Restraint as a stressor in mice: against the dopaminergic neurotoxicity of D-MDMA, low body weight mitigates restraint-induced hypothermia and consequent neuroprotection

Rodent Thermoregulation: Considerations for Tail-Cuff Blood Pressure Measurements

Noninvasive blood pressure measurement devices have gained popularity in recent years as an alternative to radiotelemetry and other invasive blood pressure measurement techniques. While many factors must be considered when choosing a measurement method, specific variables should be evaluated when using a tail-cuff blood pressure technique. Rodents have complex and dynamic thermal biology processes that involve fluctuating vasomotor tone of the tail. This and other factors that affect vascular tone, such as the autonomic response to stress, significantly affect peripheral blood flow. Awareness and consideration of thermoregulatory states and vasomotor tone can increase success and decrease variability when measuring blood pressure measurements using a tail-cuff measurement technique.

Of mice and men on MDMA: A translational comparison of the neuropsychobiological effects of 3,4-methylenedioxymethamphetamine ('Ecstasy')

MDMA (3,4-methylendioxymethamphetamine), also known as Ecstasy, is a stimulant drug recreationally used by young adults usually in dance clubs and raves. Acute MDMA administration increases serotonin, dopamine and noradrenaline by reversing the action of the monoamine transporters. In this work, we review the studies carried out over the last 30 years on the neuropsychobiological effects of MDMA in humans and mice and summarise the current knowledge. The two species differ with respect to the neurochemical consequences of chronic MDMA, since it preferentially induces serotonergic dysfunction in humans and dopaminergic neurotoxicity in mice. However, MDMA alters brain structure and function and induces hormonal, psychomotor, neurocognitive, psychosocial and psychiatric outcomes in both species, as well as physically damaging and teratogen effects. Pharmacological and genetic studies in mice have increased our knowledge of the neurochemical substrate of the multiple effects of MDMA. Future work in this area may contribute to developing pharmacological treatments for MDMA-related disorders.

Dark Classics in Chemical Neuroscience: 3,4-Methylenedioxymethamphetamine

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

The H-ARS Dose Response Relationship (DRR): Validation and Variables

Manipulations of lethally-irradiated animals, such as for administration of pharmaceuticals, blood sampling, or other laboratory procedures, have the potential to induce stress effects that may negatively affect morbidity and mortality. To investigate this in a murine model of the hematopoietic acute radiation syndrome, 20 individual survival efficacy studies were grouped based on the severity of the administration (Admn) schedules of their medical countermeasure (MCM) into Admn 1 (no injections), Admn 2 (1-3 injections), or Admn 3 (29 injections or 6-9 oral gavages). Radiation doses ranged from LD30/30 to LD95/30. Thirty-day survival of vehicle controls in each group was used to construct radiation dose lethality response relationship (DRR) probit plots, which were compared statistically to the original DRR from which all LDXX/30 for the studies were obtained. The slope of the Admn 3 probit was found to be significantly steeper (5.190) than that of the original DRR (2.842) or Admn 2 (2.009), which were not significantly different. The LD50/30 for Admn 3 (8.43 Gy) was less than that of the original DRR (8.53 Gy, p < 0.050), whereas the LD50/30 of other groups were similar. Kaplan-Meier survival curves showed significantly worse survival of Admn 3 mice compared to the three other groups (p = 0.007). Taken together, these results show that stressful administration schedules of MCM can negatively impact survival and that dosing regimens should be considered when constructing DRR to use in survival studies.

Drug-induced neurotoxicity in addiction medicine: From prevention to harm reduction

Neurotoxicity is considered as a major cause of neurodegenerative disorders. Most drugs of abuse have nonnegligible neurotoxic effects many of which are primarily mediated by several dopaminergic and glutamatergic neurotransmitter systems. Although many researchers have investigated the medical and cognitive consequences of drug abuse, the neurotoxicity induced by these drugs still requires comprehensive attention. The science of neurotoxicity promises to improve preventive and therapeutic strategies for brain disorders such as Alzheimer disease and Parkinson's disease. However, its clinical applications for addiction medicine remain to be defined adequately. This chapter reviews the most commonly discussed mechanisms underlying neurotoxicity induced by common drugs of abuse including amphetamines, cocaine, opiates, and alcohol. In addition, the known factors that trigger and/or predispose to drug-induced neurotoxicity are discussed. These factors include drug-related, individual-related, and environmental insults. Moreover, we introduce some of the potential pharmacological antineurotoxic interventions deduced from experimental animal studies. These interventions involve various targets such as dopaminergic system, mitochondria, cell death signaling, and NMDA receptors, among others. We conclude the chapter with a discussion of addicted patients who might benefit from such interventions.

Ecstasy (MDMA) Alters Cardiac Gene Expression and DNA Methylation: Implications for Circadian Rhythm Dysfunction in the Heart

MDMA (ecstasy) is an illicit drug that stimulates monoamine neurotransmitter release and inhibits reuptake. MDMA's acute cardiotoxicity includes tachycardia and arrhythmia which are associated with cardiomyopathy. MDMA acute cardiotoxicity has been explored, but neither long-term MDMA cardiac pathological changes nor epigenetic changes have been evaluated. Microarray analyses were employed to identify cardiac gene expression changes and epigenetic DNA methylation changes. To identify permanent MDMA-induced pathogenetic changes, mice received daily 10- or 35-day MDMA, or daily 10-day MDMA followed by 25-day saline washout (10 + 25 days). MDMA treatment caused differential gene expression (p < .05, fold change >1.5) in 752 genes following 10 days, 558 genes following 35 days, and 113 genes following 10-day MDMA + 25-day saline washout. Changes in MAPK and circadian rhythm gene expression were identified as early as 10 days. After 35 days, circadian rhythm genes (Per3, CLOCK, ARNTL, and NPAS2) persisted to be differentially expressed. MDMA caused DNA hypermethylation and hypomethylation that was independent of gene expression; hypermethylation of genes was found to be 71% at 10 days, 68% at 35 days, and 91% at 10 + 25 days washout. Differential gene expression paralleled DNA methylation in 22% of genes at 10-day treatment, 17% at 35 days, and 48% at 10 + 25 days washout. We show here that MDMA induced cardiac epigenetic changes in DNA methylation where hypermethylation predominated. Moreover, MDMA induced gene expression of key elements of circadian rhythm regulatory genes. This suggests a fundamental organism-level event to explain some of the etiologies of MDMA dysfunction in the heart.

Analgesics, sedatives, anticonvulsant drugs, and the cooled brain

Multiple randomized controlled trials have shown that prolonged, moderate cerebral hypothermia initiated within a few hours after severe hypoxia-ischemia and continued until resolution of the acute phase of delayed cell death reduces mortality and improves neurodevelopmental outcome in term infants. The challenge is now to find ways to further improve outcomes. In the present review, we critically examine the evidence that conventional analgesic, sedative, or anticonvulsant agents might improve outcomes, in relation to the known window of opportunity for effective protection with hypothermia. This review strongly indicates that there is insufficient evidence to recommend routine use of these agents during therapeutic hypothermia. Further systematic research into the effects of pain and stress on the injured brain, and their treatment during hypothermia, is essential to guide the rational development of clinical treatment protocols.

An investigation of the challenges in reconstructing PET images of a freely moving animal

Imaging the brain of a freely moving small animal using positron emission tomography (PET) while simultaneously observing its behaviour is an important goal for neuroscience. While we have successfully demonstrated the use of line-of-response (LOR) rebinning to correct the head motion of confined animals, a large proportion of events may need to be discarded because they either 'miss' the detector array after transformation or fall out of the acceptance range of a sinogram. The proportion of events that would have been measured had motion not occurred, so-called 'lost events', is expected to be even larger for freely moving animals. Moreover, the data acquisition in the case of a freely moving animal is further complicated by a complex attenuation field. The aims of this study were (a) to characterise the severity of the 'lostevents' problem for the freely moving animal scenario, and(b) to investigate the relative impact of attenuation correction errors on quantitative accuracy of reconstructed images. A phantom study was performed to simulate the uncorrelated motion of a target and non-target sourcevolume. A small animal PET scanner was used to acquirelist-mode data for different sets of phantom positions. The list-mode data were processed using the standard LOR rebinning approach, and multiple frame variants of this designed to reduce discarded events. We found that LOR rebinning caused up to 86 % 'lost events', and artifacts that we attribute to incomplete projections, when applied to a freely moving target. This fraction was reduced by up to 18 % using the variant approaches, resulting in slightly reduced image artifacts. The effect of the non-target compartment on attenuation correction of the target volume was surprisingly small. However, for certain poses where the target and non-target volumes are aligned transaxially in the field-of-view, the attenuation problem becomes more complex and sophisticated correction methods will be required. We conclude that there are limitations with the LOR rebinning approach and simplified attenuation correction for freely moving animals requiring the development and validation of more sophisticated approaches.

A robust and reliable non-invasive test for stress responsivity in mice

Stress and an altered stress response have been associated with many multifactorial diseases, such as psychiatric disorders or neurodegenerative diseases. As currently mouse mutants for each single gene are generated and phenotyped in a large-scale manner, it seems advisable also to test these mutants for alterations in their stress responses. Here we present the determinants of a robust and reliable non-invasive test for stress-responsivity in mice. Stress is applied through restraining the mice in tubes and recording behavior in the Open Field 20 min after cessation of the stress. Two hours, but not 15 or 50 min of restraint lead to a robust and reproducible increase in distance traveled and number of rearings during the first 5 min in the Open Field in C57BL/6 mice. This behavioral response is blocked by the corticosterone synthesis inhibitor metyrapone, but not by RU486 treatment, indicating that it depends on corticosteroid secretion, but is not mediated via the glucocorticoid receptor type II. We assumed that with a stress duration of 15 min one could detect hyper-responsivity, and with a stress duration of 2 h hypo-responsivity in mutant mouse lines. This was validated with two mutant lines known to show opposing effects on corticosterone secretion after stress exposure, corticotropin-releasing hormone (CRH) over-expressing mice and CRH receptor 1 knockout (KO) mice. Both lines showed the expected phenotype, i.e., increased stress responsivity in the CRH over-expressing mouse line (after 15 min restraint stress) and decreased stress responsivity in the CRHR1-KO mouse line (after 2 h of restraint stress). It is possible to repeat the acute stress test several times without the stressed animal adapting to it, and the behavioral response can be robustly evoked at different ages, in both sexes and in different mouse strains. Thus, locomotor and rearing behavior in the Open Field after an acute stress challenge can be used as reliable, non-invasive indicators of stress responsivity and corticosterone secretion in mice.

Effect of physical restraint on the limits of thermoregulation in telemetered rats

Physical restraint of rodents is needed for nose-only exposure to airborne toxicants and is also used as a means of psychological stress. Hyperthermia is often observed in restrained rats, presumably as a result of impairments in heat dissipation. However, such a hyperthermic response should be dependent on the prevailing ambient conditions. To understand how ambient temperature (T(a)) affects the thermoregulatory response to restraint, core temperature (T(c)) and heart rate (HR) were monitored by telemetry in rats subjected to 1 h of physical restraint while T(a) was maintained at 14-30 °C in 2 °C increments. The T(c) of unrestrained rats was unaffected by T(a). During restraint, T(c) was elevated at ambient temperatures with the exception of 14 °C, at which the rats became mildly hypothermic. There was an inverse relationship between T(a) and HR in both unrestrained and restrained rats; however, HR was significantly elevated in restrained rats at all ambient temperatures except 22 and 24 °C. Heat loss from the tail, estimated from T(c) and tail skin temperature, was markedly reduced at all but the highest ambient temperatures in restrained rats. The data suggest that the T(a) limits of normothermia are narrowed in the restrained rat. That is, between 16 and 20 °C, the rat maintains a relatively stable T(c) that is slightly elevated above that of the unrestrained rat. At ambient temperatures above or below this range, the rat shows signs of hyperthermia and hypothermia, respectively. In contrast, the limits of normothermia for unrestrained rats range from 14 (or lower) to 30 °C. Overall, the ideal T(a) for restrained rats appears to be 20 °C and no higher than 22 °C for the thermoregulatory system to maintain a regulated T(c) in rats well adapted to physical restraint.

The role of monoamines in the changes in body temperature induced by 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) and its derivatives

Hyperthermia is probably the most widely known acute adverse event that can follow ingestion of 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) by recreational users. The effect of MDMA on body temperature is complex because the drug has actions on all three major monoamine neurotransmitters [5-hydroxytryptamine (5-HT), dopamine and noradrenaline], both by amine release and by direct receptor activation. Hyperthermia and hypothermia can be induced in laboratory animals by MDMA, depending on the ambient temperature, and involve both central thermoregulation and peripheral changes in blood flow and thermogenesis. Acute 5-HT release is not directly responsible for hyperthermia, but 5-HT receptors are involved in modulating the hyperthermic response. Impairing 5-HT function with a neurotoxic dose of MDMA or p-chlorophenylalanine alters the subsequent MDMA-induced hyperthermic response. MDMA also releases dopamine, and evidence suggests that this transmitter is involved in both the hyperthermic and hypothermic effects of MDMA in rats. The noradrenergic system is also involved in the hyperthermic response to MDMA. MDMA activates central alpha(2A)-adrenoceptors and peripheral alpha(1)-adrenoceptors to produce cutaneous vasoconstriction to restrict heat loss, and beta(3)-adrenoceptors in brown adipose tissue to increase heat generation. The hyperthermia occurring in recreational users of MDMA can be fatal, but data reviewed here indicate that it is unlikely that any single pharmaceutical agent will be effective in reversing the hyperthermia, so careful body cooling remains the principal clinical approach. Crucially, educating recreational users about the potential dangers of hyperthermia and the control of ambient temperature should remain key approaches to prevent this potentially fatal problem.

Sex differences in stress-induced hyperthermia in rats: restraint versus confinement

Studies using restraint to induce psychological stress consistently report the expected hyperthermic response in core body temperature (CBT), but many also report a hypothermic response that precedes the hyperthermia. To understand the conditions that produce hypothermia, and to study sex differences in stress-induced hyperthermia, we measured CBT in male and female rats at 70 and 180 days of age in response to two types of stressors: immobilization through restraint (Plexiglas restrainer) and confinement in a small area (circular wire mesh cylinders that allowed free airflow). Restraint early in the light period induced hypothermia only in 180-day-old males, with no hyperthermia observed during the 30-minute restraint period. Increases in humidity and temperature of the microenvironment due to the larger body weight at this age may contribute to the hypothermia. Hyperthermia during restraint in 70-day-old males was significantly attenuated and delayed in onset compared to the rise in females. All females exhibited a CBT rise of approximately 1.3 degrees C occurring 10-15 min after the onset of restraint. Restraint early in the dark period induced no significant change in CBT in males of either age during immobilization, while females exhibited a small rise of approximately 0.5 degrees C. Confinement early in the light period induced a significant rise of approximately 1.5 degrees C in all groups, with no preceding hypothermia. However, the male response was significantly delayed compared to females. Overall, these results indicate that CBT changes during restraint likely involve both anxiogenic and physiological components, while the marked hyperthermia during confinement is primarily psychological in both sexes.

The use of radiotelemetry to assess the time needed to acclimatize guineapigs following several hours of ground transport

The objective of this study was to investigate the effect of ground transportation on guineapigs. Physiological parameters, i.e. heart rate (HR), body temperature (BT) and activity (ACT), were measured before and after transport, using previously implanted radiotelemetry transmitters. Body weight was measured before and after transport. After a postsurgical recovery period and data recording at the breeder's facility, the animals were transported for 2.25 h (Group 1) and for 7.5 h (Group 2) to a different animal facility. Data collection started immediately after arrival at the second animal facility. All parameters measured changed significantly after transport. These results suggest that a 10- to 12-day period is required for guineapigs to return to pre-transport levels of HR, BT and ACT.

Stress and hypothermia in mice in a nose-only cigarette smoke exposure system

In nose-only exposure systems, animals need to be restrained inside a tube, which leads to stress. Stress is known to cause hyperthermia in rodents. Chronically repeated episodes of hyperthermia could be detrimental to animal health and influence results of nose-only exposure studies. Therefore we investigated whether hyperthermia occurred in male C57BL/6J mice that were restrained for increasing lengths of time, using nosepieces held at room temperature, preheated at 37 degrees C, or thermostat controlled at different temperatures, with and without exposure to different concentrations of cigarette smoke. Body temperature, body weight, plasma corticosterone levels, and adrenal weights were recorded. Restraint using nosepieces at room temperature caused a time-dependent decrease in body temperature, which could be reversed by preheating the nosepieces to 37 degrees C. Cigarette smoke dose-dependently caused an additional decrease, which was counteracted by controlling nosepiece temperature at 38 degrees C. During 3 mo of exposure using heated nosepieces, Delta body temperature remained constant. Body weight gain did not differ between smoke-exposed and room air-breathing animals exposed using either heated or room-temperature nosepieces, but both groups gained significantly less weight, while adrenal weights were significantly and similarly increased, when compared to unrestrained littermates. Plasma corticosterone levels did not differ between the three groups. In conclusion, during restraint in nose-only exposure tubes with room temperature metal nosepieces, mice suffer a pronounced hypothermia. Preventing this by heating the nosepieces does not reduce the stress experienced by the animals.

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

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

Sensitive indicators of injury reveal hippocampal damage in C57BL/6J mice treated with kainic acid in the absence of tonic-clonic seizures

Sensitive indices of neural injury were used to evaluate the time course of kainic acid (KA)-induced hippocampal damage in adult C57BL/6J mice (4 months), a strain previously reported to be resistant to kainate-induced neurotoxicity. Mice were injected systemically with saline or kainate, scored for seizure severity (Racine scale), and allowed to survive 12 h, one, three, or seven days following which they were evaluated for neuropathological changes using histological or biochemical endpoints. Most kainate-treated mice exhibited limited seizure activity (stage 1); however, cupric-silver and Fluoro-Jade B stains revealed significant damage by 12 h post-treatment. Immunohistochemistry and immunoassay of glial fibrillary acidic protein and lectin staining revealed a strong treatment-induced reactive gliosis and microglial activation. Immunostaining for immunoglobulin G revealed a kainate-induced breach in the blood-brain barrier. Nissl and hematoxylin stains provided little information regarding neuronal damage, but revealed the identity of non-resident cells which infiltrated the pyramidal layer. Our data suggest sensitive indicators of neural injury evaluated over a time course, both proximal and distal to treatment, are necessary to reveal the full extent of neuropathological changes which may be underestimated by traditional histological stains. The battery of neuropathological indices reported here reveals the C57BL/6J mouse is sensitive to excitotoxic neural damage caused by kainic acid, in the absence of tonic-clonic seizures.

A review of the mechanisms involved in the acute MDMA (ecstasy)-induced hyperthermic response

The predominant severe acute adverse effect following ingestion of 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) by recreational users is hyperthermia which can induce other associated clinical problems and occasionally death. There is no pharmacologically specific treatment. MDMA also induces dose-dependent hyperthermia in experimental animals. This review examines the consequences of MDMA administration on body temperature in humans and rodents. In rats hyperthermia results primarily from dopamine release and is influenced by dose, ambient temperature and other housing conditions. The response is increased in rats with a prior MDMA-induced neurotoxic lesion of 5-hydroxytryptamine (5-HT) nerve endings. Increased MDMA-induced locomotor activity appears to play no role in the hyperthermic response. However, the size of the acute hyperthermic response plays a major role in determining the severity of the subsequent neurotoxicity. These results suggest that any MDMA-induced hyperthermic response will be enhanced in hot, crowded dance club conditions and that ingesting the drug in such conditions increases the possibility of subsequent cerebral neurotoxic effect.

Brain concentrations of d-MDMA are increased after stress

RATIONALE

In the mouse but not the rat, d-3,4-methylenedioxymethamphetamine (d-MDMA) is a dopaminergic neurotoxicant. Various stressors and hypothermia protect against d-MDMA-induced neurotoxicity through unknown mechanisms, one of which could be a reduction in the distribution of d-MDMA to the brain.

OBJECTIVES

We determined striatal levels of d-MDMA in relation to body temperature in mice exposed to a neurotoxic regimen of d-MDMA in the presence or absence of various stressors.

METHODS

Female C57BL6/J mice received a neurotoxic regimen of d-MDMA (15.0 mg/kg s.c. as the base every 2 hx4) alone or in combination with manipulations with a known neuroprotective status. d-MDMA levels were determined by HPLC with fluorometric detection while rectal temperature provided core temperature status. Levels of dopamine, tyrosine hydroxylase and GFAP were used to assess neurotoxicity.

RESULTS

Restraint, ethanol co-treatment and cold stress were neuroprotective, caused hypothermia and increased striatal d-MDMA levels by 4- to 7-fold. Corticosterone treatment, as a stress mimic, did not alter striatal d-MDMA or temperature and was not protective. The protective glutamate receptor antagonist, MK-801, doubled striatal d-MDMA levels and caused hypothermia.

CONCLUSIONS

Although stress and other protective manipulations can alter the striatal concentration of d-MDMA their hypothermia-inducing properties appear a more likely determinant of their neuroprotection against the striatal dopaminergic neurotoxicity of d-MDMA.

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

RATIONALE AND OBJECTIVES

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

RESULTS AND DISCUSSION

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

The 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.

Chronic treatment with supraphysiological levels of corticosterone enhances D-MDMA-induced dopaminergic neurotoxicity in the C57BL/6J female mouse

Chronic stress and extended periods of elevated circulating glucocorticoids have been reported to exacerbate excitotoxicity-induced hippocampal neuronal injury in rat. Despite continued interest in the effects of protracted exposure to stress or glucocorticoids, there has been little examination of how other types of neurotoxicity may be exacerbated or blocked, by stress. Here we examined the effects of chronic supraphysiologic levels of corticosterone on D-3,4-methylenedioxymethamphetamine (D-MDMA)-induced striatal dopaminergic neurotoxicity in the female C57BL/6J mouse. Corticosterone (5 mg, 15 mg or placebo) pellets were implanted to continuously elevate circulating glucocorticoids and create a model of the ultimate effect of chronic activation of the hypothalamic-pituitary-adrenal axis. After 7 days, a neurotoxic regimen of D-MDMA was administered (20 mg/kg s.c. every 2 hx4); thymus, spleen, striatum and hippocampus were collected 72 h later. Significant involution of thymus and spleen confirmed the bioavailability of the corticosterone at both dosages. D-MDMA increased the striatal levels of the astrocyte-localized protein glial fibrillary acidic protein (GFAP, a marker of gliosis); both dosages of corticosterone exacerbated this increase but only the 15 mg pellet exacerbated the decrease in tyrosine hydroxylase protein. Corticosterone alone or in combination with D-MDMA produced no neural injury in hippocampus, as measured by GFAP. Our work indicates corticosterone was able to increase the vulnerability of the striatum, but not the hippocampus to D-MDMA. An examination of other mouse strains and models of neurotoxic injury would be useful in determining the general validity of the glucocorticoid neuroendangerment hypothesis.

d-MDMA during vitamin E deficiency: effects on dopaminergic neurotoxicity and hepatotoxicity

The mechanism of 3,4-methylenedioxymethamphetamine (d-MDMA)-induced neurotoxicity may involve formation of toxic radical species. Endogenous defenses against toxic radical species include tissue stores of vitamin E, and thiols. We examined whether vitamin E deficiency could alter d-MDMA-induced neurotoxicity by administration of the drug to animals with diet induced vitamin E deficiency. Brain vitamin E levels in deficient mice were reduced 75% compared to sufficient animals. Animals received d-MDMA 5 or 10 mg/kg or saline (delivered every 2 hx4, s.c.). Diet slightly altered d-MDMA-induced temperature modulation. In brain, MDMA treatment reduced vitamin E, total antioxidant reserve and protein thiols 72 h after the first dose. In liver, MDMA treatment reduced glutathione and total antioxidant reserve at the same time point. The vitamin E-deficient group, treated with the low dose of d-MDMA, exhibited neurotoxic responses, including reduced striatal dopamine (47%) and elevated GFAP protein (3-fold): while the sufficient diet group was not altered. The higher d-MDMA dose caused neurotoxic responses in both diet groups. Liver toxicity was determined by histopathologic examination. d-MDMA caused hepatic necrosis that was more severe in vitamin E deficient than sufficient mice. These data indicate that (1) d-MDMA administration reduces antioxidant measures at a time coincident with d-MDMA-induced neuronal damage and (2) vitamin E deficiency increases susceptibility to d-MDMA-induced neurotoxicity and hepatic necrosis.