Brain concentrations of d-MDMA are increased after stress

Notch1 haploinsufficiency in mice accelerates adipogenesis

Notch signaling has been recognized recently as a key regulator of metabolism. Here, we determined the role of Notch1 in adipogenesis in wild-type (WT) and Notch1 hetero-mutant (N1+/-) mice provided with 12-week normal or high-fat diet. Haploinsufficiency of Notch1 was associated with adipose tissue accumulation despite similar food intake. White adipose tissue (WAT) of N1+/- showed accumulation of adipogenic cells (CD34+CD68+ cells), crown-like structures, and upregulation of cell proliferation markers (cyclin D1 and Ki67). Notch1 expression in WAT reached peak levels in 8-week-old WT mice in parallel with fat accumulation, especially under HF/HS-feeding, whereas such increment was blunted in N1+/- mice. Downstream of Notch1 haploinsufficiency, over-expression of adipogenic factors PPARγ and C/EBPα was noted following down-regulation of downstream transcriptional factors of Notch signaling (Hes-1, Pref-1, and Sox9). Both pharmacological Notch signal inhibition and Notch1 knockdown enhanced adipogenesis of 3T3-L1 preadipocytes. N1+/- mice showed impaired glucose and insulin tolerance with downregulation of IRS-1 and GLUT4 in WAT after high-fat diet. Taken together, our results suggest that haploinsufficiency of Notch1 promotes fat accumulation and adipogenesis and provides a mechanistic link between Notch signaling and development of metabolic syndrome.

Combining ecstasy and ethanol: higher risk for toxicity? A review

Ecstasy use is commonly combined with ethanol consumption. While combination drug use in general is correlated with a higher risk for toxicity, the risk of the specific combination of ecstasy (3,4-methylenedioxymethamphetamine (MDMA)) and ethanol is largely unknown. Therefore, we have reviewed the literature on changes in MDMA pharmacokinetics and pharmacodynamics due to concurrent ethanol exposure in human, animal and in vitro studies. MDMA pharmacokinetics appear unaffected: the MDMA blood concentration after concurrent exposure to MDMA and ethanol was comparable to lone MDMA exposure in multiple human placebo-controlled studies. In contrast, MDMA pharmacodynamics were affected: locomotor activity increased and body temperature decreased after concurrent exposure to MDMA and ethanol compared to lone MDMA exposure. Importantly, these additional ethanol effects were consistently observed in multiple animal studies. Additional ethanol effects have also been reported on other pharmacodynamic aspects, but are inconclusive due to a low number of studies or due to inconsistent findings. These investigated pharmacodynamic aspects include monoamine brain concentrations, neurological (psychomotor function, memory, anxiety, reinforcing properties), cardiovascular, liver and endocrine effects. Although only a single or a few studies were available investigating these aspects, most studies indicated an aggravation of MDMA-induced effects upon concurrent ethanol exposure. In summary, concurrent ethanol exposure appears to increase the risk for MDMA toxicity. Increased toxicity is due to an aggravation of MDMA pharmacodynamics, while MDMA pharmacokinetics is largely unaffected. Although a significant attenuation of the MDMA-induced increase of body temperature was observed in animal studies, its relevance for human exposure remains unclear.

The combined effects of 3,4-methylenedioxymethamphetamine (MDMA) and selected substituted methcathinones on measures of neurotoxicity

The rise in popularity of substituted methcathinones (aka "bath salts") has increased the focus on their neurotoxic effects. Two commonly abused methcathinones, 3,4-methylenedioxymethcathinone (methylone, MDMC) and 3,4-methylenedioxypyrovalerone (MDPV), are often concomitantly ingested with the illicit drug 3,4-methylenedioxymethamphetamine (MDMA). To examine potential neurotoxic effects of these drug combinations, C57BL/6J mice were administered 4 i.p. injection of the drugs, at 2h intervals, either singularly: MDMA 15 or 30mg/kg, methylone 20mg/kg, MDPV 1mg/kg; or in combination: methylone/MDMA 20/15mg/kg, MDPV/MDMA 1/15mg/kg. Drug effects on thermoregulation were characterized and striatal tissue analyzed after 2 or 7days for dopamine (DA) and tyrosine hydroxylase (TH) levels, as well as glial fibrillary acidic protein (GFAP) expression. Two days following drug administration, DA and TH were decreased only in the MDMA 30mg/kg group, whereas GFAP expression was dose-dependently increased by MDMA alone. While the combination of the methcathinones with the lower MDMA dose did not affect DA or TH levels, both blocked the MDMA-induced increase in GFAP expression. Seven days following drug administration, there were no significant differences in DA, TH, or GFAP for any treatment group, indicating that changes in DA, TH, and GFAP were transient. Five of the six drug groups exhibited acute hypothermia followed by gradually increasing temperatures. Animals treated with MDPV did not exhibit these biphasic temperature changes, and resembled the saline group. These results indicate that specific effects of both methylone and MDPV on DA depletion or astrocyte activation in the striatum are not additive with effects of MDMA, but block astrogliosis caused by MDMA alone. Additionally, MDPV modulates thermoregulation through a different mechanism than methylone or MDMA.

Effect of crowding, temperature and age on glia activation and dopaminergic neurotoxicity induced by MDMA in the mouse brain

3,4-methylenedyoxymethamphetamine (MDMA or "ecstasy"), a recreational drug of abuse, can induce glia activation and dopaminergic neurotoxicity. Since MDMA is often consumed in crowded environments featuring high temperatures, we studied how these factors influenced glia activation and dopaminergic neurotoxicity induced by MDMA. C57BL/6J adolescent (4 weeks old) and adult (12 weeks old) mice received MDMA (4×20mg/kg) in different conditions: 1) while kept 1, 5, or 10×cage at room temperature (21°C); 2) while kept 5×cage at either room (21°C) or high (27°C) temperature. After the last MDMA administration, immunohistochemistry was performed in the caudate-putamen for CD11b and GFAP, to mark microglia and astroglia, and in the substantia nigra pars compacta for tyrosine hydroxylase, to mark dopaminergic neurons. MDMA induced glia activation and dopaminergic neurotoxicity, compared with vehicle administration. Crowding (5 or 10 mice×cage) amplified MDMA-induced glia activation (in adult and adolescent mice) and dopaminergic neurotoxicity (in adolescent mice). Conversely, exposure to a high environmental temperature (27°C) potentiated MDMA-induced glia activation in adult and adolescent mice kept 5×cage, but not dopaminergic neurotoxicity. Crowding and exposure to a high environmental temperature amplified MDMA-induced hyperthermia, and a positive correlation between body temperature and activation of either microglia or astroglia was found in adult and adolescent mice. These results provide further evidence that the administration setting influences the noxious effects of MDMA in the mouse brain. However, while crowding amplifies both glia activation and dopaminergic neurotoxicity, a high environmental temperature exacerbates glia activation only.

Psychostimulants and brain dysfunction: a review of the relevant neurotoxic effects

Psychostimulants abuse is a major public concern because is associated with serious health complications, including devastating consequences on the central nervous system (CNS). The neurotoxic effects of these drugs have been extensively studied. Nevertheless, numerous questions and uncertainties remain in our understanding of these toxic events. Thus, the purpose of the present manuscript is to review cellular and molecular mechanisms that might be responsible for brain dysfunction induced by psychostimulants. Topics reviewed include some classical aspects of neurotoxicity, such as monoaminergic system and mitochondrial dysfunction, oxidative stress, excitotoxicity and hyperthermia. Moreover, recent literature has suggested new phenomena regarding the toxic effects of psychostimulants. Thus, we also reviewed the impact of these drugs on neuroinflammatory response, blood-brain barrier (BBB) function and neurogenesis. Assessing the relative importance of these mechanisms on psychostimulants-induced brain dysfunction presents an exciting challenge for future research efforts. This article is part of the Special Issue entitled 'CNS Stimulants'.

3,4-Methylenedioxy-methamphetamine induces in vivo regional up-regulation of central nicotinic receptors in rats and potentiates the regulatory effects of nicotine on these receptors

Nicotine (NIC), the main psychostimulant compound of smoked tobacco, exerts its effects through activation of central nicotinic acetylcholine receptors (nAChR), which become up-regulated after chronic administration. Recent work has demonstrated that the recreational drug 3,4-methylenedioxy-methamphetamine (MDMA) has affinity for nAChR and also induces up-regulation of nAChR in PC 12 cells. Tobacco and MDMA are often consumed together. In the present work we studied the in vivo effect of a classic chronic dosing schedule of MDMA in rats, alone or combined with a chronic schedule of NIC, on the density of nAChR and on serotonin reuptake transporters. MDMA induced significant decreases in [(3)H]paroxetine binding in the cortex and hippocampus measured 24h after the last dose and these decreases were not modified by the association with NIC. In the prefrontal cortex, NIC and MDMA each induced significant increases in [(3)H]epibatidine binding (29.5 and 34.6%, respectively) with respect to saline-treated rats, and these increases were significantly potentiated (up to 72.1%) when the two drugs were associated. Also in this area, [(3)H]methyllycaconitine binding was increased a 42.1% with NIC+MDMA but not when they were given alone. In the hippocampus, MDMA potentiated the α7 regulatory effects of NIC (raising a 25.5% increase to 52.5%) but alone was devoid of effect. MDMA had no effect on heteromeric nAChR in striatum and a coronal section of the midbrain containing superior colliculi, geniculate nuclei, substantia nigra and ventral tegmental area. Specific immunoprecipitation of solubilised receptors suggests that the up-regulated heteromeric nAChRs contain α4 and β2 subunits. Western blots with specific α4 and α7 antibodies showed no significant differences between the groups, indicating that, as reported for nicotine, up-regulation caused by MDMA is due to post-translational events rather than increased receptor synthesis.

The neurotoxicity of hallucinogenic amphetamines in primary cultures of hippocampal neurons

3,4-Methylenedioxymethamphetamine (MDMA or "Ecstasy") and 2,5-dimethoxy-4-iodoamphetamine hydrochloride (DOI) are hallucinogenic amphetamines with addictive properties. The hippocampus is involved in learning and memory and seems particularly vulnerable to amphetamine's neurotoxicity. We evaluated the neurotoxicity of DOI and MDMA in primary neuronal cultures of hippocampus obtained from Wistar rat embryos (E-17 to E-19). Mature neurons after 10 days in culture were exposed for 24 or 48 h either to MDMA (100-800 μM) or DOI (10-100 μM). Both the lactate dehydrogenase (LDH) release and the tetrazolium-based (MTT) assays revealed a concentration- and time-dependent neuronal death and mitochondrial dysfunction after exposure to both drugs. Both drugs promoted a significant increase in caspase-8 and caspase-3 activities. At concentrations that produced similar levels of neuronal death, DOI promoted a higher increase in the activity of both caspases than MDMA. In the mitochondrial fraction of neurons exposed 24h to DOI or MDMA, we found a significant increase in the 67 kDa band of apoptosis inducing factor (AIF) by Western blot. Moreover, 24h exposure to DOI promoted an increase in cytochrome c in the cytoplasmatic fraction of neurons. Pre-treatment with an antibody raised against the 5-HT(2A)-receptor (an irreversible antagonist) greatly attenuated neuronal death promoted by 48 h exposure to DOI or MDMA. In conclusion, hallucinogenic amphetamines promoted programmed neuronal death involving both the mitochondria machinery and the extrinsic cell death key regulators. Death was dependent, at least in part, on the stimulation of the 5-HT(2A)-receptors.

Chronic exposure to corticosterone enhances the neuroinflammatory and neurotoxic responses to methamphetamine

Up-regulation of proinflammatory cytokines and chemokines in brain ("neuroinflammation") accompanies neurological disease and neurotoxicity. Previously, we documented a striatal neuroinflammatory response to acute administration of a neurotoxic dose of methamphetamine (METH), i.e. one associated with evidence of dopaminergic terminal damage and activation of microglia and astroglia. When we used minocycline to suppress METH-induced neuroinflammation, indices of dopaminergic neurotoxicity were not affected, but suppression of neuroinflammation was incomplete. Here, we administered the classic anti-inflammatory glucocorticoid, corticosterone (CORT), in an attempt to completely suppress METH-related neuroinflammation. METH alone caused large increases in striatal proinflammatory cytokine/chemokine mRNA and subsequent astrocytic hypertrophy, microglial activation, and dopaminergic nerve terminal damage. Pre-treatment of mice with acute CORT failed to prevent neuroinflammatory responses to METH. Surprisingly, when mice were pre-treated with chronic CORT in the drinking water, an enhanced striatal neuroinflammatory response to METH was observed, an effect that was accompanied by enhanced METH-induced astrogliosis and dopaminergic neurotoxicity. Chronic CORT pre-treatment also sensitized frontal cortex and hippocampus to mount a neuroinflammatory response to METH. Because the levels of chronic CORT used are associated with high physiological stress, our data suggest that chronic CORT therapy or sustained physiological stress may sensitize the neuroinflammatory and neurotoxicity responses to METH.

Effect of intermittent exposure to ethanol and MDMA during adolescence on learning and memory in adult mice

Background

Heavy binge drinking is increasingly frequent among adolescents, and consumption of 3,4-methylenedioxymethamphetamine (MDMA) is often combined with ethanol (EtOH). The long-lasting effects of intermittent exposure to EtOH and MDMA during adolescence on learning and memory were evaluated in adult mice using the Hebb-Williams maze.

Methods

Adolescent OF1 mice were exposed to EtOH (1.25 g/kg) on two consecutive days at 48-h intervals over a 14-day period (from PD 29 to 42). MDMA (10 or 20 mg/kg) was injected twice daily at 4-h intervals over two consecutive days, and this schedule was repeated six days later (PD 33, 34, 41 and 42), resulting in a total of eight injections. Animals were initiated in the Hebb-Williams maze on PND 64. The concentration of brain monoamines in the striatum and hippocampus was then measured.

Results

At the doses employed, both EtOH and MDMA, administered alone or together, impaired learning in the Hebb-Williams maze, as treated animals required more time to reach the goal than their saline-treated counterparts. The groups treated during adolescence with EtOH, alone or plus MDMA, also presented longer latency scores and needed more trials to reach the acquisition criterion score. MDMA induced a decrease in striatal DA concentration, an effect that was augmented by the co-administration of EtOH. All the treatment groups displayed an imbalance in the interaction DA/serotonin.

Conclusions

The present findings indicate that the developing brain is highly vulnerable to the damaging effects of EtOH and/or MDMA, since mice receiving these drugs in a binge pattern during adolescence exhibit impaired learning and memory in adulthood.

Distribution of methamphetamine and its metabolite amphetamine in acute and subacute ethanol-methamphetamine combination abuse model rats

The aim of this study is to investigate the distribution of methamphetamine (MA) and its metabolite amphetamine (AP) in rat models of acute and subacute MA-ethanol combination abuse. Rats were fed with 20% ethanol for 4 weeks (chronic active-drinking group), and MA was injected intraperitoneally into chronically drinking and normal rats over 5 and 14 days, respectively. Then the rats from the acute and subacute combination abuse groups were euthanized, and ethanol, MA, and AP concentrations in samples were quantified. Except for the similar ethanol concentrations among acute and subacute groups, the MA and AP levels between groups were quite different. The concentrations of MA and AP in rats' liver, lung, kidney, and brain were much higher than other tissues, regardless of combination with ethanol. Also, MA and AP levels in subacute rats groups were higher than those in acute groups, and the levels of MA and the formation of AP in rats subjected to the combination abuse with ethanol were higher than in MA-only intoxicated rats. We conclude that ethanol has no bearing on the MA and AP distribution in body fluids and tissues, yet it can increase MA levels and markedly accelerate the formation of AP in combination-abuse rats. Comparing the acute and subacute combination-abuse rats' samples, it can be deduced that various accumulated amounts of MA and AP were unaffected by ethanol, even after multi-dose injection, regardless of acute or subacute use.

Behavioural and neuroinflammatory effects of the combination of binge ethanol and MDMA in mice

RATIONALE

Binge drinking is a common pattern of alcohol consumption among young people. Binge drinkers are especially susceptible to brain damage when other substances are co-administered, in particular, 3,4-methylendioxymethamphetamine (MDMA).

OBJECTIVE

To evaluate the behavioural consequences of voluntary binge ethanol consumption, alone and in combination to MDMA. Also, to elucidate the effects of the combined consumption of these two drugs on neuroinflammation.

MATERIALS AND METHODS

Adolescent mice received MDMA (MDMA-treated mice), ethanol (ethanol-treated mice group) or both (ethanol plus MDMA-treated mice). Drinking in the dark (DID) procedure was used as a model of binge. Body temperature, locomotor activity, motor coordination, anxiety-like and despair behaviour in adolescent mice were evaluated 48 h, 72 h, and 7 days after the treatments. Also, neuroinflammatory response to these treatments was measured in the striatum.

RESULTS

The hyperthermia observed in MDMA-treated mice was abolished by pre-exposition to ethanol. Ethanol plus MDMA-treated mice showed lower locomotor activity. Ethanol-treated mice showed motor coordination impairment and increased despair behaviour. Anxiety-like behaviour was only seen in animals that were treated with both drugs. Contrarily, neuroinflammation was mostly seen in animals treated only with MDMA.

CONCLUSIONS

Ethanol and MDMA co-administration increases the neurobehavioural changes induced by the consumption of each one of these drugs. However, as ethanol consumption did not increase neuroinflammatory responses induced by MDMA, other mechanisms, mediated by ethanol, are likely to account for this effect and need to be evaluated.

Adolescent pre-exposure to ethanol and 3,4-methylenedioxymethylamphetamine (MDMA) increases conditioned rewarding effects of MDMA and drug-induced reinstatement

Many adolescents often take ethanol (EtOH) in combination with 3,4-methylenedioxymethylamphetamine (MDMA). In the present work, we used a mouse model to study the effect of repeated pre-exposure during adolescence to EtOH (2 g/kg), MDMA (10 or 20 mg/kg) or EtOH + MDMA on the rewarding and reinstating effects of MDMA in the conditioned place preference (CPP) paradigm. Pre-exposure to EtOH, MDMA or both increased the rewarding effects of a low dose of MDMA (1.25 mg/kg). These pre-treatments did not affect the acquisition of the CPP induced by 5 mg/kg of MDMA. However, the CPP was more persistent in mice pre-exposed to both doses of MDMA or to EtOH + MDMA20. After extinction of the CPP induced by 5 mg/kg of MDMA, reinstatement was observed in all groups with a priming dose of 2.5 mg/kg of MDMA, in the groups pre-exposed to EtOH or MDMA alone with a priming dose of 1.25 mg/kg, and in the groups pre-treated with MDMA alone with a priming dose of 0.625 mg/kg. Pre-treatment during adolescence with MDMA or EtOH induced long-term changes in the level of biogenic amines [dihydroxyphenyl acetic acid, homovanillic acid, dopamine turnover, serotonin (5-hydroxytryptamine, 5-HT) and 5-hydroxyindole acetic acid (5-HIAA) in the striatum, and 5-HT and 5-HIAA in the cortex] after the first reinstatement test, although these effects depended on the dose used during conditioning. These results suggest that exposure to EtOH and MDMA during adolescence reinforces the addictive properties of MDMA.

Toxicity of amphetamines: an update

Amphetamines represent a class of psychotropic compounds, widely abused for their stimulant, euphoric, anorectic, and, in some cases, emphathogenic, entactogenic, and hallucinogenic properties. These compounds derive from the β-phenylethylamine core structure and are kinetically and dynamically characterized by easily crossing the blood-brain barrier, to resist brain biotransformation and to release monoamine neurotransmitters from nerve endings. Although amphetamines are widely acknowledged as synthetic drugs, of which amphetamine, methamphetamine, and 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) are well-known examples, humans have used natural amphetamines for several millenniums, through the consumption of amphetamines produced in plants, namely cathinone (khat), obtained from the plant Catha edulis and ephedrine, obtained from various plants in the genus Ephedra. More recently, a wave of new amphetamines has emerged in the market, mainly constituted of cathinone derivatives, including mephedrone, methylone, methedrone, and buthylone, among others. Although intoxications by amphetamines continue to be common causes of emergency department and hospital admissions, it is frequent to find the sophism that amphetamine derivatives, namely those appearing more recently, are relatively safe. However, human intoxications by these drugs are increasingly being reported, with similar patterns compared to those previously seen with classical amphetamines. That is not surprising, considering the similar structures and mechanisms of action among the different amphetamines, conferring similar toxicokinetic and toxicological profiles to these compounds. The aim of the present review is to give an insight into the pharmacokinetics, general mechanisms of biological and toxicological actions, and the main target organs for the toxicity of amphetamines. Although there is still scarce knowledge from novel amphetamines to draw mechanistic insights, the long-studied classical amphetamines-amphetamine itself, as well as methamphetamine and MDMA, provide plenty of data that may be useful to predict toxicological outcome to improvident abusers and are for that reason the main focus of this review.

Intermittent ethanol exposure increases long-lasting behavioral and neurochemical effects of MDMA in adolescent mice

RATIONALE

Heavy binge drinking is increasingly frequent among adolescents, while ethanol (EtOH) is often used in combination with 3,4-methylenedioxymethamphetamine (MDMA).

OBJECTIVES

The long-lasting effects of intermittent exposure to EtOH and MDMA during adolescence on motor activity, anxiety, and social behavior were evaluated in adult mice. The concentration of brain monoamines in the striatum, cortex, and hippocampus was measured following the behavioral test.

METHODS

Adolescent OF1 mice were exposed to ethanol (1.25 g/kg) on two consecutive days at 48-h intervals over a 14-day period (from PND 29 to 42). A total of eight injections of MDMA (10 or 20 mg/kg) were administered twice daily at 4-h intervals over two consecutive days, and this schedule was repeated 6 days later (PND 33, 34, 41, and 42). Behavioral tests and analysis of brain monoamines took place on PND 64 to 67.

RESULTS

Exposure to MDMA during adolescence increased the anxiogenic response in the elevated plus maze, with adult mice spending less time in the open arms of the maze and exhibiting lower concentrations of DA in the striatum. A pattern of ethanol administration modeling binge drinking during adolescence enhanced these effects and undermined the hyperthermic response induced by MDMA. Passive avoidance was affected only when EtOH was administered alone.

CONCLUSIONS

Juvenile administration of MDMA and alcohol was found to cause a decrease in monoamine levels in adulthood, as well as changes in social interaction behaviors, locomotor activity, increase measures of anxiety in the elevated plus maze (EPM), and decrease step-through latencies in passive avoidance test.

Effects of ethanol and ecstasy on conditioned place preference in the rat

The club drug ecstasy (3,4-methylenedioxymethylamphetamine or MDMA) is often taken recreationally with ethanol (EtOH). We have shown previously that EtOH potentiates the psychomotor effects of MDMA in rats. More recently, we demonstrated in striatal slices that MDMA produced preferential release of serotonin, but when combined with EtOH, the preferential release shifted to dopamine, raising the possibility that administration of EtOH may increase the reward effect of MDMA. To address this possibility, adult male Long-Evans rats were tested for conditioned place preference following treatment with saline, EtOH (0.75 g/kg), MDMA (6.6 mg/kg) or the combination. The only condition that produced a preference for the compartment associated with the drug was that of the drug combination. The current data are in line with anecdotal reports and one study in humans, indicating that EtOH alters the pharmacological effects of MDMA including self reports of enhanced or prolonged euphoria. Thus, administration of EtOH might increase the risk for compulsive use of MDMA, an issue that warrants further study.

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.

Ethanol increases the distribution of MDMA to the rat brain: possible implications in the ethanol-induced potentiation of the psychostimulant effects of MDMA

Ecstasy (3,4-methylenedioxymethylamphetamine; MDMA) is a popular club drug often taken with ethanol (EtOH). We recently found EtOH potentiated the psychomotor effects of MDMA in rats. This potentiation could reflect pharmacodynamic or/and pharmacokinetic processes. To test the latter hypothesis, rats were injected i.p. with 6.6 or 10 mg/kg MDMA with or without 1.5 g/kg EtOH, and were killed at 5, 15 or 60 min after injection. MDMA, its primary metabolite, 3,4-methylenedioxyamphetamine (MDA), and EtOH concentrations were determined in the plasma and the hippocampus, frontal cortex and striatum at each time-point. EtOH potentiated MDMA-induced hyperactivity mainly during the first 60 min post-administration. Fifteen and 60 min after treatment with MDMA and EtOH, MDMA concentrations were greater than after MDMA alone in the blood and the three brain regions examined. EtOH, however, did not increase the fraction of MDMA converted to MDA, as shown by unaltered MDA/MDMA ratios at either MDMA dose. Interestingly, when combined with EtOH, the distribution of MDMA and MDA in the brain was not homogeneous. Concentrations of both were much higher in the striatum and cortex, than in the hippocampus. Thus, at least part of the potentiation of the MDMA-induced hyperlocomotion by EtOH might be the result of a higher concentration of MDMA and metabolites in the blood and brain. Our results present clear evidence that EtOH increases brain and blood concentrations of MDMA and leads to the possibility of both enhanced MDMA-based neurotoxicity and increased liability for abuse.

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

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

Effects of ethanol and 3,4-methylenedioxymethamphetamine (MDMA) alone or in combination on spontaneous and evoked overflow of dopamine, serotonin and acetylcholine in striatal slices of the rat brain

Ethanol (EtOH) potentiates the locomotor effects of 3,4-methylenedioxymetamphetamine (MDMA) in rats. This potentiation might involve pharmacokinetic and/or pharmacodynamic mechanisms. We explored whether the latter could be local. Using a slice superfusion approach, we assessed the effects of MDMA (0.3, 3microm) and/or EtOH (2mm) on the spontaneous outflow and electrically evoked release of serotonin (5-HT), dopamine (DA) and acetylcholine (ACh) in the striatum, and for comparison, on 5-HT release in hippocampal and neocortical tissue. MDMA and less effectively EtOH, augmented the outflow of 5-HT in all regions. The electrically evoked 5-HT release was increased by MDMA at 3microm in striatal slices only. With nomifensine throughout, EtOH significantly potentiated the 0.3microm MDMA-induced outflow of 5-HT, but only in striatal slices. EtOH or MDMA also enhanced the spontaneous outflow of DA, but MDMA reduced the electrically evoked DA release. With fluvoxamine throughout superfusion, EtOH potentiated the effect of MDMA on the spontaneous outflow of DA. Finally, 3microm MDMA diminished the electrically evoked release of ACh, an effect involving several receptors (D2, 5-HT2, NMDA, nicotinic, NK1), with some interactions with EtOH. Among other results, we show for the first time a local synergistic interaction of EtOH and MDMA on the spontaneous outflow of striatal DA and 5-HT, which could be relevant to the EtOH-induced potentiation of hyperlocomotion in MDMA-treated rats. These data do not preclude the contribution of other pharmacodynamic and/or pharmacokinetic mechanisms in vivo but support the hypothesis that EtOH may affect the abuse liability of MDMA.

The relationship between core body temperature and 3,4-methylenedioxymethamphetamine metabolism in rats: implications for neurotoxicity

RATIONALE

A close relationship appears to exist between 3,4-methylenedioxymethamphetamine (MDMA)-induced changes in core body temperature and long-term serotonin (5-HT) loss.

OBJECTIVE

We investigated whether changes in core body temperature affect MDMA metabolism.

MATERIALS AND METHODS

Male Wistar rats were treated with MDMA at ambient temperatures of 15, 21.5, or 30 degrees C to prevent or exacerbate MDMA-induced hyperthermia. Plasma concentrations of MDMA and its main metabolites were determined for 6 h. Seven days later, animals were killed and brain indole content was measured.

RESULTS

The administration of MDMA at 15 degrees C blocked the hyperthermic response and long-term 5-HT depletion found in rats treated at 21.5 degrees C. At 15 degrees C, plasma concentrations of MDMA were significantly increased, whereas those of three of its main metabolites were reduced when compared to rats treated at 21.5 degrees C. By contrast, hyperthermia and indole deficits were exacerbated in rats treated at 30 degrees C. Noteworthy, plasma concentrations of MDMA metabolites were greatly enhanced in these animals. Instrastriatal perfusion of MDMA (100 microM for 5 h at 21 degrees C) did not potentiate the long-term depletion of 5-HT after systemic MDMA. Furthermore, interfering in MDMA metabolism using the catechol-O-methyltransferase inhibitor entacapone potentiated the neurotoxicity of MDMA, indicating that metabolites that are substrates for this enzyme may contribute to neurotoxicity.

CONCLUSIONS

This is the first report showing a direct relationship between core body temperature and MDMA metabolism. This finding has implications on both the temperature dependence of the mechanism of MDMA neurotoxicity and human use, as hyperthermia is often associated with MDMA use in humans.

Cellular and molecular mechanisms involved in the neurotoxicity of opioid and psychostimulant drugs

Substance abuse and addiction are the most costly of all the neuropsychiatric disorders. In the last decades, much progress has been achieved in understanding the effects of the drugs of abuse in the brain. However, efficient treatments that prevent relapse have not been developed. Drug addiction is now considered a brain disease, because the abuse of drugs affects several brain functions. Neurological impairments observed in drug addicts may reflect drug-induced neuronal dysfunction and neurotoxicity. The drugs of abuse directly or indirectly affect neurotransmitter systems, particularly dopaminergic and glutamatergic neurons. This review explores the literature reporting cellular and molecular alterations reflecting the cytotoxicity induced by amphetamines, cocaine and opiates in neuronal systems. The neurotoxic effects of drugs of abuse are often associated with oxidative stress, mitochondrial dysfunction, apoptosis and inhibition of neurogenesis, among other mechanisms. Understanding the mechanisms that underlie brain dysfunction observed in drug-addicted individuals may contribute to improve the treatment of drug addiction, which may have social and economic consequences.

Interactions between ethanol and cocaine, amphetamine, or MDMA in the rat: thermoregulatory and locomotor effects

RATIONALE

(+/-)-3,4-methylenedioxymethamphetamine (MDMA, ecstasy) is often taken recreationally with ethanol (EtOH). In rats, EtOH may potentiate MDMA-induced hyperactivity, but attenuate hyperthermia.

OBJECTIVE

Experiment 1 compared the interactions between EtOH (1.5 g/kg) and MDMA (6.6 mg/kg) with EtOH + cocaine (COCA; 10 mg/kg) and EtOH + amphetamine (AMPH; 1 mg/kg) on locomotor activity and thermoregulation. Experiment 2 used a weaker dose of MDMA (3.3 mg/kg) and larger doses of COCA (20 mg/kg) and AMPH (2 mg/kg).

MATERIALS AND METHODS

Drug treatments were administered on four occasions (2, 5, and 2 days apart, respectively; experiment 1) or two (2 days apart; experiment 2).

RESULTS

All psychostimulants increased activity, and EtOH markedly increased the effect of MDMA. AMPH alone-related hyperactivity showed modest sensitization across treatment days, while MDMA + EtOH activity showed marked sensitization. AMPH, COCA, and MDMA induced hyperthermia of comparable amplitude (+1 to +1.5 degrees C). Co-treatment with EtOH and AMPH (1 mg/kg) or COCA (10 mg/kg) produced hypothermia greater than that produced by EtOH alone. Conversely, EtOH attenuated MDMA-related hyperthermia, an effect increasing across treatment days. These results demonstrate that the interaction between MDMA and EtOH may be different from the interaction between EtOH and AMPH or COCA.

CONCLUSION

Because of potential health-related consequences of such polydrug misuse, it is worth identifying the mechanisms underlying these interactions, especially between EtOH and MDMA. Given the different affinity profiles of the three drugs for serotonin, dopamine, and norepinephrine transporters, our results appear compatible with the possibility of an important role of serotonin in at least the EtOH-induced potentiation of MDMA-induced hyperlocomotion.

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

RATIONALE

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

OBJECTIVE

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

RESULTS

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

CONCLUSIONS

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

Ethanol–ecstasy (MDMA) interactions in rats: Preserved attenuation of hyperthermia and potentiation of hyperactivity by ethanol despite prior ethanol treatment

Recreational use of ecstasy, or (+/-)-3,4-methylenedioxymethamphetamine (MDMA), is often associated with other drugs, among which ethanol is one of the most common. Little is known, however, about the interaction between these two drugs. Using a daily ethanol and/or MDMA administration regimen, we recently showed that ethanol potentiated the hyperactivity (in the home cage), but attenuated the hyperthermia induced by MDMA. The prevention of hyperthermia occurred only on the first of four daily ethanol-MDMA treatments, indicating possible tolerance to ethanol. In order to test the tolerance hypothesis, we treated Long-Evans adult male rats with ethanol on 4 consecutive days prior to their first treatment with MDMA-ethanol. Our results first confirmed that ethanol (1.5 g/kg, i.p.) potentiates the psychomotor effects of MDMA (10 mg/kg, i.p.), while attenuating its pyretic effects (6.6 mg/kg, i.p.). The results also showed that both the potentiation of locomotor activity and the attenuation of hyperthermia by ethanol are not at all altered by prior ethanol treatment. This indicates that tolerance to ethanol per se does not account for what appears to be tolerance to the ethanol-MDMA combination, thus indicating that ethanol-MDMA combination likely has unique pharmacological effects.

A review of acute effects of 3,4-methylenedioxymethamphetamine in healthy volunteers

This review of the literature aims to identify the acute effects of MDMA (ecstasy) in healthy volunteers. The wide range of relevant but methodologically diverse tests was .rst grouped into clusters to allow an evaluation of tests that would otherwise have been excluded due to their low frequency of utilization. The following three types of tests were evaluated: (1) functional tests quantifying executive, attention, visual, motor, visuomotor and auditory functions, (2) phenomenological tests assessing personal, subjective experiences, and (3) physiological measures reflecting neurophysiological, endocrine and physiological parameters. MDMA showed robust effects on most of the phenomenological and physiological tests. Functional tests were scarce, preventing any meaningful conclusions to be drawn from their evaluation other than that these tests should be incorporated into future acute-effect studies. A striking doseñresponse relationship appeared for cardiovascular effects. At doses below 1.0 mg/kg MDMA no change was observed relative to placebo while above this dose all studies reported significant increases. Furthermore, pupil size, plasma cortisol and plasma prolactin levels proved responsive to MDMA administration. The reported subjective effects of MDMA matched the entactogenic profile. Although interest in the action of MDMA is considerable, the existing knowledge about the cognitive effects of MDMA in humans is still rather limited and further research into the drug's effects is recommended, also in view of potential therapeutic uses of the drug.

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

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

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

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

Age-dependent (+)MDMA-mediated Neurotoxicity in Mice

In the present study the effects of a neurotoxic regimen of (+)-MDMA (20 mg/kgx4, s.c.) in 4- and 10-week-old C57Bl/6J mice during treatment and 7 days post-treatment were examined. Rectal temperatures monitored between (+)-MDMA injections (30 min post-injection/2 h intervals) revealed hyperthermic responses in both age groups, with the magnitude of the response significantly greater in older mice. Seven days post-treatment, immunoblot analyses of the vesicular monoamine transporter 2 (VMAT2), and tyrosine hydroxylase (TH) revealed significant reductions (-37 and -58%, respectively) in the older animals, but not in the younger group, compared to age-matched controls. Dopamine transporter (DAT) expression was significantly reduced in both 4- and 10-week-old animals (26 and 69.7%, respectively). (+)-MDMA-treated animals also exhibited significantly lower levels of striatal dopamine, and 3,4-dihydroxyphenylacetic acid than controls, again the effect being more pronounced in the older animals. Although both age groups showed evidence of (+)-MDMA-induced toxicity, our data revealed that older animals exhibited a greater hyperthermic response to (+)-MDMA and were also are more susceptible to subsequent dopaminergic damage than the younger animals.

Ethanol, 3,4-methylenedioxymethamphetamine (ecstasy) and their combination: long-term behavioral, neurochemical and neuropharmacological effects in the rat

This study investigated long-term behavioral, neurochemical, and neuropharmacological effects of ethanol-(+/-)-3,4-methylenedioxymethamphetamine (MDMA, ecstasy) combinations. Over 4 consecutive days, male Long-Evans rats received 1.5 g/kg ethanol and/or 10 mg/kg MDMA, or saline. Rectal temperatures were taken in some rats. Starting 4 days after the last injection, we tested working memory, sensory-motor coordination, and anxiety. Subsequently, we measured cortical, striatal, septal, and hippocampal monoamines (last MDMA injection-euthanasia delay: 20 days), or electrically evoked release of serotonin (5-HT) in cortical and hippocampal slices, and its modulation in the presence of CP 93,129 (3-(1,2,5,6-tetrahydropyrid-4-yl)pyrrollo[3,2-b]pyrid-5-one) or methiotepin (last MDMA injection-euthanasia delays: 3-6 weeks). Ethanol attenuated the MDMA-induced hyperthermia, but only on the first day. In the long-term, MDMA reduced 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) content in most brain regions. The behavioral and neurochemical effects of the ethanol-MDMA combination were comparable to those of MDMA alone; sensory-motor coordination was altered after ethanol and/or MDMA. In hippocampal slices from rats given ethanol and MDMA, the CP 93,129-induced inhibition and methiotepin-induced facilitation of 5-HT release were stronger and weaker, respectively, than in the other groups. This is the first study addressing long-term effects of repeated MDMA and EtOH combined treatments in experimental animals. Whereas the drug combination produced the same behavioral and neurochemical effects as MDMA alone, our neuropharmacological results suggest that MDMA-EtOH interactions may have specific long-term consequences on presynaptic modulation of hippocampal 5-HT release, but not necessarily related to MDMA-induced depletion of 5-HT. Thus, it is likely that the psycho(patho)logical problems reported by ecstasy users drinking alcohol are not solely due to the consumption of MDMA.

Microglial activation is a pharmacologically specific marker for the neurotoxic amphetamines

Neurotoxic amphetamines cause damage to monoamine nerve terminals of the striatum by unknown mechanisms. Microglial activation contributes to the neuronal damage that accompanies injury, disease, and inflammation, but a role for these cells in amphetamine-induced neurotoxicity has received little attention. We show presently that D-methamphetamine, 3,4-methylenedioxymethamphetamine (MDMA), D-amphetamine, and p-chloroamphetamine, each of which has been linked to dopamine (DA) or serotonin nerve terminal damage, result in microglial activation in the striatum. The non-neurotoxic amphetamines l-methamphetamine, fenfluramine, and DOI do not have this effect. All drugs that cause microglial activation also increase expression of glial fibrillary acidic protein (GFAP). At a minimum, microglial activation serves as a pharmacologically specific marker for striatal nerve terminal damage resulting only from those amphetamines that exert neurotoxicity. Because microglia are known to produce many of the reactive species (e.g., nitric oxide, superoxide, cytokines) that mediate the neurotoxicity of the amphetamine-class of drugs, their activation could represent an early and essential event in the neurotoxic cascade associated with high-dose amphetamine intoxication.

Serotonin neurotoxins--past and present

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