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

The Effects of 3,4-methylenedioxymethamphetamine on Neurogenesis in the Hippocampus of Male Rats

Introduction:

The administration of 3,4-methylenedioxymethamphetamine (MDMA) or ecstasy causes memory impairment, whereas neurogenesis improves memory and learning. Hence, this study evaluated the effects of MDMA on neurogenesis in the hippocampus of male rats.

Methods:

Adult male Wistar rats received Intraperitoneal (IP) injections of MDMA (10 mg/ kg). We assessed nestin, sex-determining region Y-box 2 (Sox2), and NeuroD expressions according to the immunohistochemistry analyses.

Results:

MDMA reduced the expressions of nestin, Sox2, and NeuroD compared with the control groups. The reduction in NeuroD expression was age-related.

Conclusion:

MDMA possibly has negative effects on neurogenesis, which specifically results from impaired survival of newborn cells.

Increased iNOS and Nitrosative Stress in Dopaminergic Neurons of MDMA-Exposed Rats

Several mechanisms underlying 3,4-Methylenedioxy-N-methylamphetamine (MDMA) neurotoxicity have been proposed, including neurochemical alterations and excitotoxicity mediated by reactive oxygen species (ROS), nitric oxide (NO), and reactive nitrogen species (RNS). However, ROS, NO, and RNS sources in the brain are not fully known. We aimed to investigate possible alterations in the expression of the ROS producer NOX enzymes (NOX2, NOX1, and NOX4), NO generators (iNOS, eNOS, and nNOS), markers of oxidative (8-hydroxy-2'-deoxyguanosine, 8OHdG), and nitrosative (3-nitrotyrosine, NT) stress, as well as the colocalization between cells positive for the dopamine transporter (DT1) and cells expressing the neuronal nuclei (NeuN) marker, in the frontal cortex of rats receiving saline or MDMA, sacrificed 6 h, 16 h, or 24 h after its administration. MDMA did not affect NOX2, NOX1, and NOX4 immunoreactivity, whereas iNOS expression was enhanced. The number of NT-positive cells was increased in MDMA-exposed animals, whereas no differences were detected in 8OHdG expression among experimental groups. MDMA and NT markers colocalized with DT1 positive cells. DT1 immunostaining was found in NeuN-positive stained cells. Virtually no colocalization was observed with microglia and astrocytes. Moreover, MDMA immunostaining was not found in NOX2-positive cells. Our results suggest that iNOS-derived nitrosative stress, but not NOX enzymes, may have a crucial role in the pathogenesis of MDMA-induced neurotoxicity, highlighting the specificity of different enzymatic systems in the development of neuropathological alterations induced by the abuse of this psychoactive compound.

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

RATIONALE

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

The preclinical pharmacology of mephedrone; not just MDMA by another name

The substituted β-keto amphetamine mephedrone (4-methylmethcathinone) was banned in the UK in April 2010 but continues to be used recreationally in the UK and elsewhere. Users have compared its psychoactive effects to those of 3,4-methylenedioxymethamphetamine (MDMA, 'ecstasy'). This review critically examines the preclinical data on mephedrone that have appeared over the last 2-3 years and, where relevant, compares the pharmacological effects of mephedrone in experimental animals with those obtained following MDMA administration. Both mephedrone and MDMA enhance locomotor activity and change rectal temperature in rodents. However, both of these responses are of short duration following mephedrone compared with MDMA probably because mephedrone has a short plasma half-life and rapid metabolism. Mephedrone appears to have no pharmacologically active metabolites, unlike MDMA. There is also little evidence that mephedrone induces a neurotoxic decrease in monoamine concentration in rat or mouse brain, again in contrast to MDMA. Mephedrone and MDMA both induce release of dopamine and 5-HT in the brain as shown by in vivo and in vitro studies. The effect on 5-HT release in vivo is more marked with mephedrone even though both drugs have similar affinity for the dopamine and 5-HT transporters in vitro. The profile of action of mephedrone on monoamine receptors and transporters suggests it could have a high abuse liability and several studies have found that mephedrone supports self-administration at a higher rate than MDMA. Overall, current data suggest that mephedrone not only differs from MDMA in its pharmacological profile, behavioural and neurotoxic effects, but also differs from other cathinones.

Current preclinical studies on neuroinflammation and changes in blood-brain barrier integrity by MDMA and methamphetamine

The blood-brain barrier (BBB) is essential in the maintenance of brain homeostasis both by preserving normal brain functioning and also by protecting the brain from exposure to a range of potentially harmful substances. This review presents some of the evidence of BBB disruption following exposure to the substituted amphetamines 3,4-methylenedioxymethamphetamine (MDMA, 'ecstasy') and methamphetamine (METH), two drugs of abuse which are widely consumed recreationally by younger sectors of the population. Both MDMA and METH have been shown to produce disruption of the BBB as reflected by IgG extravasation and Evans Blue leakage. In particular, METH decreases the expression of basal lamina proteins associated with an increase in matrix metalloproteinase activity. These changes in BBB integrity appear to be related to MDMA-induced activation of the mitogen-activated protein kinase (MAPK) JNK1/2. The consequences of the disruption in the BBB by these two drugs remain to be established, but there is evidence in the literature that, at least in the case of METH, increased matrix metalloproteinase (MMP) activity may be related to increased behavioural sensitization and reward perhaps because of the modification of the passage of the drug into the CNS. In addition, the high incidence of AIDS-related neurologic disease in METH users may also be related to increased entry into the brain of virally derived neurotoxic products. This article is part of the Special Issue entitled 'CNS Stimulants'.

Effect of acute brain tyrosine depletion on MDMA-induced changes in brain 5-HT

The mechanism by which 3,4-methylenedioxymethamphetamine (MDMA) produces 5-hydroxytryptamine (5-HT, serotonin) neurotoxicity has been suggested to involve an acute release of tyrosine and its non-enzymatic conversion to dopamine. To determine whether brain tyrosine availability is important in MDMA-induced neurotoxicity, brain tyrosine was acutely depleted with a tyrosine-free amino acid mixture (1 g/kg intraperitoneal; twice 1 h apart) which was administered prior to an injection of MDMA (12.5 mg/kg intraperitoneal). A small increase in both the hippocampal and striatal tyrosine concentration occurred in control rats treated with MDMA. The tyrosine-free amino acid mixture significantly decreased tyrosine levels by more than 50% in both brain regions 2 h after injection of either MDMA or saline. MDMA significantly reduced brain 5-HT content 2 h later, but this was of a similar magnitude in control and tyrosine-depleted groups. The long-term neurotoxic 5-HT loss in the hippocampus induced two weeks after MDMA administration was unaltered by the tyrosine-free amino acid mixture. Striatal dopamine content was unaffected by acute MDMA in all groups, while the tyrosine-free amino acid mixture given with MDMA significantly decreased striatal dopamine content 2 weeks later. The tyrosine-free amino acid mixture given alone had no affect on rectal body temperature but attenuated the duration of MDMA-induced hyperthermia. The results confirmed the ability of systemic MDMA to acutely increase brain tyrosine content, but also indicated that a marked acute reduction of brain tyrosine does not directly affect either immediate 5-HT release (as measured by tissue depletion) or long-term hippocampal serotonergic neurotoxicity produced by MDMA.

Neurotoxicity of substituted amphetamines: Molecular and cellular mechanisms

The amphetamines, including amphetamine (AMPH), methamphetamine (METH) and 3,4-methylenedioxymethamphetamine (MDMA), are among abused drugs in the US and throughout the world. Their abuse is associated with severe neurologic and psychiatric adverse events including the development of psychotic states. These neuropsychiatric complications might, in part, be related to drug-induced neurotoxic effects, which include damage to dopaminergic and serotonergic terminals, neuronal apoptosis, as well as activated astroglial and microglial cells in the brain. The purpose of the present review is to summarize the toxic effects of AMPH, METH and MDMA. The paper also presents some of the factors that are thought to underlie this toxicity. These include oxidative stress, hyperthermia, excitotoxicity and various apoptotic pathways. Better understanding of the cellular and molecular mechanisms involved in their toxicity should help to generate modern therapeutic approaches to prevent or attenuate the long-term consequences of amphetamine use disorders in humans.

The effect of psychostimulants on [3H]dopamine uptake and release in rat brain synaptic vesicles

Amphetamine and its derivatives are psychostimulants active at the plasma membrane monoamine transporters. In the present study we assessed the interaction of parachloroamphetamine, D-amphetamine, fenfluramine and methylendioxymethamphetamine with brain vesicular monoamine transporter using purified rat striatal synaptic vesicles. All four psychostimulants inhibited vesicular [(3)H]dopamine uptake in a competitive and dose-dependent manner and had no effect on [(3)H]dihydrotetrabenazine binding. At higher concentrations the drugs enhanced [(3)H]dopamine vesicular efflux. Parachloroamphetamine was the most potent agent while methylendioxymethamphetamine was the weakest one. The vesicular activities may be relevant to their neurotoxicity.

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.

MDMA (Ecstasy) controls in concert a group of genes involved in GABA neurotransmission

In several countries, 3,4-methylenedioxymethamphetamine (MDMA) is currently the most abundant psychoactive recreational drug. MDMA induces numerous neuropsychiatric behaviors, serotonergic neuron degeneration, programmed death of cultured cells, hyperthermia and occasional fatality. Using gene expression analysis in MDMA-treated mice, we identified changes in gamma-amino butyric acid (GABA) transporters and synaptotagmins I and IV. Additional experiments showed decreases in mRNAs encoding septin and dystrophin. Although belonging to different gene families, it is striking that these four protein groups are implicated in neurotransmission of GABA, a major inhibitory neurotransmitter involved in thermoregulation. MDMA may control these genes in a combined fashion, assigning GABA a pivotal role in MDMA activities.

Multiple molecular and neuropharmacological effects of MDMA (Ecstasy)

3,4-Methylenedioxymethamphetamine (MDMA), commonly referred to as Ecstasy, is a widely abused, psychoactive recreational drug, which induces short- and long-term neuropsychiatric behaviors. This drug is neurotoxic to serotonergic neurons in vivo, and induces programmed cell death in cultured human serotonergic cells and rat neocortical neurons. Over the years it has been shown that MDMA alters the release of several neurotransmitters in the brain, it induces recompartmentation of intracellular serotonin and c-fos, and modifies the expression of a few genes. Recently, we observed changes in gene expression in mice treated with MDMA, and cloned and sequenced 11 cDNAs thus affected (4 correspond to known and 7 to unknown genes). The effect of MDMA on two of these genes, GABA transporter 1 and synaptotagmin IV was studied in detail. Characterization of the relationship between a given gene and certain physiological or behavioral effects of MDMA could shed light on the mechanism of the drug's action. However, establishing such a connection is difficult for several reasons, including that serotonergic neurons are not the only cells affected by MDMA. In this review, molecular and neurochemical events that occur in the brain following exposure to MDMA, and link between the observed molecular changes with known physiological effects of the drug are discussed. It is indicated that MDMA alters the expression of several proteins involved in GABA neurotransmission, thus having critical effect on thermoregulation and MDMA acute toxicity. This analysis should facilitate development of novel approaches to prevent deleterious effects, especially mortality induced by MDMA and other abused psychostimulants.

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.

Analysis of ecstasy (MDMA)-induced transcriptional responses in the rat cortex

3,4-methylenedioxymethamphetamine (MDMA, ecstasy) is a popular drug of abuse. MDMA is pharmacologically classified as an entactogen because of its affinities to classical hallucinogens and stimulants. Oral ingestion of a single dose of the drug is associated with euphoria, elevated self-confidence, and heightened sensory awareness in humans. Evidence for neurotoxicity in the human serotonin (5-HT) system has been provided. In rats, a single injection of MDMA induces hyperthermia and formation of reactive oxygen species. These effects may cause MDMA-associated, long-term 5-HT depletion, with the cortex being quite sensitive to the biochemical effects of MDMA. It has been suggested that these MDMA effects may be associated with molecular changes in this brain region. To test these ideas, we have made use of the cDNA array analysis, which can provide a more global view of the molecular changes secondary to MDMA injections. Our results show that the genes regulated by MDMA encode proteins that belong to signaling pathways, transcription regulators, or xenobiotic metabolism. Our observations indicate that cortical cells respond to the acute administration of MDMA by modulating transcription of several genes that might lead to long-term changes in the brain.

Studies, using in vivo microdialysis, on the effect of the dopamine uptake inhibitor GBR 12909 on 3,4-methylenedioxymethamphetamine ('ecstasy')-induced dopamine release and free radical formation in the mouse striatum

The present study examined the mechanisms by which 3,4-methylenedioxymethamphetamine (MDMA) produces long-term neurotoxicity of striatal dopamine neurones in mice and the protective action of the dopamine uptake inhibitor GBR 12909. MDMA (30 mg/kg, i.p.), given three times at 3-h intervals, produced a rapid increase in striatal dopamine release measured by in vivo microdialysis (maximum increase to 380 +/- 64% of baseline). This increase was enhanced to 576 +/- 109% of baseline by GBR 12909 (10 mg/kg, i.p.) administered 30 min before each dose of MDMA, supporting the contention that MDMA enters the terminal by diffusion and not via the dopamine uptake site. This, in addition to the fact that perfusion of the probe with a low Ca(2+) medium inhibited the MDMA-induced increase in extracellular dopamine, indicates that the neurotransmitter may be released by a Ca(2+) -dependent mechanism not related to the dopamine transporter. MDMA (30 mg/kg x 3) increased the formation of 2,3-dihydroxybenzoic acid (2,3-DHBA) from salicylic acid perfused through a probe implanted in the striatum, indicating that MDMA increased free radical formation. GBR 12909 pre-treatment attenuated the MDMA-induced increase in 2,3-DHBA formation by approximately 50%, but had no significant intrinsic radical trapping activity. MDMA administration increased lipid peroxidation in striatal synaptosomes, an effect reduced by approximately 60% by GBR 12909 pre-treatment. GBR 12909 did not modify the MDMA-induced changes in body temperature. These data suggest that MDMA-induced toxicity of dopamine neurones in mice results from free radical formation which in turn induces an oxidative stress process. The data also indicate that the free radical formation is probably not associated with the MDMA-induced dopamine release and that MDMA does not induce dopamine release via an action at the dopamine transporter.

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.

The effect of (R)-HA966 or ACEA 1021 on dexfenfluramine or (S)-MDMA-induced changes in temperature, activity, and neurotoxicity

The glycine site-specific N-methyl-D-aspartate (NMDA) antagonist 5-nitro-6,7-dichloro-2,3-quinoxalinedione (ACEA 1021, 4x30 mg/kg, i.p.) given 30 min before dexfenfluramine (4x15 mg/kg, i.p., every 2 h) was unable to prevent dexfenfluramine-induced depletion of 5-hydroxytryptamine (5-HT), 5-hydroxyindoleacetic acid (5-HIAA) content, and 5-HT transporter (5-HTT) density. Another glycine site-specific NMDA antagonist, R(+)-3-aminohydroxypyrrolidin-2-one [(R)-HA 966] (2x30 mg/kg, ip), given 30 min before dexfenfluramine (2x10 mg/kg, ip, 2 hourly) was also unable to prevent regional depletion of 5-HT, 5-HIAA, and 5-HTT density. However, ACEA 1021 (4x30 mg/kg, i.p.) given 30 min before (S)-3,4-methylenedioxymethamphetamine (MDMA, 4x10 mg/kg, 2 hourly, ip) attenuated the regional depletion of dopamine (DA), dihydroxyphenylacetic acid (DOPAC), 5-HT, 5-HIAA content, and 5-HTT density. ACEA 1021 combined with (S)-MDMA also prevented (S)-MDMA-induced hyperthermia without causing hypothermia or preventing an (S)-MDMA-induced increase in locomotor activity.

Effect of GBR 12909 and fluoxetine on the acute and long term changes induced by MDMA ('ecstasy') on the 5-HT and dopamine concentrations in mouse brain

We examined the long term effect of 3,4 methylenedioxymethamphetamine (MDMA, 10, 20 and 30 mg/kg, i.p.) on the cerebral 5-hydroxytryptamine (5-HT) and dopamine content in Swiss Webster mice. Three injections of MDMA (20 or 30 mg/kg, i.p.) given 3 h apart produced a marked depletion in the striatal content of dopamine and its metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) 7 days later. None of the doses administered altered the concentration of 5-HT or its metabolite 5-hydroxyindoleacetic acid (5-HIAA) in several brain areas. Pre-treatment with the dopamine uptake inhibitor GBR 12909 (10 mg/kg, i.p.), 30 min before each of the three MDMA (30 mg/kg, i.p.) injections, completely prevented the long term loss in the striatal catechol concentrations. However, GBR 12909 (10 mg/kg, i.p.) not only failed to prevent the acute effects induced by MDMA (30 mg/kg x 3, i.p.) on dopamine metabolism 30 min later, but in fact potentiated them. The 5-HT uptake inhibitor, fluoxetine (10 mg/kg, i. p.) failed to prevent both the acute and long term dopaminergic deficits. MDMA (30 mg/kg x 3) altered the body temperature of the mice biphasically, producing a rapid hyperthermia followed by prolonged hypothermia. In contrast, MDMA (20 mg/kg x 3) produced an initial hypothermia followed by hyperthermia. The present experiments therefore appear to rule out any direct relationship between the neurotoxic effects of MDMA and its acute effects on body temperature in mice. Fluoxetine administered 30 min before each MDMA (30 mg/kg) injection prevented these temperature changes, while GBR 12909 was without effect. This suggests that the neuroprotective effect of GBR 12909 against MDMA-induced neurotoxicity is not directly related to its ability to inhibit the MDMA-induced acute effects on dopamine metabolism or alter the MDMA-induced temperature change. The data illustrate major differences in the neurotoxic profile of MDMA in mice and rats.

Effect of ecstasy [3,4-methylenedioxymethamphetamine (MDMA)] on cerebral blood flow: a co-registered SPECT and MRI study

3,4-methylenedioxymethamphetamine (MDMA), an illicit recreational drug, damages serotonergic nerve endings. Since the cerebrovasculature is regulated partly by the serotonergic system, MDMA may affect cerebral blood flow (CBF) in humans. We evaluated 21 abstinent recreational MDMA users and 21 age- and gender-matched healthy subjects with brain SPECT and MRI. Ten of the MDMA subjects also had repeat SPECT and MRI after receiving two doses of MDMA. Abstinent MDMA users showed no significantly different global or regional CBF (rCBF) compared to the control subjects. However, within 3 weeks after MDMA administration, rCBF remained decreased in the visual cortex, the caudate, the superior parietal and dorsolateral frontal regions compared to baseline rCBF. The decreased rCBF tended to be more pronounced in subjects who received the higher dosage of MDMA. Two subjects who were scanned at 2-3 months after MDMA administration showed increased rather than decreased rCBF. Low-dose recreational MDMA use does not cause detectable persistent rCBF changes in humans. The lack of long-term rCBF changes may be due to a non-significant effect of serotonergic deficits on rCBF, or regeneration of serotonergic nerve terminals. The subacute decrease in rCBF after MDMA administration may be due to the direct effect of MDMA on the serotonergic system or the indirect effects of its metabolites on the dopaminergic system; the preliminary data suggest these effects may be transient.

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.

Studies on the role of dopamine in the degeneration of 5-HT nerve endings in the brain of Dark Agouti rats following 3,4-methylenedioxymethamphetamine (MDMA or 'ecstasy') administration

1. We investigated whether dopamine plays a role in the neurodegeneration of 5-hydroxytryptamine (5-HT) nerve endings occurring in Dark Agouti rat brain after 3,4-methylenedioxymethamphetamine (MDMA or 'ecstasy') administration. 2. Haloperidol (2 mg kg(-1) i.p.) injected 5 min prior and 55 min post MDMA (15 mg kg(-1) i.p.) abolished the acute MDMA-induced hyperthermia and attenuated the neurotoxic loss of 5-HT 7 days later. When the rectal temperature of MDMA + haloperidol treated rats was kept elevated, this protective effect was marginal. 3. MDMA (15 mg kg(-1)) increased the dopamine concentration in the dialysate from a striatal microdialysis probe by 800%. L-DOPA (25 mg kg(-1) i.p., plus benserazide, 6.25 mg kg(-1) i.p.) injected 2 h after MDMA (15 mg kg(-1)) enhanced the increase in dopamine in the dialysate, but subsequent neurodegeneration was unaltered. L-DOPA (25 mg kg(-1)) injected before a sub-toxic dose of MDMA (5 mg kg(-1)) failed to induce neurodegeneration. 4. The MDMA-induced increase in free radical formation in the hippocampus (indicated by increased 2,3- and 2,5-dihydroxybenzoic acid in a microdialysis probe perfused with salicylic acid) was unaltered by L-DOPA. 5. The neuroprotective drug clomethiazole (50 mg kg(-1) i.p.) did not influence the MDMA-induced increase in extracellular dopamine. 6. These data suggest that previous observations on the protective effect of haloperidol and potentiating effect of L-DOPA on MDMA-induced neurodegeneration may have resulted from effects on MDMA-induced hyperthermia. 7. The increased extracellular dopamine concentration following MDMA may result from effects of MDMA on dopamine re-uptake, monoamine oxidase and 5-HT release rather than an 'amphetamine-like' action on dopamine release, thus explaining why the drug does not induce degeneration of dopamine nerve endings.

The relationship between the degree of neurodegeneration of rat brain 5-HT nerve terminals and the dose and frequency of administration of MDMA ('ecstasy')

The effect of varying the dose and frequency of administration of 3,4-methylenedioxymethamphetamine (MDMA or 'ecstasy') on both the acute hyperthermic response and the long term neurodegeneration of 5-hydroxytryptamine (5-HT) nerve terminals in the brain has been studied in Dark Agouti rats. A single injection (4-15 mg/kg i.p.) of MDMA produced immediate dose-related hyperthermia and a dose-related decrease in 5-HT, 5-hydroxyindoleacetic acid (5-HIAA) and [3H]paroxetine binding in regions of the brain 7 days later, with a dose of 4 mg/kg having no degenerative effect. This dose was also without effect when given once daily for 4 days, but produced a marked loss of [3H]paroxetine binding and indole concentration ( approximately 55%) when given twice daily for 4 days. When a dose of 4 mg/kg was given twice weekly for 8 weeks it had no effect on these serotoninergic markers, despite a clear anorectic effect of the drug being seen. These data demonstrate that MDMA-induced neurodegeneration is related to both the dose and frequency of administration and indicate that damage to 5-HT neurones can occur in the absence of a hyperthermic response to the drug. We suggest that damage occurs when endogenous free radical scavenging mechanisms become overwhelmed or exhausted.

MDMA ('Ecstasy') enhances 5-HT1A receptor density and 8-OH-DPAT-induced hypothermia: blockade by drugs preventing 5-hydroxytryptamine depletion

One week after a single administration of 3,4-methylenedioxymethamphetamine (MDMA HCI, 30 mg/kg i.p.), 5-HT1A receptor density was significantly increased by approximately 25-30% in the frontal cortex and hypothalamus of rats. The increased density correlated with the potentiation of the hypothermic response to the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT, 1 mg/kg s.c.). Hypothalamic 5-HT7 receptors, which also bind 8-OH-DPAT, were not changed, however, by MDMA. Fluoxetine (5 mg/kg s.c.), ketanserin (5 mg/kg s.c.) or haloperidol (2 mg/kg i.p.), given 15 min prior to MDMA, prevented the depletion of 5-hydroxytryptamine (5-HT) induced by MDMA and also blocked the effects of this neurotoxin on 5-HT1A receptor density and on 8-OH-DPAT-induced hypothermia. The protection afforded by drugs against 5-HT loss did not correlate, however, with the antagonism of the acute hyperthermic effect of MDMA. The present results indicate that drugs able to prevent or to attenuate MDMA-induced 5-HT loss also prevent the changes in 5-HT1A receptor density as well as the enhanced hypothermic response to the 5-HT1A receptor agonist 8-OH-DPAT in MDMA-treated rats.

Why tryptophan hydroxylase is difficult to purify: a reactive oxygen-derived species-mediated phenomenon that may be implicated in human pathology

1. Attempts and apparently successful procedures to obtain reasonable quantities of electrophoretically homogenous mammalian brain-derived tryptophan hydroxylase, (TPH), have been described, starting in the early 1970s. This work has been carried out with the primary objective to obtain specific antisera to this enzyme to map out serotonergic pathways in the nervous system. 2. By using a multitude of techniques, antisera have indeed been fabricated and employed. However, it is doubtful if pure, native TPH has ever been produced. Indeed, there is strong evidence that more than one isoform of TPH exists in the rat brain. Thus, these antisera are probably directed against TPH-derived polypeptides and not the holoenzyme(s). 3. The difficulty in the purification of TPH lies not only in its subjectivity to proteolysis, but more importantly in its probable capacity to produce superoxide leading to hydrogen perioxide formation. This, in turn, may undergo Fenton chemistry with iron at the active site of the protein to produce hydroxyl radicals that directly attack and destroy the enzyme molecule. Evidence for such a mechanism is presented together with possible protocols that might be used to produce pure stable holo TPH(s). 4. It is hypothesized that similar oxidative events may take place in vivo under certain conditions leading to pathological results. Strategies to block these events are suggested.

Causes and consequences of the loss of serotonergic presynapses elicited by the consumption of 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy") and its congeners

The massive and prolonged stimulation of serotonin (5-HT)-release and the increased dopaminergic activity are responsible for the acute psychomimetic and psychostimulatory effects of 3,4-methylenedioxy-methamphetamine (MDMA, "ecstasy") and its congeners. In vulnerable subjects, at high doses or repeated use, and under certain unfavorable conditions (crowding, high ambient temperature), severe, in some cases fatal, averse systemic reactions (hyperthermia, serotonin-syndrome) may occur during the first few hours. Animal experiments revealed the existence of similar differences in vulnerability and similar dose- and context-related influences on a similar sequence of acute responses. The severity of these acute systemic responses is closely related to the severity of the long-term damage to 5-HT axon terminals caused by the administration of substituted amphetamines. Attempts to identify the mechanisms involved in this selective degeneration of 5-HT presynapses brought to light a multitude of different factors and conditions which either attenuate or potentiate the loss of 5-HT terminals caused by MDMA and related amphetamine derivatives. These puzzling observations suggest that the degeneration of 5-HT presynapses represents only the final step in a sequence of events which compromise the ability of 5-HT terminals to maintain their functional and structural integrity. Substituted amphetamines selectively tax energy metabolism in 5-HT presynapses through their ability to exchange with 5-HT and to dissipate transmembrane ion gradients. The active carrier systems in the vesicular and presynaptic membrane operate at a permanently activated state. The resulting energy deficit can no longer adequately restored by the 5-HT presynapses when their availability of substrates for ATP production is additionally reduced by the hyperthermic and other energy consuming reactions which are elicited by the systemic administration of substituted amphetamines. The exhaustion of energy in 5-HT nerve terminals compromised all energy-requiring endogenous mechanisms involved in the regulation of transmembrane-ion exchange, internal Ca(++)-homeostasis, prevention of oxidative stress, detoxification, and repair. Above a critical threshold the failure of these self-protective mechanisms will lead to the degeneration of the 5-HT axon terminals. Based on the role of 5-HT as a global modulatory transmitter-system involved in the stabilization and integration of impulse flow between distributed multifocal neuronal networks, the partial loss of 5-HT presynapses must be expected to impair the ability of these networks to maintain the integrity of signal flow pattern, and increase the likelihood of switching to unstable information processing. Behavioral responding may therefore become more dominated by activities generated in individual networks, and hitherto "buffered" personality traits and predisposition may become manifested as defined psychiatric syndromes in certain predisposed subjects.

In vivo evidence for free radical involvement in the degeneration of rat brain 5-HT following administration of MDMA ('ecstasy') and p-chloroamphetamine but not the degeneration following fenfluramine

1. Administration of 3,4-methylenedioxymethamphetamine (MDMA or 'ecstasy') to several species results in a long lasting neurotoxic degeneration of 5-hydroxytryptaminergic neurones in several regions of the brain. We have now investigated whether this degeneration is likely to be the result of free radical-induced damage. 2. Free radical formation can be assessed by measuring the formation of 2,3- and 2,5-dihydroxybenzoic acid (2,3-DHBA and 2,5-DHBA) from salicylic acid. An existing method involving implantation of a probe into the hippocampus and in vivo microdialysis was modified and validated. 3. Administration of MDMA (15 mg kg-1, i.p.) to Dark Agouti (DA) rats increased the formation of 2,3-DHBA (but not 2,5-DHBA) for at least 6 h. Seven days after this dose of MDMA, the concentration of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) was reduced by over 50% in hippocampus, cortex and striatum, reflecting neurotoxic damage. There was no change in the concentration of dopamine or 3,4-dihydroxyphenylacetic acid (DOPAC) in the striatum. 4. p-Chloroamphetamine (PCA), another compound which produces a neurotoxic loss of cerebral 5-HT content, when given at a dose of 5 mg kg-1 also significantly increased the formation of 2.3-DHBA (but not 2,5-DHBA) in the dialysate for over 4.5 h. post-injection starting 2 h after treatment. 5. In contrast, fenfluramine administration (15 mg kg-1, i.p.) failed to increase the 2,3-DHBA or 2,5-DHBA concentration in the dialysate. A single fenfluramine injection nevertheless also markedly decreased the concentration of 5-HT and 5-HIAA in the hippocampus, cortex and striatum seven days later. 6. When rats pretreated with fenfluramine (15 mg kg-1, i.p.) seven days earlier were given MDMA (15 mg kg-1, i.p.) no increase in 2,3-DHBA was seen in the dialysate from the hippocampal probe. This indicates that the increase in free radical formation following MDMA is occurring in 5-HT neurones which have been damaged by the prior fenfluramine injection. 7. Administration of the free radical scavenging agent alpha-phenyl-N-tert-butyl nitrone (PBN; 120 mg kg-1, i.p.) 10 min before and 120 min after an MDMA (15 mg kg-1, i.p.) injection prevented the acute rise in the 2,3-DHBA concentration in the dialysate and attenuated by 30% the long term damage to hippocampal 5-HT neurones (as indicated by a smaller MDMA-induced decrease in both the concentration of 5-HT and 5-HIAA and also the binding of [3H]-paroxetine). 8. These data indicate that a major mechanism by which MDMA and PCA induce damage to 5-hydroxytryptaminergic neurones in rat brain is by increasing the formation of free radicals. These probably result from the degradation of catechol and quinone metabolites of these substituted amphetamines. In contrast, fenfluramine induces damage by another mechanism not involving free radicals; a proposal supported by some of our earlier indirect studies. 9. We suggest that these different modes of action render untenable the recent suggestion that MDMA will not be neurotoxic in humans because fenfluramine appears safe at clinical doses.

A study of the neurotoxic effect of MDMA ('ecstasy') on 5-HT neurones in the brains of mothers and neonates following administration of the drug during pregnancy

1. It is well established that 3,4-methylenedioxymethamphetamine (MDMA or 'ecstasy') is neurotoxic and produces long term degeneration of cerebral 5-hydroxytryptamine (5-HT) nerve terminals in many species. Since MDMA is used extensively as a recreational drug by young people, it is being ingested by many women of child bearing age. We have therefore examined the effect of administering high doses of MDMA to rats during pregnancy on the cerebral content of both the dams and the neonates. 2. MDMA (20 mg kg-1, s.c.) was injected twice daily on days 14-17 of the gestation period. The initial dose produced a marked hyperthermic response in the dam which was progressively attenuated in both peak height and area under the curve following further doses of the drug. The body weight of the dams decreased during the period of treatment. 3. There was a modest decrease in litter size (-20%) of the MDMA-treated dams. 4. The concentration of 5-HT and its metabolite 5-HIAA was decreased by over 65% in the hippocampus and striatum and 40% in the cortex of the dams 1 week after parturition. In contrast, the content of 5-HT and 5-HIAA in the dorsal telencephalon of the pups of the MDMA-treated dams was the same as that seen in tissue from pups born to control animals. 5. Administration of MDMA (40 mg kg-1, s.c.) to adult rats increased thiobarbituric acid reacting substances (TBARS) in cortical tissue 3 h and 6 h later, indicating increased lipid peroxidation. No increase in TBARS was seen in the cortical tissue of 7-10 day neonates injected with this dose of MDMA 3 h or 6 h earlier. 6. The data suggest that exposure to MDMA in utero during the maturation phase does not produce damage to 5-HT nerve terminals in the foetal rat brain, in contrast to the damage seen in the brains of the mothers. This may be due to MDMA being metabolized to free radical producing entities in the adult brain but not in the immature brain or, alternatively, to more effective or more active free radical scavenging mechanisms being present in the immature brain.

Are the reactive oxygen-derived species (ROS) interactive properties of the many therapeutic drugs from various categories pertinent to their beneficial effects?

Many pathologic states are known to involve the generation of reactive oxygen species, (ROS). It is not known at present to what extent these phenomena are due to ROS formation, or if their formation is a result of the disease. Many therapeutic drugs either scavenge ROS or inhibit their formation. The purpose of this review is to match the drugs used for certain diseases with their anti-ROS actions. This attempted correlation is made to try to give an answer to the title question.

What is the role of the gamma-hydroxybutyrate receptor?

A possible functional role for endogenous gamma-hydroxybutyrate has been disputed. However, there are receptor sites for this molecule, which are highly enriched in the synaptosomal membrane fraction in the rat brain and are functionally linked to a guanosine triphosphate-binding protein. These data suggest that they play a neurological role. The binding sites recognize some drug molecules that bear no structural similarity to gamma-hydroxybutyrate. Recent experimental evidence indicates the existence of endogenous hydrophobic ligands. As a minor brain metabolite directly or indirectly involved in scavenging oxygen-derived free radicals, gamma-hydroxybutyrate demonstrates similarities with melatonin. The gamma-hydroxybutyrate receptor is compared to the cannabis receptor, for which an endogenous hydrophobic ligand has been identified. Structurally similar molecules to this ligand are believed to be implicated in the sleep process. As gamma-hydroxybutyrate itself can induce sleep, a search amongst these molecules as possible ligands for the gamma-hydroxybutyrate receptor might be enlightening.

Studies on the mechanism of p-chloroamphetamine neurotoxicity

Studies were conducted to investigate the sensitivity of p-chloroamphetamine (PCA)-induced neurochemical changes to various pharmacological manipulations known to block the neurochemical effects of 3,4-methylenedioxymethamphetamine (MDMA). The monoamine oxidase-B (MAO-B) inhibitor L-deprenyl (2 mg/kg) given 4 hr before a nonneurotoxic dose of PCA (2 mg/kg) was shown not to alter the amount of [3H]paroxetine bound to serotonin (5-HT) uptake sites 7 days after treatment. L-Deprenyl 4 hr before a neurotoxic dose of PCA (10 mg/kg) did not change the acute hyperthermia. Further, neither L-deprenyl nor another selective MAO-B inhibitor, MDL-72,974 (1.25 mg/kg), given 30 min before or daily for 4 days before a single dose of PCA attenuated or potentiated the decrease in the number of [3H]paroxetine binding sites measured 7 days after PCA treatment. The combination of the MAO-A inhibitor clorgyline (2.5 mg/kg) or a nonspecific dose of L-deprenyl (10 mg/kg) with the selective 5-HT releasing agent 5,6-methylenedioxy-2-aminoindan did not lead to changes in the levels of 5-HT, 5-hydroxyindoleacetic acid or dopamine 7 days after treatment. Finally, the 5-HT2A receptor antagonist MDL-11,939 (5 mg/kg) did not protect against the neurotoxicity of PCA. By comparing the present work with previous studies of MDMA, these results can be interpreted to suggest that the mechanism of the neurotoxicity induced by PCA is not identical to that induced by MDMA. The relationship of these results to the neurotoxicity induced by MDMA is also discussed.

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.

The spin trap reagent alpha-phenyl-N-tert-butyl nitrone prevents 'ecstasy'-induced neurodegeneration of 5-hydroxytryptamine neurones

Administration of a single dose (10 mg/kg i.p.) of 3,4-methylenedioxy-methamphetamine (MDMA or 'ecstasy') produced a 40% loss of 5-hydroxytryptamine (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) in cortex and hippocampus of Dark Agouti rats 7 days later. Binding of [3H]paroxetine to the presynaptic 5-HT nerve terminals in cortex was decreased by approximately 30%. Injection of the spin trap reagent alpha-phenyl-N-tert-butyl nitrone (PBN; 150 mg/kg i.p.) 10 min prior and 120 min post MDMA administration totally prevented the loss in [3H]paroxetine binding in the cortex and attenuated the loss of 5-HT and 5-HIAA in both brain regions. PBN alone had no effect on [3H]paroxetine binding or brain 5-HT content. These data suggest that MDMA produces neurodegeneration of 5-HT neurones because of reactive free radical formation.

Review of the pharmacology and clinical pharmacology of 3,4-methylenedioxymethamphetamine (MDMA or "Ecstasy")

3,4-Methylenedioxymethamphetamine (MDMA or "Ecstasy") was first synthesised 80 years ago, but has recently received prominence as an illegally synthesised recreational drug of abuse. There is a widely held belief among misusers that it is safe. In the last 2-3 years there have been a number of reports of the drug producing severe acute toxicity and death and there are concerns that it may cause long term toxic damage to 5-hydroxytryptamine (5-HT) nerve terminals. There is a considerable literature on the acute pharmacological effects of MDMA in experimental animals, and this is reviewed. The drug produces both hyperthermia and the "serotonin syndrome", a series of behavioural changes which result from increased 5-HT function. Acute clinical toxicity problems following MDMA ingestion also include hyperthermia and the appearance of the serotonin syndrome. The hyperthermia appears to precipitate other severe clinical problems and the outcome can be fatal. In agreement with others, we suggest that the recent increase in the number of reports of MDMA toxicity probably results from the widespread use of the drug at all night dance parties or "raves". The phenomenon of amphetamine aggregation toxicity in mice was reported 40 years ago. If applicable to MDMA-induced toxicity in humans, all the conditions necessary to induce or enhance toxicity are present at raves: crowded conditions (aggregation), high ambient temperature, loud noise and dehydrated subjects. Administration of MDMA to rodents and non-human primates results in a long term neurotoxic decrease in 5-HT content in several brain regions and there is clear biochemical and histological evidence that this reflects neurodegeneration of 5-HT terminals. Unequivocal data demonstrating that similar changes occur in human brain do not exist, but limited and indirect clinical evidence gives grounds for concern. There are also data suggesting that long term psychiatric changes can occur, although there are problems of interpretation and these are reviewed. Suggestions for the rational treatment of the acute toxicity are made on the basis of both pharmacological studies in animals and current clinical practice. Cases presenting clinically are usually emergencies and unlikely to allow carefully controlled studies. Proposals include decreasing body temperature (possibly with ice), the use of dantrolene and anticonvulsant and sedative medication, particularly benzodiazepines. The use of neuroleptics requires care because of the theoretical risk of producing the neuroleptic malignant syndrome and the possibility of precipitating seizures. In rats, chlormethiazole antagonises the hyperthermia produced by MDMA and has been shown clinically to block MDMA-induced convulsive activity.

Chlormethiazole and dizocilpine block the behavioural, but not the neurotoxic effects of 5,7-dihydroxytryptamine in mice

Intracerebroventricular administration to mice of 5,7-dihydroxytryptamine at a dose of 300 micrograms resulted in convulsive behaviour and death (latency 7.6 +/- 1.7 min.). Pretreatment with dizocilpine or chlormethiazole resulted in a dose dependent inhibition of the convulsive behaviour. A dose of dizocilpine of 0.12 mumol/kg or chlormethiazole at a dose of 150 mumol/kg prevented seizures for 30 min. Injection of 5,7-dihydroxytryptamine (75 micrograms, intracerebroventricularly) produced an approximate 50% neurotoxic loss of cerebral 5-hydroxytryptamine (5-HT) and its metabolite 5-hydroxyindole acetic acid (5-HIAA) 8 days later. This loss was not prevented by administration of either dizocilpine (4.5 mumol/kg intraperitoneally) or chlormethiazole (300 mumol/kg intraperitoneally) given 5 min. before and 55 min. after the 5,7-dihydroxytryptamine injection. It is proposed that chlormethiazole and dizocilpine may protect against 5,7-dihydroxytryptamine-induced seizures because of their anticonvulsant activity, but that they do not prevent the neurotoxic effects of the compound. The data also suggest that the neurotoxic effects of substituted amphetamines such as 3,4-methylene dioxymethamphetamine (MDMA or Ecstasy) do not result from the formation of a 5,7-dihydroxytryptamine like compound.