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

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

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

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

Synthesis and Cytotoxic Profile of 3,4-Methylenedioxymethamphetamine (“Ecstasy”) and Its Metabolites on Undifferentiated PC12 Cells: A Putative Structure−Toxicity Relationship

The toxicological and redox profiles of MDMA and its major metabolites (MDA, alpha-methyldopamine, N-methyl-alpha-methyldopamine, 6-hydroxy-alpha-methyldopamine, 3-methoxy-alpha-methyldopamine) were studied to establish a structure-toxicity relationship and determine their individual contribution to cell death induction by apoptosis and/or necrosis. The results of the comparative toxicity study, using undifferentiated PC12 cells, strongly suggest that the metabolites possessing a catecholic group are more toxic to the cells than MDMA and metabolites with at least one protected phenolic group. Redox studies reveal that an oxidative mechanism seems to play an important role in metabolite cytotoxicity. Nuclear features of apoptosis and/or necrosis show that most of the metabolites, particularly N-methyl-alpha-methyldopamine, induce cell death by apoptosis, largely accompanied by necrotic features. No significant differences were found between MDMA and the metabolites, concerning overall characteristics of cell death. These results may be useful to ascertain the contribution of metabolism in MDMA neurotoxicity molecular mechanisms.

Caffeine promotes hyperthermia and serotonergic loss following co-administration of the substituted amphetamines, MDMA (“Ecstasy”) and MDA (“Love”)

The present study determined the effect of caffeine co-administration on the core body temperature response and long-term serotonin (5-HT) loss induced by methylenedioxymethamphetamine (MDMA; "Ecstasy") and its metabolite methylenedioxyamphetamine (MDA; "Love") to rats. In group-housed animals, caffeine (10 mg/kg) enhanced the acute toxicity of MDMA (15 mg/kg) and MDA (7.5 mg/kg), resulting in an exaggerated hyperthermic response (+2 degrees C for 5 h following MDMA and +1.5 degrees C for 3 h following MDA) when compared to MDMA (+1 degree C for 3 h) and MDA (+1 degree C for 1 h) alone. Co-administration of caffeine with MDMA or MDA was also associated with increased lethality. To reduce the risk of lethality, doses of MDMA and MDA were reduced in further experiments and the animals were housed individually. To examine the effects of repeated administration, animals received MDMA (10 mg/kg) or MDA (5 mg/kg) with or without caffeine (10 mg/kg) twice daily for 4 consecutive days. MDMA and MDA alone induced hypothermia (fall of 1 to 2 degrees C) over the 4 treatment days. Co-administration of caffeine with MDMA or MDA resulted in hyperthermia (increase of up to 2.5 degrees C) following acute administration compared to animals treated with caffeine or MDMA/MDA alone. This hyperthermic response to caffeine and MDMA was not observed with repeated administration, unlike caffeine + MDA, where hyperthermia was obtained over the 4 day treatment period. In addition, 4 weeks after the last treatment, co-administration of caffeine with MDA (but not MDMA) induced a reduction in 5-HT and 5-hydroxyindole acetic acid (5-HIAA) concentrations in frontal cortex (to 61% and 58% of control, respectively), hippocampus (48% and 60%), striatum (79% and 64%) and amygdala (63% and 37%). However, when caffeine (10 mg/kg) and MDMA (2.5 mg/kg) were co-administered four times daily for 2 days to group-housed animals, both hyperthermia and hippocampal 5-HT loss were observed (reduced to 68% of control). Neither MDMA nor MDA alone induced a significant reduction in regional 5-HT or 5-HIAA concentrations following repeated administration. In conclusion, caffeine promotes the acute and long-term toxicity associated with MDMA and MDA. This is a serious drug interaction, which could have important acute and long-term health consequences for recreational drug users.

Amphetamine toxicity in the emergency department

XTC and other amphetamines are considered to be safe by the majority of partying young people who are unaware of (or unwilling to know about) the acute and chronic toxicity of these substances, and these drugs are widespread, illicit stimulants. In this article, we describe four cases of severe acute toxicity due to recreational use of amphetamines 3,4-methylene-dioxymethamphetamine, 3,4-methylenedioxyethylamphetamine, 3,4-methylenedioxyamphetamine, 4-methylthioamphetamine or p-methoxyamphetamine, with emphasis on the presenting symptoms and acute treatment in the emergency department.

Metabolism is required for the expression of ecstasy-induced cardiotoxicity in vitro

Cardiovascular complications associated with 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) abuse have increasingly been reported. The indirect effect of MDMA mediated by a sustained high level of circulating biogenic amines may contribute to the cardiotoxic effects, but other factors, like the direct toxic effects of MDMA and its metabolites in cardiac cells, remain to be investigated. Thus, the objective of the present in vitro study was to evaluate the potential cardiotoxic effects of MDMA and its major metabolites 3,4-methylenedioxyamphetamine (MDA), N-methyl-alpha-methyldopamine (N-Me-alpha-MeDA), and alpha-methyldopamine (alpha-MeDA) using freshly isolated adult rat cardiomyocytes. The cell suspensions were incubated with these compounds in the final concentrations of 0.1, 0.2, 0.4, 0.8, and 1.6 mM for 4 h. alpha-MeDA, N-Me-alpha-MeDA, and their respective aminochromes (oxidation products) were quantified in cell suspensions by HPLC-DAD. The toxic effects were evaluated at hourly intervals for 4 h by measuring the percentage of cells with normal morphology, glutathione (GSH), and glutathione disulfide (GSSG); intracellular Ca(2+), ATP, and ADP; and the cellular activities of glutathione peroxidase, glutathione reductase, and glutathione-S-transferase. No toxic effects were found after exposure of rat cardiomyocytes to MDMA or MDA at any of the tested concentrations for 4 h. In contrast, their catechol metabolites N-Me-alpha-MeDA and alpha-MeDA induced significant toxicity in rat cardiomyocytes. The toxic effects were characterized by a loss of normal cell morphology, which was preceded by a loss of GSH homeostasis due to conjugation of GSH with N-Me-alpha-MeDA and alpha-MeDA, sustained increase of intracellular Ca(2+) levels, ATP depletion, and decreases in the antioxidant enzyme activities. The oxidation of N-Me-alpha-MeDA and alpha-MeDA into the toxic compounds N-methyl-alpha-methyldopaminochrome and alpha-methyldopaminochrome, respectively, was also verified in cell suspensions incubated with these MDMA metabolites. The results obtained in this study provide evidence that the metabolism of MDMA into N-Me-alpha-MeDA and alpha-MeDA is required for the expression of MDMA-induced cardiotoxicity in vitro, being N-Me-alpha-MeDA the most toxic of the studied metabolites.

Prenatal 3,4-methylenedioxymethamphetamine (ecstasy) exposure induces long-term alterations in the dopaminergic and serotonergic functions in the rat

We investigated several aspects of the dopaminergic and serotonergic functions throughout brain development in rats prenatally exposed to MDMA ("ecstasy"). Pregnant rats were treated with MDMA (10 mg/kg s.c.) or saline from the 13th to the 20th day of gestation and studies were conducted on the progeny from both groups: (i) quantification of whole brain contents of DA, 5-HT and metabolites from the 14th day of embryonic life (E14) to weaning (21st day of postnatal life, P21); (ii) quantification of DA and 5-HT membrane transporters by autoradiography from E18 to adult age (P70); (iii) measurement of pharmacologically induced release of DA and 5-HT using microdialysis on adult (P70) freely moving rats; (iv) measurement of sucrose preference in adults (P70). Prenatally MDMA-exposed rats showed (i) a two-fold decrease of whole brain levels of 5-HT and 5-HIAA at P0; (ii) no effect on the DAT and SERT density; (iii) a strongly reduced pharmacologically induced release of DA and 5-HT at P70 in the striatum and hippocampus; and (iv) a significant 20% decrease in sucrose preference at P70. This study suggests that a prenatal exposure to MDMA induces transient and long-term neurochemical and behavioural modifications in dopaminergic and serotonergic functions.

Identification and characterization of metallothionein-1 and -2 gene expression in the context of (+/-)3,4-methylenedioxymethamphetamine-induced toxicity to brain dopaminergic neurons

In mice, the recreational drug (+/-)3,4-methylenedioxymethamphetamine [MDMA ("ecstasy")] produces a selective toxic effect on brain dopamine (DA) neurons. Using cDNA microarray technology in combination with an approach designed to facilitate recognition of relevant changes in gene expression, the present studies sought to identify genes potentially involved in murine MDMA-induced toxicity to DA neurons. Of 15,000 mouse cDNA fragments studied, metallothionein (Mt)-1 and Mt2 emerged as candidate genes possibly involved in MDMA-induced toxicity to DA neurons. Northern blot analysis confirmed the microarray findings and revealed a dynamic upregulation of Mt1 and Mt2 mRNA in the ventral midbrain within 4-12 hr after MDMA treatment. Western blot analysis showed a similar increase in MT protein levels, with peak times occurring subsequent to increases in mRNA levels. Mt1-2 double knock-out mice were more vulnerable to MDMA-induced toxicity to DA neurons than corresponding wild-type mice. Stimulation of endogenous expression of MT protein with zinc acetate conferred complete protection against MDMA-induced toxicity to DA neurons, and administration of exogenous MT protein afforded partial protection. Collectively, these results indicate that MDMA-induced toxicity to DA neurons is associated with increased Mt1 and Mt2 gene transcription and translation, possibly as part of a neuroprotective mechanism. The present findings may have therapeutic implications for neuropathological conditions involving DA neurons.

Rat brain serotonin neurones that express neuronal nitric oxide synthase have increased sensitivity to the substituted amphetamine serotonin toxins 3,4-methylenedioxymethamphetamine and p-chloroamphetamine

Substituted amphetamines such as p-chloroamphetamine and the abused drug methylenedioxymethamphetamine cause selective destruction of serotonin axons in rats, by unknown mechanisms. Since some serotonin neurones also express neuronal nitric oxide synthase, which has been implicated in neurotoxicity, the present study was undertaken to determine whether nitric oxide synthase expressing serotonin neurones are selectively vulnerable to methylenedioxymethamphetamine or p-chloroamphetamine. Using double-labeling immunocytochemistry and double in situ hybridization for nitric oxide synthase and the serotonin transporter, it was confirmed that about two thirds of serotonergic cell bodies in the dorsal raphé nucleus expressed nitric oxide synthase, however few if any serotonin transporter immunoreactive axons in striatum expressed nitric oxide synthase at detectable levels. Methylenedioxymethamphetamine (30 mg/kg) or p-chloroamphetamine (2 x 10 mg/kg) was administered to Sprague-Dawley rats, and 7 days after drug administration there were modest decreases in the levels of serotonin transporter protein in frontal cortex, and striatum using Western blotting, even though axonal loss could be clearly seen by immunostaining. p-Chloroamphetamine or methylenedioxymethamphetamine administration did not alter the level of nitric oxide synthase in striatum or frontal cortex, determined by Western blotting. Analysis of serotonin neuronal cell bodies 7 days after p-chloroamphetamine treatment, revealed a net down-regulation of serotonin transporter mRNA levels, and a profound change in expression of nitric oxide synthase, with 33% of serotonin transporter mRNA positive cells containing nitric oxide synthase mRNA, compared with 65% in control animals. Altogether these results support the hypothesis that serotonin neurones which express nitric oxide synthase are most vulnerable to substituted amphetamine toxicity, supporting the concept that the selective vulnerability of serotonin neurones has a molecular basis.

The Neuropsychopharmacology and Toxicology of 3,4-methylenedioxy-N-ethyl-amphetamine (MDEA)

This paper reviews the pharmacology and toxicology of 3,4-methylenedioxy-N-ethylamphetamine (MDEA, "eve"). MDEA is a ring-substituted amphetamine (RSA) like MDMA, its well known N-methyl analog. Both have become very popular substances of abuse in the techno- and house-music scene. They can evoke psychomotor stimulation, mild alterations of perception, sensations of closeness and a positive emotional state as well as sympathomimetic physical effects. At present, the name "ecstasy" is no longer used only for MDMA, but for the whole group of RSAs (MDA, MDMA, MDEA and MBDB) as they are chemically and pharmacologically nearly identical; moreover, many ecstasy pills contain mixtures of the RSAs. Hence, for a selective review on MDEA, it is crucial to strictly differentiate between: 1) street and chemical names, and 2) studies with or without chemically defined substances. In order to present MDEA-specific information, the pharmacodynamics and kinetics are described on the basis of MDEA challenge studies in animals and humans. In the toxicology section, we present a collection of case reports on fatalities where MDEA was toxicologically confirmed. On the question of serotonergic neurotoxicity and possible long-term consequences, however, MDEA-specific information is available from animal studies only. The neurotoxic potential of MDEA in humans is difficult to estimate, as ecstasy users do not consume pure substances. For future research, challenge studies in animals using dosing regimens adapted to human consumption patterns are needed. Such challenge studies should directly compare individual RSAs. They will represent the most viable and fruitful approach to the resolution of the highly controversial issues of serotonergic neurotoxicity and its functional consequences.

Hepatotoxicity of 3,4-methylenedioxyamphetamine and ?-methyldopamine in isolated rat hepatocytes: formation of glutathione conjugates

The amphetamine designer drugs 3,4-methylenedioxymethamphetamine (MDMA or "ecstasy") and its N-demethylated analogue 3,4-methylenedioxyamphetamine (MDA or "love") have been extensively used as recreational drugs of abuse. MDA itself is a main MDMA metabolite. MDMA abuse in humans has been associated with numerous reports of hepatocellular damage. Although MDMA undergoes extensive hepatic metabolism, the role of metabolites in MDMA-induced hepatotoxicity remains unclear. Thus, the aim of the present study was to evaluate the effects of MDA and alpha-methyldopamine (alpha-MeDA), a major metabolite of MDA, in freshly isolated rat hepatocyte suspensions. The cells were incubated with MDA or alpha-MeDA at final concentrations of 0.1, 0.2, 0.4, 0.8, or 1.6 mM for 3 h. The toxic effects induced following incubation of hepatocyte suspensions with these metabolites were evaluated by measuring cell viability, the extent of lipid peroxidation, levels of glutathione (GSH) and glutathione disulfide (GSSG), the formation of GSH conjugates, and the activities of GSSG reductase (GR), GSH peroxidase (GPX), and GSH S-transferase (GST). MDA induced a concentration- and time-dependent GSH depletion, but had a negligible effect on lipid peroxidation, cell viability, or on the activities of GR, GPX, and GST. In contrast, alpha-MeDA (1.6 mM, 3 h) induced a marked depletion of GSH accompanied by a loss on cell viability, and decreases in GR, GPX and GST activities, although no significant effect on lipid peroxidation was found. For both metabolites, GSH depletion was not accompanied by increases in GSSG levels; rather, 2-(glutathion- S-yl)-alpha-MeDA and 5-(glutathion- S-yl)-alpha-MeDA were identified by HPLC-DAD/EC within cells incubated with MDA or alpha-MeDA. The results provide evidence that one of the early consequences of MDMA metabolism is a disruption of thiol homeostasis, which may result in loss of protein function and the initiation of a cascade of events leading to cellular damage.

P-glycoprotein modulation by the designer drugs methylenedioxymethamphetamine, methylenedioxyethylamphetamine and paramethoxyamphetamine

There are increasing numbers of deaths related to taking MDMA, MDE and PMA reported where the deceased typically took several different drugs with these compounds. Hence, mutual modulation of the pharmacokinetics in drug combinations with "ecstasy" might be a risk factor for "ecstasy"-related morbidity. Regarding potential drug - drug interactions, there are no data evaluating a possible contribution of the multidrug resistance transporter P-glycoprotein (Pgp) in contrast to the cytochrome P450 enzyme system. Therefore, individual "ecstasy" compounds have been tested for their ability to interact with Pgp using a fluorometric calcein assay as a model for Pgp inhibition in porcine kidney epithelial cells with overexpression of human Pgp (L-MDR1). All three compounds increased calcein retention in L-MDR1 cells in a concentration-dependent manner, with MDE being the most potent and MDMA the weakest Pgp inhibitor. The effective concentrations were 1 - 3 orders of magnitude higher than plasma concentrations observed in vivo, suggesting that these compounds are only weak inhibitors of Pgp, which is unlikely to influence the access of other compounds to the brain. However, it cannot be excluded that co-administration of Pgp inhibitors such as ritonavir or paroxetine could increase MDMA, MDE and PMA bioavailability and also enhance brain entry leading to severe side effects.

Prenatal 3,4-methylenedioxymethamphetamine (ecstasy) alters exploratory behavior, reduces monoamine metabolism, and increases forebrain tyrosine hydroxylase fiber density of juvenile rats

3,4-Methylenedioxymethamphetamine (MDMA; ecstasy) use has risen among women of childbearing age. Consequently, there is a substantial risk for fetal exposure from women who are, or become pregnant while abusing MDMA. However, attempts to demonstrate that prenatal MDMA results in neurochemical alterations in rat models have failed. MDMA administration to neonatal rats (third trimester equivalent) results in significant and persistent neurochemical and behavioral alterations, yet human epidemiologic data suggest that the vast majority of prenatal exposure is limited to the first trimester. The following study was conducted to reexamine the potential for prenatal MDMA administration to produce lasting postnatal neurochemical and behavioral alterations using a new rodent model. Pregnant rats were administered twice-daily injections of MDMA (15 mg/kg sc) or saline from embryonic days (E) 14-20. Prenatally exposed pups were examined on postnatal days (P) 3 and 21. At P3, MDMA offspring showed reductions in the dopamine metabolite homovanillic acid which persisted through P21, along with reductions in the serotonin (5-HT) metabolite, 5-HIAA. Prenatally exposed MDMA animals at P21 also had reduced dopamine and 5-HT turnover in the nucleus accumbens. Increases in tyrosine hydroxylase fiber density were found in the frontal cortex, striatum and nucleus accumbens of MDMA animals. In addition, prenatal MDMA significantly increased locomotor activity of P21 pups in a 20-min novel cage environment. These findings provide the first evidence of lasting neurochemical and behavioral alterations following prenatal MDMA. Further investigation is warranted to elucidate possible mechanisms of action and to monitor children gestationally exposed to MDMA.

Synthesis and neurotoxicological evaluation of putative metabolites of the serotonergic neurotoxin 2-(methylamino)-1-[3,4-(methylenedioxy)phenyl]propane [(methylenedioxy)methamphetamine]

Theoretical considerations and recent experimental data have prompted an investigation of the neurotoxicological properties of the 6-hydroxydopamine analogue 2-(methylamino)-1-(2,4,5-trihydroxyphenyl)propane (5) and its possible precursor 1-[2-hydroxy-4,5-(methylenedioxy)phenyl]-2- (methylamino)propane (4), potential metabolites of the serotonergic neurotoxin MDMA. Systemic, intracerebroventricular, and intraparenchymal (intrastriatal and intracortical) administration of 4 led to no detectable alterations of hippocampal or cortical serotonin or striatal dopamine levels in the rat under conditions that caused significant biogenic amine depletions by established neurotoxins. By contrast, intraparenchymal administration of 5 caused profound depletions of dopamine and serotonin, with the former being more severely depleted than the latter. Although not conclusive, these data suggest a possible role for 5 in the mediation of MDMA's neurotoxic actions.

The pharmacology of the acute hyperthermic response that follows administration of 3,4-methylenedioxymethamphetamine (MDMA, 'ecstasy') to rats

1. The pharmacology of the acute hyperthermia that follows 3,4-methylenedioxymethamphetamine (MDMA, 'ecstasy') administration to rats has been investigated. 2. MDMA (12.5 mg kg(-1) i.p.) produced acute hyperthermia (measured rectally). The tail skin temperature did not increase, suggesting that MDMA may impair heat dissipation. 3. Pretreatment with the 5-HT(1/2) antagonist methysergide (10 mg kg(-1)), the 5-HT(2A) antagonist MDL 100,907 (0.1 mg kg(-1)) or the 5-HT(2C) antagonist SB 242084 (3 mg kg(-1)) failed to alter the hyperthermia. The 5-HT(2) antagonist ritanserin (1 mg kg(-1)) was without effect, but MDL 11,939 (5 mg kg(-1)) blocked the hyperthermia, possibly because of activity at non-serotonergic receptors. 4. The 5-HT uptake inhibitor zimeldine (10 mg kg(-1)) had no effect on MDMA-induced hyperthermia. The uptake inhibitor fluoxetine (10 mg kg(-1)) markedly attenuated the MDMA-induced increase in hippocampal extracellular 5-HT, also without altering hyperthermia. 5. The dopamine D(2) antagonist remoxipride (10 mg kg(-1)) did not alter MDMA-induced hyperthermia, but the D(1) antagonist SCH 23390 (0.3 - 2.0 mg kg(-1)) dose-dependently antagonized it. 6. The dopamine uptake inhibitor GBR 12909 (10 mg kg(-1)) did not alter the hyperthermic response and microdialysis demonstrated that it did not inhibit MDMA-induced striatal dopamine release. 7. These results demonstrate that in vivo MDMA-induced 5-HT release is inhibited by 5-HT uptake inhibitors, but MDMA-induced dopamine release may not be altered by a dopamine uptake inhibitor. 8. It is suggested that MDMA-induced hyperthermia results not from MDMA-induced 5-HT release, but rather from the increased release of dopamine that acts at D(1) receptors. This has implications for the clinical treatment of MDMA-induced hyperthermia.

Serotonergic neurotoxicity of 3,4-(+/-)-methylenedioxyamphetamine and 3,4-(+/-)-methylendioxymethamphetamine (ecstasy) is potentiated by inhibition of gamma-glutamyl transpeptidase

Reactive metabolites play an important role in 3,4-(+/-)-methylenedioxyamphetamine (MDA) and 3,4-(+/-)-methylenedioxymethamphetamine (MDMA; ecstasy)-mediated serotonergic neurotoxicity, although the specific identity of such metabolites remains unclear. 5-(Glutathion-S-yl)-alpha-methyldopamine (5-GSyl-alpha-MeDA) is a serotonergic neurotoxicant found in the bile of MDA-treated rats. The brain uptake of 5-GSyl-alpha-MeDA is decreased by glutathione (GSH), but sharply increases in animals pretreated with acivicin, an inhibitor of gamma-glutamyl transpeptidase (gamma-GT) suggesting competition between intact 5-GSyl-alpha-MeDA and GSH for the putative GSH transporter. gamma-GT is enriched in blood-brain barrier endothelial cells and is the only enzyme known to cleave the gamma-glutamyl bond of GSH. We now show that pretreatment of rats with acivicin (18 mg/kg, ip) inhibits brain microvessel endothelial gamma-GT activity by 60%, and potentiates MDA- and MDMA-mediated depletions in serotonin (5-HT) and 5-hydroxylindole acidic acid (5-HIAA) concentrations in brain regions enriched in 5-HT nerve terminal axons (striatum, cortex, hippocampus, and hypothalamus). In addition, glial fibrillary acidic protein (GFAP) expression increases in the striatum of acivicin and MDA (10 mg/kg) treated rats, but remains unchanged in animals treated with just MDA (10 mg/kg). Inhibition of endothelial cell gamma-GT at the blood-brain barrier likely enhances the uptake into brain of thioether metabolites of MDA and MDMA, such as 5-(glutathion-S-yl)-alpha-MeDA and 2,5-bis-(glutathion-S-yl)-alpha-MeDA, by increasing the pool of thioether conjugates available for uptake via the intact GSH transporter. The data indicate that thioether metabolites of MDA and MDMA contribute to the serotonergic neurotoxicity observed following peripheral administration of these drugs.

Behavioural, hyperthermic and neurotoxic effects of 3,4-methylenedioxymethamphetamine analogues in the Wistar rat

1. The ability of N-ethyl (MDEA) and N-butyl (MDBA) analogues of 3,4-methylenedioxymethamphetamine (MDMA, 'Ecstasy') to induce acute behavioural changes and increases in body temperature, and to cause serotonergic neurotoxicity, was assessed in young adult male Wistar rats. The in vitro ability of MDMA analogues to evoke presynaptic monoamine release from crude rat forebrain synaptosomal preparations pre-labelled with [3H]5-HT or [3H]DA was also measured. 2. In behavioural experiments, acute MDMA and MDEA (20 mg/kg, i.p.) significantly increased rat open-field locomotion scores, decreased open-field rearing, and induced stereotypy, Straub tail and head weaving. MDBA did not produce any of these behaviours. 3. After repeated dosing (8 x 20 mg/kg, i.p., twice daily for 4 days), MDMA > MDEA >> MDBA > or = saline at decreasing forebrain [3H]paroxetine binding levels and concentrations of 5-HT and 5-HIAA at 14 days post-treatment. None of the analogues caused any long-term changes in dopamine or noradrenaline concentrations in the forebrain. 4. Acute MDMA and MDEA (20 mg/kg, i.p.) produced significant acute increases in rat aural temperature compared with saline-treated animals, while 20 mg/kg MDBA caused no significant effects. 5. MDA, MDMA and MDEA were equipotent at inducing [3H]5-HT release from frontal cortex/hippocampal synaptosomes, while MDBA only evoked a significant release at 100 microM concentrations. The potency order for inducing [3H]DA release from striatal synaptosomes was MDA > MDMA > MDEA = MDBA. 6. This study shows that large N-alkyl substitution decreases the ability of MDMA analogues to evoke presynaptic 5-HT and DA release, induce acute hyperthermia, hyperlocomotion and behavioural changes, and cause long-term serotonergic neurotoxicity. 7. The structure-activity relationship data presented here indicate that the neurotoxic damage caused by substituted amphetamines requires a combination of acute hyperthermia and increased neurotransmitter release. Induction of one of these effects in isolation is not sufficient to cause serotonergic nerve terminal degradation.

Glutathione and N-acetylcysteine conjugates of alpha-methyldopamine produce serotonergic neurotoxicity: possible role in methylenedioxyamphetamine-mediated neurotoxicity

Direct injection of either 3,4-(+/-)-methylenedioxymethamphetamine (MDMA) or 3,4-(+/-)-methylenedioxyamphetamine (MDA) into the brain fails to reproduce the serotonergic neurotoxicity seen following peripheral administration. The serotonergic neurotoxicity of MDA and MDMA therefore appears to be dependent upon the generation of a neurotoxic metabolite, or metabolites, the identity of which remains unclear. alpha-Methyldopamine (alpha-MeDA) is a major metabolite of both MDA and MDMA. We have shown that intracerebroventricular (icv) injection of 2,5-bis(glutathion-S-yl)-alpha-methyldopamine [2, 5-bis(glutathion-S-yl)-alpha-MeDA] causes decreases in serotonin concentrations in the striatum, cortex, and hippocampus, and neurobehavioral effects similar to those seen following MDA and MDMA administration. In contrast, although 5-(glutathion-S-yl)-alpha-methyldopamine [5-(glutathion-S-yl)-alpha-MeDA] and 5-(N-acetylcystein-S-yl)-alpha-methyldopamine [5-(N-acetylcystein-S-yl)-alpha-MeDA] produce neurobehavioral changes similar to those seen with MDA and MDMA, and acute changes in brain 5-HT and dopamine concentrations, neither conjugate caused long-term decreases in 5-HT concentrations. We now report that direct intrastriatal or intracortical administration of 5-(glutathion-S-yl)-alpha-MeDA (4 x 200 or 4 x 400 nmol), 5-(N-acetylcystein-S-yl)-alpha-MeDA (4 x 7 or 4 x 20 nmol), and 2, 5-bis(glutathion-S-yl)-alpha-MeDA (4 x 150 or 4 x 300 nmol) causes significant decreases in striatal and cortical 5-HT concentrations (7 days following the last injection). Interestingly, intrastriatal injection of 5-(glutathion-S-yl)-alpha-MeDA or 2, 5-bis(glutathion-S-yl)-alpha-MeDA, but not 5-(N-acetylcystein-S-yl)-alpha-methyldopamine, also caused decreases in 5-HT concentrations in the ipsilateral cortex. The same pattern of changes was seen when the conjugates were injected into the cortex. The effects of the thioether conjugates of alpha-MeDA were confined to 5-HT nerve terminal fields, since no significant changes in monoamine neurotransmitter levels were detected in brain regions enriched with 5-HT cell bodies (midbrain/diencephalon/telencephalon and pons/medulla). In addition, the effects of the conjugates were selective with respect to the serotonergic system, as no significant changes were seen in dopamine or norepinephrine concentrations. The results indicate that thioether conjugates of alpha-MeDA are selective serotonergic neurotoxicants. Nonetheless, a role for these conjugates in the toxicity observed following systemic administration of MDA and MDMA remains to be demonstrated, and requires further experimentation.

The neurotoxic effects of methylenedioxymethamphetamine (MDMA) and its metabolites on rat brain spheroids in culture

Rat whole-brain spheroids were used to assess the intrinsic neurotoxicity of methylenedioxy-methamphetamine (MDMA, Ecstasy) and two of its metabolites, dihydroxymethamphetamine (DHMA) and 6-hydroxy-MDMA (6-OH MDMA). Exposure of brain spheroids to MDMA or the metabolite 6-OH MDMA (up to 500 micromol/L) for 5 days in culture did not alter intracellular levels of glutathione (GSH), glial fibrillary acidic protein (GFAP) or serotonin (5-HT). In contrast, exposure to the metabolite DHMA, which can deplete intracellular thiols, significantly increased GSH levels (up to 170% of control) following exposure to 50 and 100 micromol/L DHMA. There was also a significant reduction in the levels of glial fibrillary acidic protein (GFAP) and GSH by DHMA at the highest concentration tested (500 micromol/L) but there was no effect on 5HT. This may constitute a sublethal neurotoxic compensatory response to DHMA in an attempt to replenish depleted intraneural GSH levels following metabolite exposure. Rat whole-brain spheroids may thus be a useful in vitro model to delineate mechanisms and effects of this class of neurotoxin.

The acute effect in rats of 3,4-methylenedioxyethamphetamine (MDEA, "eve") on body temperature and long term degeneration of 5-HT neurones in brain: a comparison with MDMA ("ecstasy")

Administration of a single dose of the recreationally used drug 3,4-methylenedioxyethamphetamine (MDEA or "eve") to Dark Agouti rats resulted in an acute dose-dependent hyperthermic response. The peak effect and duration of hyperthermia of a dose of MDEA of 35 mg/kg intraperitoneally was similar to a dose of 3,4-methylenedioxymethamphetamine (MDMA or "ecstasy") of 15 mg/kg intraperitoneally. Seven days later this dose of MDMA produced a marked (approximately 50%) loss of 5-HT and its metabolite 5-HIAA in cortex, hippocampus and striatum and a similar loss of [3H]-paroxetine binding in cortex: these losses reflecting the MDMA-induced neurotoxic degeneration of 5-HT nerve endings. In contrast, administration of MDEA (15, 25 or 35 mg/kg), even at the highest dose, produced only a 20% loss in cortex and hippocampus and no decrease in striatum. The neurotoxic effect of MDEA was only weakly dose-dependent. Neither MDEA (35 mg/kg) nor MDMA (15 mg/kg) altered striatal dopamine content 7 days later. MDEA appeared to have about half the potency of MDMA in inducing acute hyperthermia and 25% of the potency in inducing degeneration of cerebral 5-HT neurones. However since higher doses of MDEA (compared to MDMA) are probably necessary to induce mood changing effects, these data do not support any contention that this compound is a "safer" recreational drug than MDMA in terms of either acute toxicity or long term neurodegeneration.

Amphetamines induce apoptosis and regulation of bcl-x splice variants in neocortical neurons

Amphetamineanalogs have emerged as popular recreational drugs of abuse. The number of reports of these substances producing severe acute toxicity and death is increasing. In 'Ecstasy' -associated deaths, focal necrosis in the liver and individual myocytic necrosis has been reported. Furthermore, serotonergic and dopaminergic neuronal cell damage has been observed in experimental amphetamine intoxication in laboratory animals. Here we demonstrate that subchronic exposure to D-amphetamine, methamphetamine, methylenedioxyamphetamine, and methylenedioxymethamphetamine ('Ecstasy') results in significant neurotoxicity in rat neocortical neurons in vitro. This neuronal cell death is accompanied by endonucleosomal DNA cleavage and differential expression of anti- and proapoptotic bcl-xL/S splice variants. In addition, we observed pronounced induction of cell stress-associated transcription factor c-jun and translation initiation inhibitor p97 after amphetamine treatment. These data support that the neurotoxic effects of different amphetamines are extended to rat neocortical neurons and that apoptotic pathways are involved in amphetamine-induced neurotoxicity.

3,4-Methylenedioxy analogues of amphetamine: defining the risks to humans

The 3,4-methylenedioxy analogues of amphetamine [MDMA ("Ecstasy", "Adam"), MDA ("Love") and MDE ("Eve")] are recreational drugs that produce feelings of euphoria and energy and a desire to socialize, which go far to explain their current popularity as "rave drugs". In addition to these positive effects, the drugs are relatively inexpensive to purchase and have the reputation of being safe compared to other recreational drugs. Yet there is mounting evidence that these drugs do not deserve this reputation of being safe. This review examines the relevant human and animal literature to delineate the possible risks MDMA, MDA and MDE engender with oral consumption in humans. Following a summary of the behavioral and cognitive effects of MDMA, MDA and MDE, risks will be discussed in terms of toxicity, psychopathology, neurotoxicity, abuse potential and the potential for drug-drug interactions associated with acute and chronic use.

2,5-Bis-(glutathion-S-yl)-alpha-methyldopamine, a putative metabolite of (+/-)-3,4-methylenedioxyamphetamine, decreases brain serotonin concentrations

3,4-(+/-)-Methylenedioxyamphetamine (MDA) and 3,4-(+/-)-methylenedioxymethamphetamine (MDMA) are serotonergic neurotoxicants. However, when injected directly into brain, MDA and MDMA are not neurotoxic, suggesting that systemic metabolism plays an important role in the development of neurotoxicity. The nature of the metabolite(s) responsible for MDA- and MDMA-mediated neurotoxicity is unclear. alpha-Methyldopamine is a major metabolite of MDA and is readily oxidized to the o-quinone, followed by conjugation with glutathione (GSH). Because the conjugation of quinones with GSH frequently results in preservation or enhancement of biological (re)activity, we have been investigating the role of quinone-thioethers in the acute and long-term neurochemical changes observed after administration of MDA. Although intracerebroventricular (i.c.v.) administration of 5-(glutathion-S-yl)-alpha-methyldopamine (4 x 720 nmol) and 5-(N-acetylcystein-S-yl)-alpha-methyldopamine (1 x 7 nmol) to Sprague-Dawley rats produced overt behavioral changes similar to those seen following administration of MDA (93 mumol/kg, s.c.) they did not produce long-term decreases in brain serotonin (5-hydroxytryptamine, 5-HT) concentrations. In contrast, 2,5-bis-(glutathion-S-yl)-alpha-methyldopamine (4 x 475 nmol) decreased 5-HT levels by 24%, 65% and 30% in the striatum, hippocampus and cortex, respectively, 7 days after injection. The relative sensitivity of the striatum, hippocampus and cortex to 2,5-bis-(glutathion-S-yl)-alpha-methyldopamine was the same as that observed for MDA; the absolute effects were greater with MDA. The effects of 2,5-bis-(glutathion-S-yl)-alpha-methyldopamine were also selective for serotonergic nerve terminal fields, in that 5-HT levels were unaffected in regions of the cell bodies. Because 2,5-bis-(glutathion-S-yl)-alpha-methyldopamine caused long-term depletion in 5-HT without adversely affecting the dopaminergic system, it also mimics the selectivity of MDA/MDMA. The data imply a possible role for quinone-thioethers in the neurobehavioral and neurotoxicological effects of MDA/MDMA.

Analysis of the enantiomers of 3,4-methylenedioxy-N-ethylamphetamine (MDE, "Eve") and its metabolite 3,4-methylenedioxyamphetamine (MDA) in rat brain

The methylenedioxy analogues of amphetamine are used recreationally despite concerns raised regarding potential neurotoxicity of the parent compounds and a number of metabolites. Much has been written regarding 3,4-methylenedioxymethamphetamine (MDMA; 3,4-methylenedioxy-N-ethylamphetamine (MDE; "Eve"), despite recent reports indicating the abuse of this drug and its potentially serious side effects. An assay procedure was developed for the simultaneous quantitation of both enantiomers of MDE and its metabolite MDA; the method involves derivatization with an optically pure reagent and analysis on a gas chromatograph equipped with a capillary column and a nitrogen-phosphorus detector. Brain levels of the enantiomers of MDE and MDA were examined in the rat at different time periods after acute i.p. injections of racemic MDE and the results were compared with levels of MDMA and MDA obtained after i.p. injection of MDMA in a previous study from our laboratories. The levels of the enantiomers of MDE and MDA achieved at 1, 4, and 8 hr were lower than in the case of MDMA. Stereoselective differences in brain levels of enantiomers of the parent drug and metabolite were much less marked with MDE than with MDMA, but where these small differences did exist in the case of MDE, the (R)-(-) vs (S)-(+) relationship was opposite to that reported for MDMA.

The hyperthermic and neurotoxic effects of 'Ecstasy' (MDMA) and 3,4 methylenedioxyamphetamine (MDA) in the Dark Agouti (DA) rat, a model of the CYP2D6 poor metabolizer phenotype

1. The effect of administration of 3,4-methylenedioxymethamphetamine (MDMA or 'Ecstasy') and its N-demethylated product, 3,4-methylenedioxyamphetamine (MDA) on both rectal temperature and long term neurotoxic loss of cerebral 5-hydroxytryptamine (5-HT) has been studied in male and female Dark Agouti (DA) rats. The female metabolizes debrisoquine more slowly than the male and its use has been suggested as a model of the human debrisoquine 4-hydroxylase poor metabolizer phenotype. 2. A novel h.p.l.c. method was developed and used to measure plasma MDMA and MDA concentrations in the DA rats. 3. The hyperthermic response following MDMA was enhanced in female rats. Plasma MDMA concentrations were also 57% higher than in males 45 min post-injection, while plasma concentrations of MDA were 48% lower. 4. Plasma concentrations of MDMA and MDA in male rats were unaffected by pretreatment with proadifen (15 mg kg-1) or quinidine (60 mg kg-1), but the hyperthermic response to MDMA (10 mg kg-1, i.p.) was enhanced by quinidine pretreatment. 5. The hyperthermic response following MDA was greater in male DA rats, despite plasma drug concentrations being 40% higher in females 60 min after injection. 6. Seven days after a single dose of MDMA (10 mg kg-1, i.p.) there was a substantial loss in the concentration of 5-HT and 5-hydroxyindoleacetic acid (5-HIA) in cortex and hippocampus. [3H]-paroxetine binding was also decreased by 27% in the cortex, indicating that the amine loss reflected a neurodegenerative change. MDMA (5 mg kg-1, i.p.) was without effect on brain 5-HT content. content.7. A single dose of MDA (5 mg kg-1, i.p.) produced a major (approximately 40%) loss of 5-HT content of cortex and hippocampus 7 days later. The loss was similar in males and females.8 These data demonstrate that female DA rats are more susceptible to the acute hyperthermic effects ofMDMA, probably because of impaired N-demethylation and indicate that in human subjects acuteMDMA-induced toxicity may be exacerbated in poor metabolizer phenotypes. Low debrisoquine hydroxylase activity did not appear to impair the formation of a MDMA or MDA neurotoxic metabolite. Both severe acute hyperthermia and delayed neurotoxicity occurred following plasma levels of MDMA comparable to those reported in persons misusing the drug.

Behavioral and developmental effects of two 3,4-methylenedioxymethamphetamine (MDMA) derivatives

The effects of 3,4-methylenedioxymethamphetamine (MDMA or 'ecstacy') and two structurally related compounds, N-methyl-1-(3,4-methylenedioxyphenyl)-1-ethanamine (MDM1EA) and N-methyl-1-(3,4-methylenedioxyphenyl)-3-butanamine (HMDMA) were examined in two preparations: (i) a drug discrimination procedure in MDMA-trained rats and (ii) the chicken embryo, for determination of the direct effects of these compounds on the developing organism. The highest doses of MDM1EA and HMDMA partially substituted for MDMA, whereas higher (30-60 mg/kg) doses of HMDMA evoked clonic seizures in a separate group of rats. In chicken embryos MDMA had no effect on body, brain or liver weight, while the highest dose of MDM1EA decreased body weight and the 2 lowest doses of HMDMA increased body weight. All doses of HMDMA decreased liver weight (expressed as % body weight) when compared with contemporaneous water-treated controls. Taken together, the results of these experiments suggest that structurally related compounds share some stimulus properties with MDMA and may therefore share abuse liability. Furthermore, both MDMA-related compounds produced adverse effects on the developing organism, whereas MDMA did not.

Methylenedioxyamphetamine: a selective effect on cortical content and turnover of 5-HT

This study examined the effects of the hallucinogen, MDA, on brain content of monoamines and their metabolites in the rabbit. A single 1.8 mg/kg dose of MDA produced 30 to 64% increases in the 5-HT content of frontal cortex from 30 to 120 min after injection and a decrease in 5-HT turnover from 30 min to 8 h, but had no effect in hippocampus, caudate nucleus, or hypothalamus. A single 3.6 mg/kg dose of MDA also reduced the turnover of 5-HT in frontal cortex, but this was accompanied by a decrease in 5-HIAA with no increase in 5-HT. The 1.8 and 3.6 mg/kg doses of MDA had no significant or consistent effects on the contents of DA, DOPAC, HVA, and NE in any brain area examined. Chronic administration of MDA (3.6 mg/kg/day for 4 days) failed to produce any evidence of a neurotoxic action on 5-HT neurons. Higher doses could not be employed because the LD50 of MDA was approximately 5 mg/kg. This study has demonstrated that behaviorally effective and nonneurotoxic doses of MDA produce increases in the content and decreases in turnover of 5-HT in frontal cortex that resemble those of other hallucinogens such as LSD and DOM.

CuZn-superoxide dismutase (CuZnSOD) transgenic mice show resistance to the lethal effects of methylenedioxyamphetamine (MDA) and of methylenedioxymethamphetamine (MDMA)

We have used female and male transgenic (Tg) mice that carry the complete sequence of the human copper-zinc (CuZn) superoxide dismutase (SOD) gene in order to assess the lethal effects of methylenedioxyamphetamine (MDA) and methylenedioxymethamphetamine (MDMA). In contrast to non-Tg mice, both heterozygous and homozygous SOD-Tg mice showed resistance to the lethal effects of both drugs. Females of both SOD-Tg and non-Tg strains were somewhat more resistant to the effects of these drugs in comparison to males. In general, homozygous animals show greater resistance to the effects of the two drugs. These results suggest that the acute lethal effects of amphetamine-substituted analogs might involve the intracellular overproduction of the superoxide radicals secondary to hypoxic injury. The gender differences suggest that there might be hormonal-free radical scavenger interactions that offer better protection to female mice. This might be related both to the lifespan of and to the lower prevalence of Parkinson's disease in women. Future studies will need to address these issues further.

Modeling for risk assessment of neurotoxic effects

The regulation of noncancer toxicants, including neurotoxicants, has usually been based upon a reference dose (allowable daily intake). A reference dose is obtained by dividing a no-observed-effect level by uncertainty (safety) factors to account for intraspecies and interspecies sensitivities to a chemical. It is assumed that the risk at the reference dose is negligible, but no attempt generally is made to estimate the risk at the reference dose. A procedure is outlined that provides estimates of risk as a function of dose. The first step is to establish a mathematical relationship between a biological effect and the dose of a chemical. Knowledge of biological mechanisms and/or pharmacokinetics can assist in the choice of plausible mathematical models. The mathematical model provides estimates of average responses as a function of dose. Secondly, estimates of risk require selection of a distribution of individual responses about the average response given by the mathematical model. In the case of a normal or lognormal distribution, only an estimate of the standard deviation is needed. The third step is to define an adverse level for a response so that the probability (risk) of exceeding that level can be estimated as a function of dose. Because a firm response level often cannot be established at which adverse biological effects occur, it may be necessary to at least establish an abnormal response level that only a small proportion of individuals would exceed in an unexposed group. That is, if a normal range of responses can be established, then the probability (risk) of abnormal responses can be estimated.(ABSTRACT TRUNCATED AT 250 WORDS)

3,4-Methylenedioxymethamphetamine (MDMA, "Ecstasy"): pharmacology and toxicology in animals and humans

(+/-)3,4-Methylenedioxymethamphetamine (MDMA, "Ecstasy"), a ring-substituted amphetamine derivative first synthesized in 1914, has emerged as a popular recreational drug of abuse over the last decade. Pharmacological studies indicate that MDMA produces a mixture of central stimulant and psychedelic effects, many of which appear to be mediated by brain monoamines, particularly serotonin and dopamine. In addition to its pharmacologic actions, MDMA has been found to possess toxic activity toward brain serotonin neurones. Serotonergic neurotoxicity after MDMA has been demonstrated in a variety of experimental animals (including non-human primates). In monkeys, the neurotoxic dose of MDMA closely approaches that used by humans. While the possibility that MDMA is also neurotoxic in humans is under investigation, other adverse effects of MDMA in humans have been documented, including various systemic complications and a number of untoward neuropsychiatric sequelae. Notably, many of the adverse neuropsychiatric consequences noted after MDMA involve behavioral domains putatively influenced by brain serotonin (e.g., mood, cognition and anxiety). Given the restricted status of MDMA use, retrospective clinical observations from suspecting clinicians will probably continue to be a primary source of information regarding MDMA's effects in humans. As such, this article is intended to familiarize the reader with the behavioral pharmacology and toxicology of MDMA, with the hope that improved recognition of MDMA-related syndromes will provide insight into the function of serotonin in the human brain, in health as well as disease.

Serotonin neurotoxicity after (+/-)3,4-methylenedioxymethamphetamine (MDMA; "Ecstasy"): a controlled study in humans

(+/-)3,4-Methylenedioxymethamphetamine (MDMA; "Ecstasy"), an increasingly popular recreational drug, is known to damage brain serotonin 5-hydroxytryptamine (5-HT) neurons in experimental animals. Whether MDMA is neurotoxic in humans has not been established. Thirty MDMA users and 28 controls were admitted to a controlled inpatient setting for measurement of biologic and behavioral indexes of central 5-HT function. Outcome measures obtained after at least 2 weeks of drug abstinence included concentrations of monoamine metabolites in cerebrospinal fluid (CSF), prolactin responses to L-tryptophan, nociceptive responses to ischemic pain, and personality characteristics in which 5-HT has been implicated (i.e., impulsivity and aggression). Subjects with a history of MDMA exposure had lower levels of CSF 5-hydroxyindoleacetic acid (the major metabolite of 5-HT) than controls (p = .001). Although they resembled controls in their prolactin response to L-tryptophan and their response to ischemic pain, MDMA users had lower scores on personality measures of impulsivity (p = .004) and indirect hostility (p = .009). The CSF findings suggest that 5-HT neurotoxicity may be a potential complication of MDMA use. Further, differences in personality support the view that 5-HT systems are involved in modulating impulsive and aggressive personality traits. Additional studies of MDMA-exposed individuals are needed to confirm and extend the present findings. Such studies could help elucidate the role of 5-HT in normal brain function as well as in neuropsychiatric disease states.

A study of the mechanism of MDMA ('ecstasy')-induced neurotoxicity of 5-HT neurones using chlormethiazole, dizocilpine and other protective compounds

1. An investigation has been made in rats into the neurotoxic effect of the relatively selective 5-hydroxytryptamine (5-HT) neurotoxin, 3,4-methylenedioxymethamphetamine (MDMA or 'Ecstasy') using chlormethiazole and dizocilpine, both known neuroprotective compounds and also gamma-butyrolactone, ondansetron and pentobarbitone. 2. Administration of MDMA (20 mg kg-1, i.p.) resulted in a 50% loss of cortical and hippocampal 5-HT and 5-hydroxyindole acetic acid (5-HIAA) 4 days later. This reflects the long term neurotoxic loss of 5-HT that occurs. Injection of gamma-butyrolactone (GBL; 400 mg kg-1, i.p.) 5 min before and 55 min after the MDMA provided substantial protection. Pentobarbitone (25 mg kg-1, i.p.) using the same dose regime was also protective, but ondansetron (0.5 mg kg-1 or 0.1 mg kg-1, i.p.) was without effect. 3. MDMA (20 mg kg-1) had no significant effect on striatal dopamine concentration 4 days later but did produce a small decrease in 3,4-dihydroxyphenylacetic acid (DOPAC) content. There were few significant changes in rats given MDMA plus GBL, ondansetron or pentobarbitone. 4. A single injection of MDMA (20 mg kg-1, i.p.) resulted in a greater than 80% depletion of 5-HT in hippocampus and cortex 4 h later, reflecting the initial rapid release that had occurred. None of the neuroprotective compounds (chlormethiazole, 50 mg kg-1; dizocilpine, 1 mg kg-1; GBL, 400 mg kg-1; pentobarbitone, 25 mg kg-1) given 5 min before and 55 min after the MDMA injection, altered the degree of 5-HT loss. 5. Acute MDMA injection increased striatal dopamine content (28%) and decreased the DOPAC content. In general, administration of the drugs under investigation did not significantly alter these MDMA-induced changes. Both chlormethiazole and GBL produced a greater increase in dopamine than MDMA alone, but this was apparently an additive effect to the action of either drug alone. 6. The 5-HT loss 4 h following administration of the neurotoxin p-chloroamphetamine (2.5 mg kg-1,i.p.) was not affected by chlormethiazole or dizocilpine. p-Chloroamphetamine did not appear to alter striatal dopamine metabolism.7. None of the protective drugs inhibited the initial 5-HT loss following MDMA, rendering unlikely any proposal that they are protective because they inhibit 5-HT release and the subsequent formation ofa toxic indole derivative. All the protective compounds (unlike ondansetron) probably inhibit dopamine release in the striatum. Since the neurotoxic action of some substituted amphetamines is dependent on the integrity of nigro-striatal neurones, this fact may go some way to explain the protective action of this diverse group of compounds.

Persistent effects of (+/- )3,4-methylenedioxymethamphetamine (MDMA, "ecstasy") on human sleep

(+/- )3,4-methylenedioxymethamphetamine (MDMA) is a recreational drug of abuse which damages serotonin neurons in animals. It is not known whether MDMA is also neurotoxic in humans, and if so, whether there are functional consequences. Given the putative role of serotonin in sleep, it was hypothesized that one manifestation of serotonin neurotoxicity in humans might be disturbances of sleep. To determine whether MDMA use has effects on sleep, all-night polysomnograms of 23 MDMA users were compared to those of 22 age- and sex-matched controls. On average, MDMA users had 19 minutes less total sleep and 23.2 minutes less non-REM (NREM) sleep than controls. These statistically significant differences in NREM sleep were due primarily to an average of 37 minutes less stage 2 sleep, with no significant differences noted in stages 1, 3 or 4. Although it is not known whether the alterations in sleep observed in MDMA users are due to serotonin neurotoxicity, the present findings suggest that MDMA use can lead to persistent changes in CNS structures involved in human sleep generation.

Methylenedioxyamphetamine: neurotoxic effects on serotonergic projections to brainstem nuclei in the rat

This study employed immunocytochemistry to visualize the neurotoxic effects of methylenedioxyamphetamine hydrochloride (MDA) on serotonergic projections to brainstem structures. Separate groups of animals were injected twice a day, for 4 consecutive days, with: saline; MDA (40 mg/kg/day); or fluoxetine hydrochloride (10 mg/kg) prior to each injection of MDA. In agreement with previous reports, MDA produced a pronounced loss of 5-HT immunoreactivity in the forebrain, most notably in neocortex and hippocampus. However, our results revealed that MDA also produced a loss of 5-HT fibers in brainstem that was as severe as that seen in any region of forebrain. Regions most severely affected included: superior colliculus; superior olivary complex; trigeminal sensory complex and vestibular nuclei. The brains of animals treated with MDA demonstrated a relative absence of fine 5-HT axon terminals within these forebrain and brainstem regions, while thicker axonal elements were still present. The neurotoxic effects of MDA on serotonergic projections to forebrain and brainstem were completely blocked by the prior administration of the 5-HT reuptake inhibitor, fluoxetine. It was suggested that the denervation of the superior colliculus, superior olive and vestibular nuclei could alter visually guided eye movements and the vestibulo-ocular reflex while the loss of serotonergic inputs to the trigeminal sensory complex might be expected to alter tactual reflexes.

Caveats regarding the use of the laboratory rat as a model for acute toxicological studies: modulation of the toxic response via physiological and behavioral mechanisms

The rodent, specifically the laboratory rat, is the primary experimental animal used in toxicology testing. Despite its popularity, recent studies from our laboratory and others raise a number of questions concerning the rat's appropriateness as an animal model for toxicological studies. While there may be additional areas in which the rat and other small rodents fail to adequately mimic the human response to xenobiotic agents, this article will focus on the area of temperature regulation. Thus, this article will review the thermoregulatory response of the laboratory rat following acute exposure to toxic agents and examine the impact of this response on the extrapolation of toxicological data from experimental animals to humans. In general, the rat responds to acute intoxication by lowering its core temperature via both physiological and behavioral mechanisms, thereby attenuating the induced toxicity. Similar responses have not been reported in humans.

Effect of acute monoamine depletion on 3,4-methylenedioxymethamphetamine-induced neurotoxicity

The effect of acute, reversible depletion of either serotonin [5-hydroxytryptamine (5-HT)] or dopamine (DA) on the long-term (7-day) decrease of brain 5-HT content produced after 3,4-methylenedioxymethamphetamine (MDMA) administration was investigated. The tyrosine hydroxylase inhibitor alpha-methyl-p-tyrosine (alpha-MPT) significantly attenuated the acute increase in DA efflux produced by MDMA in the striatum as measured by in vivo microdialysis. Treatment with alpha-MPT had no effect on MDMA-induced 5-HT release. alpha-MPT treatment blocked the long-term (7-day) depletion of striatal 5-HT content after MDMA administration. The tryptophan hydroxylase inhibitor p-chlorophenylalanine (PCPA) completely blocked the acute increase in the extracellular concentration of 5-HT produced by MDMA. Although PCPA significantly attenuated the increase in DA efflux produced by MDMA, the effect was small in magnitude. More importantly, treatment with PCPA had no effect on MDMA-induced decrease of 5-HT uptake sites in the frontal cortex. These data are suggestive that acute depletion of DA but not 5-HT protects against the long-term neurotoxic effects of MDMA on 5-HT axon terminals. In addition, these data are supportive of the hypothesis that DA plays a major role in the neurotoxic effects of MDMA.

Reinforcing subjective effects of (+/-) 3,4-methylenedioxymethamphetamine ("ecstasy") may be separable from its neurotoxic actions: clinical evidence

(+/-)3,4-Methylenedioxymethamphetamine (MDMA), a synthetic amphetamine derivative used recreationally by humans, damages brain serotonin neurons in experimental animals. In preclinical studies, serotonin reuptake inhibitors block MDMA-induced serotonin release; they also block MDMA neurotoxicity. Whether serotonin reuptake inhibitors also block MDMA's psychoactive effects in humans has not been established. Reported herein are four individuals who describe their experiences after ingesting fluoxetine, a potent and selective serotonin reuptake inhibitor, before MDMA ingestion. Their reports indicate that fluoxetine does not block MDMA's reinforcing subjective effects and raise the possibility that MDMA's psychoactive effects may be separable from its neurotoxic actions.

Serotonergic recovery after (+/-)3,4-(methylenedioxy) methamphetamine injury: observations in rats

(+/-)-3,4-Methylenedioxymethamphetamine (MDMA) is a recreational drug of abuse which damages serotonin (5-HT) neurons in animals. In monkeys, the damage appears to be permanent. By contrast, in rats there is indication that neuronal recovery takes place, although there is question as to whether the recovery is sustained. The purpose of the present study was to examine the fate of 5-HT neurons in MDMA-treated rats, and to compare findings in the rat with those in the monkey. Rats were treated with MDMA (10 mg/kg i.p.) every 2 hr for a total dose of 40 mg/kg. Two, 8, 16, 32 and 52 weeks later, groups (n = 8) of MDMA-treated rats, along with age-matched controls (n = 8), were analyzed for regional brain 5-HT, 5-hydroxyindoleacetic acid and [3H]paroxetine-labeled 5-HT uptake sites. Two weeks after MDMA, 5-HT neuronal markers were reduced markedly. Reductions ranged from 42 to 82% depending on brain region. By 16 weeks, there was evidence of recovery in some brain regions (e.g., hypothalamus and striatum) and by 32 weeks, recovery was nearly complete in most brain regions examined. One year after MDMA, recovery was still evidence in all brain regions evaluated, although closer inspection of the group data revealed that whereas most MDMA-treated rats recovered, some did not. These few animals had severe and enduring serotonergic deficits in multiple brain regions. Morphologic immunocytochemical studies yielded results which corroborated the neurochemical findings.(ABSTRACT TRUNCATED AT 250 WORDS)

5-HT loss in rat brain following 3,4-methylenedioxymethamphetamine (MDMA), p-chloroamphetamine and fenfluramine administration and effects of chlormethiazole and dizocilpine

1. The present study has investigated whether the neurotoxic effects of the relatively selective 5-hydroxytryptamine (5-HT) neurotoxins, 3,4-methylenedioxymethamphetamine (MDMA or 'Ecstasy'), p-chloroamphetamine (PCA) and fenfluramine on hippocampal and cortical 5-HT terminals in rat brain could be prevented by administration of either chlormethiazole or dizocilpine. 2. Administration of MDMA (20 mg kg-1, i.p.) resulted in an approximate 30% loss of cortical and hippocampal 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) content 4 days later. Injection of chlormethiazole (50 mg kg-1) 5 min before and 55 min after the MDMA provided complete protection in both regions, while dizocilpine (1 mg kg-1, i.p.) protected only the hippocampus. 3. Administration of a single dose of chlormethiazole (100 mg kg-1) 20 min after the MDMA also provided complete protection to the hippocampus but not the cortex. This regime also attenuated the sustained hyperthermia (approx +2.5 degrees C) induced by the MDMA injection. 4. Injection of PCA (5 mg kg-1, i.p.) resulted in a 70% loss of 5-HT and 5-HIAA content in hippocampus and cortex 4 days later. Injection of chlormethiazole (100 mg kg-1, i.p.) or dizocilpine (1 mg kg-1, i.p.) 5 min before and 55 min after the PCA failed to protect against the neurotoxicity, nor was protection afforded by chlormethiazole when a lower dose of PCA (2.5 mg kg-1, i.p.) was given which produced only a 30% loss of 5-HT content. Chlormethiazole did prevent the hyperthermia induced by PCA (5 mg kg-1), while the lower dose of PCA (2.5 mg kg-1) did not produce a change in body temperature.5. Neither chlormethiazole nor dizocilpine prevented the neurotoxic loss of hippocampal or cortical 5-HT neurones measured 4 days following administration of fenfluramine (25 mg kg-1, i.p.).6. In general, chlormethiazole and dizocilpine were effective antagonists of the 5-HT-mediated behaviours of head weaving and forepaw treading which appeared following injection of all three neurotoxins.7. Both chlormethiazole and dizocilpine have previously been shown to prevent the neurotoxic effects ofa high dose of methamphetamine on cerebral 5-HT and dopamine pathways. These drugs also prevent MDMA-induced neurotoxicity of 5-HT pathways, but not that induced by injection of PCA or fenfluramine. This suggests that the mechanisms of neurotoxic damage to 5-HT pathways produced by substituted amphetamines cannot be identical. The monoamine loss does not appear to result from the hyperthermia produced by the neurotoxic compounds.

Methamphetamine neurotoxicity and striatal glutamate release: comparison to 3,4-methylenedioxymethamphetamine

The effect of repeated administration of either methamphetamine (MA), 3,4-methylenedioxymethamphetamine (MDMA) or vehicle on the extracellular concentrations of glutamate (GLU), aspartate, taurine, dopamine (DA) and its metabolite, 3,4-dihydroxyphenylacetic acid (DOPAC), was studied in awake, freely moving rats using in vivo microdialysis. MA (7.5 mg/kg, i.p.) administered every 2 h for a total of 3 injections, increased the extracellular concentration of GLU in the anteromedial striatum. By contrast, neither vehicle nor MDMA (9.2 and 13.8 mg/kg) increased GLU efflux following repeated administration. Both MA and MDMA increased the extracellular concentration of DA in the striatum. However, the cumulative increase in DA was significantly greater in the MDMA treated animals as compared to the MA group. The concentrations of DA, serotonin (5-HT) and their metabolites were determined in the striatum 7 days following the repeated administration of MA, MDMA and vehicle. MA, but not MDMA or vehicle, decreased the concentration of DA in the striatum. Conversely, MDMA (13.8 mg/kg) decreased the concentration of 5-HT, whereas MA, MDMA (9.2 mg/kg) and vehicle had no effect on striatal 5-HT content. These data are suggestive that the long-term (7 day) DA neurotoxicity produced by the repeated administration of MA is mediated, in part, by a delayed increase in extracellular concentrations of GLU. In contrast, repeated administration of MDMA, at a dose which produced a long-term (7 day) depletion of striatal 5-HT content, had no effect on GLU efflux in the striatum.

Long-term alteration in the central monoaminergic systems of the rat by 2,4,5-trihydroxyamphetamine but not by 2-hydroxy-4,5-methylenedioxymethamphetamine or2-hydroxy-4,5-methylenedioxyamphetamine

The long-term effects of three metabolites of 3,4-methylenedioxymethamphetamine (MDMA) on the central monoaminergic systems of the rat were examined. Seven days after the intracerebroventricular administration of 0.25 and 0.5 mumol 2,4,5-trihydroxyamphetamine, hippocampal tryptophan hydroxylase (TPH) activity was reduced to 5 and 1% of control, respectively, while norepinephrine (NE) concentration was depressed to 10 and 18% of control. These two respective dosages also decreased striatal tyrosine hydroxylase (TH) activity to 67 and 10% of control, respectively, while nigral TH activity was reduced to 59 and 20% of control. Striatal TPH activity was reduced to 74 and 81% of control, respectively, while the activity in the dorsal and median raphe remained unaltered. The intracerebroventricular administration of 1 mumol 2-hydroxy-4,5-methylenedioxymethamphetamine (6-OH-MDMA) failed to alter TPH activity, TH activity or NE concentration after 14 days. In contrast, 1 mumol of 2-hydroxy-4,5-methylenedioxyamphetamine (6-OH-MDA) induced a 30% increase in striatal TPH activity and a 50% increase in nigral TH activity. The study of the formation of 2,4,5-trihydroxyamphetamine after MDMA treatment may provide insight as to how MDMA destroys serotonergic nerve terminals.

Effects of benzylpiperazine derivatives on the neurotoxicity of 3,4-methylenedioxymethamphetamine in rat brain

The neurotoxicity of 3,4-methylenedioxymethamphetamine (MDMA) in rat brain was attenuated significantly by coadministration of several benzylpiperazines (p-nitrobenzylpiperazine, p-chlorobenzylpiperazine and 1-piperonylpiperazine), which were weak inhibitors for [3H]6-nitroquipazine binding to the 5-hydroxytryptamine (5-HT) transporter in rat brain. These results suggest that these benzylpiperazines may inhibit the MDMA-induced neurotoxicity by a novel neuropharmacological effect other than 5-HT uptake inhibition.

Evaluation of the neurotoxicity of N-methyl-1-(4-methoxyphenyl)-2-aminopropane (para-methoxymethamphetamine, PMMA)

These studies assessed the neurotoxic potential of N-methyl-1-(4-methoxyphenyl)-2-aminopropane (para-methoxymethamphetamine; PMMA), an amphetamine analog that has surfaced in the illicit drug market. Repeated subcutaneous injections of PMMA caused lasting, dose-related reductions in regional brain concentrations of serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA), and in the density of [3H]paroxetine-labelled 5-HT uptake sites. Comparison of the neurotoxic potential of PMMA to that of para-methoxyamphetamine (PMA) and 3,4-methyl-enedioxymethamphetamine (MDMA) showed that equivalent doses of PMMA and PMA (80 mg/kg) produced comparable depletions of 5-HT, but that these depletions were not as pronounced as those induced by a lower dose of MDMA (20 mg/kg). Striatal DA was not affected on a long-term basis by any of the ring-substituted amphetamines evaluated in this study. These data suggest that PMMA, like PMA and MDMA, produces long-term (possibly neurotoxic) effects on brain serotonin neurons, but that PMMA is less potent than MDMA as a 5-HT neurotoxin. Further, they raise concern over the illicit use of PMMA since humans could be more sensitive than rodents to the 5-HT neurotoxic effects of PMMA and related drugs.

Antagonism of 3,4-methylenedioxymethamphetamine-induced neurotoxicity in rat brain by 1-piperonylpiperazine

The effects of 1-piperonylpiperazine and N,alpha-dimethylpiperonylamine, which are weak inhibitors for [3H]5-hydroxytryptamine (5-HT) uptake, on 3,4-methylenedioxymethamphetamine (MDMA)-induced neurotoxicity were examined. The reductions of serotonergic parameters in the rat cerebral cortex produced by multiple administration of MDMA (10 mg/kg) were attenuated significantly by coadministration of 6-nitroquipazine (10 mg/kg), paroxetine (10 mg/kg) or 1-piperonylpiperazine (20 mg/kg), but not by N,alpha-dimethylpiperonylamine (20 mg/kg). The present data suggest that 1-piperonylpiperazine might inhibit the MDMA-induced neurotoxicity by effect(s) other than 5-HT uptake inhibition.