioxyethylamphetamine), as well as BDB (benzodioxolylbutanamine; R,S-1-(1;,3;-benzodioxol-5;-yl)-2-butanamine or R,S-1-(3;,4;-methylenedioxyphenyl)-2-butanamine) and MBDB (R,S-N-methyl-benzodioxolylbutanamine), were taken into consideration, as were the following N-alkylated amphetamine derivatives: amphetaminil, benzphetamine, clobenzorex, dimethylamphetamine, ethylamphetamine, famprofazone, fencamine, fenethylline, fenproporex, furfenorex, mefenorex, mesocarb, methamphetamine, prenylamine, and selegiline. English-language publications from 1995 to 2000 were reviewed. Papers describing identification of metabolites or cytochrome P450 isoenzyme-dependent metabolism and papers containing pharmacokinetic/toxicokinetic data were considered and summarized. The implications of toxicokinetics for toxicologic assessment or for interpretation in forensic cases are discussed.

The effect of 3,4-methylenedioxymethamphetamine (MDMA, 'ecstasy') and its metabolites on neurohypophysial hormone release from the isolated rat hypothalamus

Methylenedioxymethamphetamine (MDMA, 'ecstasy'), widely used as a recreational drug, can produce hyponatraemia. The possibility that this could result from stimulation of vasopressin by MDMA or one of its metabolites has been investigated in vitro. Release of both oxytocin and vasopressin from isolated hypothalami obtained from male Wistar rats was determined under basal conditions and following potassium (40 mM) stimulation. The results were compared with those obtained for basal and stimulated release in the presence of MDMA or metabolites in the dose range 1 microM to 100 pM (n=5 - 8) using Student's t-test with Dunnett's correction for multiple comparisons. All compounds tested affected neurohypophysial hormone release, HMMA (4-hydroxy-3-methoxymethamphetamine) and DHA (3,4-dihydroxyamphetamine) being more active than MDMA, and DHMA (3,4-dihydroxymethamphetamine) being the least active. The effect on vasopressin release was greater than that on oxytocin. In the presence of HMMA the ratio test:control for basal release increased for vasopressin from 1.1+/-0.16 to 2.7+/-0.44 (s.e.m., P<0.05) at 10 nM and for oxytocin from 1.0+/-0.05 to 1.6+/-0.12 in the same hypothalami. For MDMA the ratio increased to 1.5+/-0.27 for vasopressin and to 1.28+/-0.04 for oxytocin for 10 nM. MDMA and its metabolites can stimulate both oxytocin and vasopressin release in vitro, the response being dose dependent for each drug with HMMA being the most potent.

In vitro neuronal and vascular responses to 5-HT in rats chronically exposed to MDMA

1. This study examined the effects of chronic exposure of rats to 3,4-methylenedioxymethamphetamine (MDMA) on [(3)H]5-hydroxytryptamine ([(3)H]5-HT) re-uptake into purified rat brain synaptosomes, 5-HT-induced isometric contraction of aortic rings and [(3)H]5-HT re-uptake into rat aorta. 2. Rats were administered MDMA (20 mg kg(-1) i.p.) twice daily over 4 days. One, 7, 14 or 21 days post treatment, whole brain synaptosomes and descending thoracic aortic rings were prepared for investigation. 3. Chronic MDMA treatment significantly reduced the maximum rate (V(max)) of specific high-affinity [(3)H]5-HT re-uptake 1 day after treatment and for up to 21 days post-final administration of MDMA. Direct application of MDMA (100 microM) abolished synaptosomal re-uptake of [(3)H]5-HT in vitro. 4. Chronic MDMA administration significantly reduced the maximum contraction (E(max)) to 5-HT at 1 and 7 days after treatment, but not at 14 or 21 days. 5. Chronic MDMA administration had no effect on sodium-dependent [(3)H]5-HT re-uptake into aorta 1 day after treatment, nor did 100 microM MDMA have any direct effect on [(3)H]5-HT uptake into aortic rings in vitro. 6. These results show, for the first time, an altered responsiveness of vascular tissue to MDMA after chronic administration. In addition, they demonstrate a difference in the sensitivity of central and peripheral 5-HT uptake systems to chronic MDMA exposure, and suggest that the action of MDMA in the cardiovascular system does not arise from a direct effect of MDMA on peripheral 5-HT transport.

Identification of the human cytochromes P450 involved in the oxidative metabolism of "Ecstasy"-related designer drugs

The human cytochrome P450 (CYP) isozymes catalyzing the oxidative metabolism of the widely abused amphetamine derivatives MDMA (N-methyl-3,4-methylenedioxyamphetamine, "Ecstasy"), MDE (N-ethyl-3, 4-methylenedioxyamphetamine, "Eve"), and MDA (3, 4-methylenedioxyamphetamine) were identified. Using a simplified non-extractive reversed-phase HPLC assay with fluorescence detection, biphasic Michaelis-Menten kinetics were obtained for formation of all three dihydroxyamphetamines in liver microsomes from a CYP2D6 extensive metabolizer subject. In contrast, no low K(m) component was detectable in microsomes from a poor metabolizer subject. Additional specific probes for CYP2D6 further confirmed this isozyme as the exclusive low K(m) component for demethylenation. P450-selective inhibitors applied to CYP2D6-inhibited microsomes and activity measurements in a series of recombinant P450s suggested CYP1A2 as the major high K(m) component with contributions by CYP2B6 and CYP3A4. Moreover, the relative CYP1A2 content of a panel of 12 human livers was weakly but significantly correlated to the high K(m) demethylenase activity (Spearman rank correlation coefficient [r(s)] = 0.58; P < 0.05). Microsomal maximal velocities for N-dealkylation were at least 7-fold lower than for demethylenation and were characterized by apparently monophasic kinetics. The most important isozyme for this reaction appeared to be CYP2B6, the microsomal content of which was found to be strongly correlated to N-deethylation of MDE (r(s) = 0.90; P < 0.001). We conclude that, in addition to CP2D6 as the sole high-affinity demethylenase, several other P450 isozymes have the capacity to contribute to microsomal oxidative metabolism of methylenedioxyamphetamines. This may be of particular importance in individuals genetically lacking functional CYP2D6.

Toxicokinetics and analytical toxicology of amphetamine-derived designer drugs ('Ecstasy')

The phase I and II metabolites of the designer drugs methylenedioxyamphetamine (MDA), R,S-methylenedioxymethamphetamine (MDMA), R,S-methylenedioxyethylamphetamine (MDE), R, S-benzodioxazolylbutanamine (BDB) and R, S-N-methyl-benzodioxazolylbutanamine (MBDB) were identified by gas chromatography-mass spectrometry (GC-MS) or liquid chromotography-mass spectrometry (LC-MS) in urine and liver microsomes of humans and rats. Two overlapping pathways could be postulated: (1) demethylenation followed by catechol-O-methyl-transferase (COMT) catalyzed methylation and/or glucuronidation/sulfatation; (2) N-dealkylation, deamination and only for MDA, MDMA, MDE oxidation to the corresponding benzoic acid derivatives conjugated with glycine. Demethylenation was mainly catalyzed by CYP2D1/6 or CYP3A2/4, but also by CYP independent mechanisms. In humans, MDMA and MBDB could also be demethylenated by CYP1A2. N-demethylation was mainly catalyzed by CYP1A2, N-deethylation by CYP3A2/4. Based on these studies, GC-MS procedures were developed for the toxicological analysis in urine and plasma. Finally, toxicokinetic parameters are reviewed.

An assessment of the acute effects of the serotonin releasers methylenedioxymethamphetamine, methylenedioxyamphetamine and fenfluramine on immunity in rats

The purpose of the present study was to examine the effect of the serotonin releasing amphetamine derivatives methylenedioxymethamphetamine (MDMA), methylenedioxyamphetamine (MDA) and fenfluramine (FEN) on immunity in rats. Similar to MDA and MDMA, FEN reduced the number of circulating lymphocytes, provoked a suppression of Con A-stimulated lymphocyte proliferation and total IFN-gamma and IL-10 production in diluted whole blood cultures. Thus the non-psychostimulant amphetamine derivative FEN, shares the ability of the psychostimulant methylenedioxy-substituted amphetamine derivatives to alter these indices of immune function in the rat. However, when Con A-stimulated cytokine production was normalised for the number of lymphocytes in culture in order to examine cytokine production at a cellular level, the effect of the amphetamine derivatives begins to diverge. FEN shares with MDMA and MDA the ability to suppress production of the Th2 type cytokine IL-10. However the effect of these drugs on Th1 type cytokine secretion was much more complex. While the methylendioxy-substituted amphetamines increases the secretion of the Th1 type cytokine IL-2 without altering the related Th1 type cytokine IFN-gamma, FEN did not alter IL-2 secretion, but suppressed IFN-gamma secretion. In addition to these effects on T-cell responses, all three drugs inhibited LPS-induced TNF-alpha secretion from diluted whole blood cultures suggesting that macrophage activity is impaired following treatment. In all, these data extend our previous findings concerning the effects of MDMA on the immune system and demonstrate that the related serotonin releasers MDA and FEN also provoke immunological changes in rats.

Acute toxicity of 3,4-methylenedioxymethamphetamine (MDMA) in Sprague-Dawley and Dark Agouti rats

Ingestion of MDMA ("ecstasy") by humans can cause acute toxicity manifested by hyperthermia and death. Demethylenation of MDMA is catalyzed by cytochrome P-450 2D6 (CYP2D6) and cytochrome P-450 2D1 (CYP2D1) in humans and rats, respectively, and is polymorphically expressed. It has been proposed that CYP2D6 deficiency may account for the unexplained toxicity of MDMA. The female Dark Agouti rat is deficient in CYP2D1, and serves as a model for the human poor metabolizer. We investigated thermogenic and locomotor actions of MDMA in adult female Sprague-Dawley (CYP2D1 replete) and Dark Agouti rats. MDMA (2, 5, and 10 mg/kg) and saline were injected subcutaneously at ambient temperatures of 22 and 31 degrees C. There was no difference in core temperature responses between the two rat strains. Hypothermia occurred in the first 30 min and temperature elevation thereafter. MDMA increased locomotor activity in Sprague-Dawley but not in Dark Agouti rats. However, MDMA had pronounced lethal effects at 31 degrees C ambient in the Dark Agouti rats only. We conclude that the poor metaboliser phenotype may predispose to lethality, but the mechanism is as yet unknown.