Serotonergic neurotoxicity of MDMA (ecstasy) in the developing rat brain

Developmental neurotoxicity of MDMA. A systematic literature review summarized in a putative adverse outcome pathway

The increasing use of illegal drugs by pregnant women causes a public health concern because it is associated with health risks for mothers and their developing children. One of such drugs is MDMA (3,4-methylenedioxymethamphetamine) or ecstasy due to its high consumption in relevant age and sex groups and its adverse effects on human and rodent developing brains. To thoroughly review the current knowledge on the developmentally neurotoxic potential of MDMA we systematically collected and summarized articles investigating developmental neurotoxicity (DNT) of MDMA in humans and animals in vivo and in vitro. In addition, we summarized the findings in a putative adverse outcome pathway (AOP). From an initial 299 articles retrieved from the bibliographic databases Web of Science, PubMed and DART, we selected 39 articles according to inclusion/exclusion criteria for data collection after title/abstract and full text screening. Of these 3 where epidemiological studies, 34 where in vivo studies in mice and rats and 2 were in vitro studies. The three epidemiological studies reported from the same longitudinal study and suggested that MDMA exposure during pregnancy impairs neuromotor function in infants. In rat, postnatal exposure towards MDMA also caused locomotor deficits as well as impaired spatial learning that might be associated with decreased serotonin levels in the hippocampus. In vitro MDMA caused cytotoxicity at high concentrations and effects on the serotonergic and neuritogenic alterations at lower concentrations which are in line with some of the in vivo alterations observed. Considering the adverse outcomes of developmental MDMA described in humans and in rodents we summarized the first putative AOP on developmental compound exposure leading to impaired neuromotor function in children. For generation of this AOP, MDMA exposure was taken as a model compound. In addition, we hypothesized a second AOP involving developmental disturbance of the dopaminergic system. However, further in vitro mechanistic studies are needed to understand the molecular initiating event(s) (MIE) triggering the downstream cascades and obtain consistent evidences causally linking the adverse outcome to effects at the cellular, organ and organism level.

The effects of ecstasy on neurotransmitter systems: a review on the findings of molecular imaging studies

RATIONALE

Ecstasy is a commonly used psychoactive drug with 3,4-methylenedioxymethamphetamine (MDMA) as the main content. Importantly, it has been suggested that use of MDMA may be neurotoxic particularly for serotonergic (5-hydroxytryptamine (5-HT)) neurons. In the past decades, several molecular imaging studies examined directly in vivo the effects of ecstasy/MDMA on neurotransmitter systems.

OBJECTIVES

The objective of the present study is to review the effects of ecstasy/MDMA on neurotransmitter systems as assessed by molecular imaging studies in small animals, non-human primates and humans.

METHODS

A search in PubMed was performed. Eighty-eight articles were found on which inclusion and exclusion criteria were applied.

RESULTS

Thirty-three studies met the inclusion criteria; all were focused on the 5-HT or dopamine (DA) system. Importantly, 9 out of 11 of the animal studies that examined the effects of MDMA on 5-HT transporter (SERT) availability showed a significant loss of binding potential. In human studies, this was the case for 14 out of 16 studies, particularly in heavy users. In abstinent users, significant recovery of SERT binding was found over time. Most imaging studies in humans that focused on the DA system did not find any significant effect of ecstasy/MDMA use.

CONCLUSIONS

Preclinical and clinical molecular imaging studies on the effects of ecstasy/MDMA use/administration on neurotransmitter systems show quite consistent alterations of the 5-HT system. Particularly, in human studies, loss of SERT binding was observed in heavy ecstasy users, which might reflect 5-HT neurotoxicity, although alternative explanations (e.g. down-regulation of the SERT) cannot be excluded.

The effects of ecstasy (MDMA) on brain serotonin transporters are dependent on age-of-first exposure in recreational users and animals

Rationale and Objective

Little is known on the effects of ecstasy (MDMA, a potent 5-HT-releaser and neurotoxin) exposure on brain development in teenagers. The objective of this study was to investigate whether in humans, like previous observations made in animals, the effects of MDMA on the 5-HT system are dependent on age-of-first exposure.

Methods

5-HT transporter (SERT) densities in the frontal cortex and midbrain were assessed with [¹²³I]β-CIT single photon emission computed tomography in 33 users of ecstasy. Subjects were stratified for early-exposed users (age-at-first exposure 14–18 years; developing brain), and late-exposed users (age-at-first exposure 18–36 years; mature brain). In parallel, we investigated the effects of age experimentally with MDMA in early-exposed (adolescent) rats and late-exposed (adult) rats using the same radioligand.

Results

On average, five years after first exposure, we found a strong inverse relationship, wherein age-at-first exposure predicted 79% of the midbrain SERT variability in early (developing brain) exposed ecstasy users, whereas this was only 0.3% in late (mature brain) exposed users (p = 0.007). No such effect was observed in the frontal cortex. In rats, a significant age-BY-treatment effect (p<0.01) was observed as well, however only in the frontal cortex.

Conclusions

These age-related effects most likely reflect differences in the maturational stage of the 5-HT projection fields at age-at-first exposure and enhanced outgrowth of the 5-HT system due to 5-HT’s neurotrophic effects. Ultimately, our findings stress the need for more knowledge on the effects of pharmacotherapies that alter brain 5-HT levels in the pediatric population.

MDMA (ecstasy) delays pubertal development and alters sperm quality after developmental exposure in the rat

3,4-Methylenedioxymethamphetamine, MDMA or "ecstasy" is consumed mainly by young population at childbearing age. Therefore, there may be a risk of exposure of some pregnant women. The effects of the developmental exposure to MDMA on the sexual development and long-term sexual behaviour/fertility were assessed in Sprague-Dawley rats. MDMA was administered subcutaneously at 0 (control), 0.5, 5 and 10 mg/kg to female rats once a day, three consecutive days a week during 10 weeks, including gestation and lactation. The male offspring was evaluated for sexual maturation and mated with untreated sexually receptive females to evaluate the mating and pregnancy rates. Hormonal, haematological, biochemical, histological, genotoxicological and testicular and sperm parameters were also evaluated. A significant higher incidence of DNA damage in sperm and interstitial oedema in testes was found. There was also a significant and dose-related decrease in sperm count and a significant decrease in sperm motility at all doses. A significant delay in preputial separation onset in all treated groups was observed. This study reports by the first time an alteration of spermatogenesis after in utero and lactation MDMA exposure in the rat.

(+/-)3,4-Methylenedioxymethamphetamine (MDMA) dose-dependently impairs spatial learning in the morris water maze after exposure of rats to different five-day intervals from birth to postnatal day twenty

During postnatal days (PD) 11-20, (+/-)3,4-methylenedioxymethamphetamine (MDMA) treatment impairs egocentric and allocentric learning, and reduces spontaneous locomotor activity; however, it does not have these effects during PD 1-10. How the learning impairments relate to the stress hyporesponsive period (SHRP) is unknown. To test this association, the preweaning period was subdivided into 5-day periods from PD 1-20. Separate pups within each litter were injected subcutaneously with 0, 10, 15, 20, or 25 mg/kg MDMA x4/day on PD 1-5, 6-10, 11-15, or 16-20, and tested as adults. The 3 highest MDMA dose groups showed reduced locomotor activity during the first 10 min (of 60 min), especially in the PD 1-5 and 6-10 dosing regimens. MDMA groups in all dosing regimens showed impaired allocentric learning in the Morris water maze (on acquisition and reversal, all MDMA groups were affected; on the small platform phase, the 2 high-dose groups were affected). No effects of MDMA were found on anxiety (elevated zero maze), novel object recognition, or egocentric learning (although a nonsignificant trend was observed). The Morris maze results did not support the idea that the SHRP is critical to the effects of MDMA on allocentric learning. However, since no effects on egocentric learning were found, but were apparent after PD 11-20 treatment, the results show that these 2 forms of learning have different exposure-duration sensitivities.

Developmental effects of 3,4-methylenedioxymethamphetamine: a review

+/-3,4-Methylenedioxymethamphetamine (MDMA) is a chemical derivative of amphetamine that has become a popular drug of abuse and has been shown to deplete serotonin in the brains of users and animals exposed to it. To date, most studies have investigated the effects of MDMA on adult animals. With a majority of users of MDMA being young adults, the chances of the users becoming pregnant and exposing the fetuses to MDMA are also a concern. Evidence to date has shown that developmental exposure to MDMA results in learning and memory impairments in the Morris water maze, a task known to be sensitive to hippocampal disruption, when the animals are tested as adults. Developmental MDMA exposure leads to hypoactivity in the offspring as adults but does not affect outcome on tests of anxiety. MDMA administration decreases pup weight, increases corticosterone and brain-derived neurotrophic factor levels during treatment while decreasing brain levels of serotonin; a decrease that initially dissipates and then reappears in adulthood. Neonatal MDMA exposure increases the sensitivity of the serotonin 1A receptor, a possible mechanism underlying the learning and memory deficits seen. Taken together, the evidence shows that MDMA exposure has adverse effects on the developing brain and behavior. The animal and human data on developmental MDMA exposure are reviewed and their public health implications discussed.

Developmental effects of +/-3,4-methylenedioxymethamphetamine on spatial versus path integration learning: effects of dose distribution

We previously demonstrated that postnatal day 11-20 +/-3,4-methylenedioxymethamphetamine (MDMA) exposure reduces locomotor activity and impairs path integration and spatial learning independent of the effects on activity. The effects were seen when the drug was administered twice per day, but the optimal dosing regimen is unknown. We tested whether the same total daily dose of MDMA administered in different patterns would equally affect later behavior. A split-litter design (15 litters) was used with one male/female pair per litter receiving one of four treatment regimens. All offspring received four injections per day on P11-20 as follows: 40 x 1 (40 mg/kg MDMA x 1 + saline x 3), 20 x 2 (20 mg/kg MDMA x 2 + saline x 2), 10 x 4 (10 mg/kg MDMA x 4), or Saline (saline x 4). Doses were spaced 2 h apart. Group 40 x 1 received MDMA as the first daily dose followed by three saline doses; group 20 x 2 received MDMA as the first and last dose and saline for the middle two doses; group 10 x 4 received MDMA for all four doses; and the saline group received saline for all four doses. Regardless of dose schedule, all groups treated with MDMA exhibited reduced locomotor activity. No MDMA effects were found on swimming ability in a straight channel. Modest MDMA effects were found on Barnes maze performance. The major findings were that the 40 x 1 and 20 x 2 MDMA groups showed impaired Cincinnati multiple T-water-maze learning and the 10 x 4 and 20 x 2 MDMA groups showed impaired Morris water maze learning. The results suggest that MDMA dose distribution has a long-term differential effect on different types of learning. Dose distribution warrants greater attention in the design of developmental drug studies along with the standard considerations of dose and age.

A developmental comparison of the neurobehavioral effects of ecstasy (MDMA)

The entactogen +/-3,4-methylenedioxymethamphetamine (MDMA or ecstasy) is a popular recreational drug among college, high school, and, occasionally, middle school students. Preclinical research examining the acute and long-term effects of MDMA has predominately been conducted in reproductively mature subjects but there has been increasing interest in adolescent and in utero exposure. This review examines the acute and long-term responses to MDMA during perinatal, adolescent, and adult periods. The ability of MDMA to alter core body temperature emerges gradually during ontogeny while a reduction in body weight is evident at all ages. Learning and working-memory are also altered independent of the developmental stage of exposure. Current evidence suggests adults are more sensitive to the long-term serotonin depletions following MDMA but younger ages also exhibit substantial and rapid neuroplasticity. Sexually dimorphic MDMA responses have been identified for the acute hyperthermic and motoric effects of MDMA with pubescent males being especially susceptible. Several physiological, behavioral, and neurochemical MDMA issues requiring further study are also outlined.

Neuroimaging findings with MDMA/ecstasy: technical aspects, conceptual issues and future prospects

Users of ecstasy (3,4-methylenedioxymethamphetamine; MDMA) may be at risk of developing MDMA-induced injury to the serotonin (5-HT) system. Previously, there were no methods available for directly evaluating the neurotoxic effects of MDMA in the living human brain. However, development of in vivoneuroimaging tools have begun to provide insights into the effects of ecstasy on the human brain. Single photon emission computed tomography (SPECT), positron emission computed tomography (PET) and proton magnetic resonance spectroscopy (1H-MRS) studies which have evaluated ecstasy's neurotoxic potential will be reviewed and discussed in terms of technical aspects, conceptual issues and future prospects. Although PET and SPECT may be limited by several factors such as the low cortical uptake and the use of a non-optimal reference region (cerebellum) the few studies conducted so far provide suggestive evidence that people who heavily use ecstasy are at risk of developing subcortical, and probably also cortical reductions in serotonin transporter (SERT) densities, a marker of 5-HT neurotoxicity. There seem to be dose-dependent and transient reductions in SERT for which females may be more vulnerable than males. 1H-MRS appears to be a less sensitive technique for studying ecstasy's neurotoxic potential. Whether individuals with a relatively low ecstasy exposure also demonstrate loss of SERT needs to be determined. Because most studies have had a retrospective design, in which evidence is indirect and differs in the degree to which any causal links can be implied, longitudinal studies in human ecstasy users are needed to draw definite conclusions.

3,4-Methylenedioxymethamphetamine administration on postnatal day 11 in rats increases pituitary-adrenal output and reduces striatal and hippocampal serotonin without altering SERT activity

We have previously shown that +/-3,4-methylenedioxymethamphetamine (MDMA) treatment from P11 to P20 in rats produces deficits in cognitive ability when these animals are tested in adulthood. The purpose of this experiment was to explore the neuroendocrine and neurochemical changes produced by MDMA treatment on P11. We examined monoamines in the hippocampus and striatum and the serotonin transporter in the hippocampus as well as pituitary and adrenal output following administration of MDMA (10 mg/kg, 4 times) on postnatal day 11. Significant depletions in serotonin were evident in the hippocampus 1 h and in the striatum 24 h after the first dose and remained reduced 78 h later. No changes in serotonin transporter were observed following MDMA treatment, although females had lower levels than males. No changes in dopamine were detected. The metabolites of serotonin and dopamine had different profiles than the parent compounds after MDMA administration. Plasmatic ACTH was elevated immediately following MDMA and remained elevated for at least 1 h after the last dose and returned to baseline by 24 h. Corticosterone was increased after the first dose and remained increased for at least 24 h, and returned to baseline by 30 h. The decreases in serotonin in regions important for learning and memory in conjunction with elevated levels of corticosterone during a period of stress hyporesponsiveness suggest that these initial responses to MDMA may contribute to the long-term learning and memory deficits following neonatal MDMA exposure.

Exposure to 3,4-methylenedioxymethamphetamine (MDMA) on postnatal days 11-20 induces reference but not working memory deficits in the Morris water maze in rats: implications of prior learning

3,4-methylenedioxymethamphetamine (MDMA) in previous experiments has been shown to induce long-term spatial and sequential learning and memory deficits in adult offspring after exposure to the drug on postnatal (P) days 11-20, but not after exposure on P1-10. Herein we further tested for the effects of MDMA (0, 5, 10 or 20 mg/kg x 2/day) after exposure on P11-20 on reference and working memory in the Morris water maze (MWM), on reference memory in the Barnes maze, and on cued learning in the visible platform version of the MWM. The MWM and Barnes mazes were counterbalanced such that half the litters received the MWM-first and the other half received the Barnes maze first. Effects on MWM performance as a function of test order were observed. For animals that received the Barnes maze first, spatial MWM learning and memory trends were seen but they were not significantly different between MDMA groups and saline controls. For those receiving the MWM-first, there are consistent impairments on all measures in the MDMA groups compared to controls on MWM performance (latency, path length, and cumulative distance from the goal). On probe trials, MDMA animals receiving the MWM-first showed increased distance from the target site compared to controls. There were no MDMA effects seen on cued trials in the MWM or on straight channel swimming trials regardless of test order, indicating that MDMA had no effects on swimming ability or on the skills needed to learn the MWM. Similarly, there were no effects of MDMA on MWM working memory regardless of test order. No MDMA effects on the Barnes maze were found regardless of test order, however, the interpretation of this finding was compromised by the poor performance of the animals on this task.

Absorption and clearance of ±3,4-methylenedioxymethamphetamine from the plasma of neonatal rats

A limited number of studies exist describing the effects of +/-3,4-methylenedioxymethamphetamine (MDMA) during perinatal development, although the number of MDMA users has increased dramatically, and this increase is greatest in people of child-bearing age. Previous experimental studies show that exposure to MDMA during part of the third trimester-equivalent (postnatal days P1-20 in rats) cause two distinct types of learning and memory deficits (sequential and spatial) if exposed on P11-20, but not if exposure occurs on P1-10. In the present study, we examined differences in the ability of neonatal rats to eliminate MDMA. Rat offspring were given a single dose of 20 mg/kg MDMA on either P1 or 11, and plasma was collected at 1 of 10 time points during a 10-h period. MDMA concentrations were assessed by liquid chromatography/mass spectrometry (LC/MS). Indices of absorption did not differ as a function of exposure age. Exposure age differences in the clearance rate and half-life of MDMA were observed, such that the P1-treated animals had a significantly more rapid clearance and a shorter half-life than P11-treated animals did. These changes are in the same direction as the behavioral differences reported previously between P1-10 and P11-20 MDMA exposure groups. However, the pharmacokinetic differences were not commensurate with the behavioral changes in that the clearance differences at the two ages are quantitative whereas the behavioral differences were qualitative (no effects from P1-10 exposure and large effects from P11-20). Although the data do not suggest a mechanism for the learning deficits, they indicate that pharmacokinetic differences may contribute to the effects seen when exposure is begun on P11.

Neurotoxic effects of MDMA (“ecstasy”) administration to neonatal rats

3,4-methylenedioxymethamphetamine damages fine serotonergic fibers and nerve terminals in adult organisms. Developing animals seem to be less susceptible to this effect, possibly due to a lack of drug-induced hyperthermia. We tested this hypothesis by producing hyperthermia in neonatal rats for 2h after each of twice-daily MDMA (10 mg/kg s.c.) or saline injections administered from postnatal days 1-4. Other drug-treated and control litters were maintained at normothermic temperatures following injection. Changes in forebrain serotonergic innervation were assessed at postnatal day 25 (serotonin transporter binding and serotonin levels), postnatal day 60 (serotonin transporter binding), and 9 months of age (serotonin transporter immunohistochemistry). We also determined the influence of MDMA treatment on apoptotic activity by means of immunohistochemistry for cleaved caspase-3 at postnatal day 5. The hippocampus showed significant MDMA-related reductions in serotonergic markers at postnatal day 25 and postnatal day 60. At 9 months, there was no effect of prior MDMA exposure on serotonin transporter-immunoreactive fiber density in the hippocampus; however, significant reductions in fiber density were observed in two neocortical areas and a hyperinnervation was found in the caudate-putamen and nucleus accumbens shell. MDMA treatment also produced a two-fold increase in the number of cleaved caspase-3-immunoreactive cells in the rostral forebrain and hippocampus. All of these effects were completely independent of pup body temperature. These findings demonstrate that neonatal MDMA administration exposure stimulates apoptotic cell death in various forebrain areas and also leads to a long-term reorganization of the forebrain serotonergic innervation. Consequently, offspring of MDMA-using women may be at heightened risk for abnormal neural and behavioral development.

Neonatal 3,4-methylenedioxymethamphetamine (ecstasy) alters dopamine and serotonin neurochemistry and increases brain-derived neurotrophic factor in the forebrain and brainstem of the rat

Growing concerns surround the risk of fetal exposure to 3,4-methylenedioxymethamphetamine (MDMA; ecstasy). Prior animal studies using neonatal rats administered MDMA from postnatal days (P) 11-20 (a period approximating third trimester brain development in humans) have demonstrated long-lasting decrements in serotonin (5-HT) and learning; however, no studies have examined the acute post-MDMA response of the brain at this early age. Specifically, it is of interest whether MDMA administration to neonatal rats produces the expected depletion of monoamines and whether the brain exhibits any ameliorative response to the pharmacologic insult. In the current study, this model was employed to determine whether forebrain and brainstem dopamine (DA) and 5-HT neurochemistry were altered 24 h after the last injection (P21), and whether brain-derived neurotrophic factor (BDNF) was upregulated in response to MDMA exposure. All forebrain structures examined (frontal cortex, hippocampus, and striatum) showed significant MDMA-induced reductions in 5-HT and its metabolite, 5-HIAA, and significant increases in the DA metabolite, HVA, as well as DA turnover (HVA/DA). In the brainstem, there were significant increases in 5-HIAA, HVA and DA turnover. BDNF was significantly increased (19-38%) in all forebrain structures and in the brainstem in MDMA-exposed neonates versus saline controls. These data suggest that MDMA exposure to the developing rat brain from P11-20 produces similar alterations in serotonin and dopamine neurochemistry to those observed from adult administrations. In addition, a compensatory increase in BDNF was observed and may be the brains ameliorative response to minimize MDMA effects. This is the first report demonstrating that MDMA exposure results in increased levels of BDNF and that such increases are correlated with changes in monoamine levels. Future research is needed to elucidate any deleterious effects MDMA-induced increases in trophic activity might have on the developing brain and to examine earlier gestational exposure periods in order to assess the risk throughout pregnancy.

Short- and long-term effects of MDMA ("ecstasy") on synaptosomal and vesicular uptake of neurotransmitters in vitro and ex vivo

3,4-Methylenedioxymethamphetamine (MDMA, "ecstasy") is a commonly abused drug which has been shown to be neurotoxic to serotonergic neurons in many species. The exact mechanism responsible for the neurotoxicity of MDMA is, however, poorly understood. In this study, the effects of MDMA on the synaptosomal and vesicular uptake of neurotransmitters were investigated. Our results show that MDMA (0.5-20 microM) reduces both synaptosomal and vesicular uptake of serotonin and dopamine in a dose dependent manner in vitro, while the uptake of glutamate and gamma-aminobutyric acid (GABA) remains unaffected. Ex vivo experiments support the importance of the monoamines, with predominant dopaminergic inhibition at short-term exposure (3 x 15 mg/kg; 2-h intervals), and exclusively serotonergic inhibition at long-term exposure (2 x 10 mg/kg per day; 4 days). This study also compares MDMA and the structurally related antidepressant paroxetine, in an attempt to reveal possible cellular mechanisms for the serotonergic toxicity of MDMA. One important difference between paroxetine and MDMA is that only MDMA has the capability of inhibiting vesicular uptake of monoamines at doses used. We suggest that inhibition of the vesicular monoamine transporter-2, and a following increase in cytoplasmatic monoamine concentrations, might be crucial for the neurotoxic effect of MDMA.

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.

Methylenedioxymethamphetamine (MDMA, Ecstasy) neurotoxicity: cellular and molecular mechanisms

Methylenedioxymethamphetamine (MDMA, Ecstasy) is a very popular drug of abuse. This has led to new intense concerns relevant to its nefarious neuropsychiatric effects. These adverse events might be related to the neurotoxic effects of the drug. Although the mechanisms of MDMA-induced neurotoxicity remain to be fully characterized, exposure to the drug can cause acute and long-term neurotoxic effects in animals and nonhuman primates. Recent studies have also documented possible toxic effects in the developing fetus. Nevertheless, there is still much debate concerning the effects of the drug in humans and how to best extrapolate animal and nonhuman primate data to the human condition. Herein, we review the evidence documenting the adverse effects of the drug in some animal models. We also discuss possible mechanisms for the development of MDMA neurotoxicity. Data supporting deleterious effects of this drug on the developing fetus are also described. Much remains to be done in order to clarify the molecular and biochemical pathways involved in the long-term neuroplastic changes associated with MDMA abuse.