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

Ventral striatum regulates behavioral response to ethanol and MDMA combination

Our previous studies consistently showed that MDMA-induced locomotor hyperactivity is dramatically increased by coadministration of ethanol (EtOH) in rats, indicating possible potentiation of MDMA abuse liability. Thus, we aimed to identify the brain region(s) and neuropharmacological substrates involved in the pharmacodynamics of this potentiation. We first showed that potentiation of locomotor activity by the combination of ip administration of EtOH (1.5 g/kg) and MDMA (6.6 mg/kg) is delay sensitive and maximal when both drugs are injected simultaneously. Then, we used the 2-deoxyglucose quantitative autoradiography technique to assess the impact of EtOH, MDMA, or their combination on local cerebral metabolic rates for glucose (CMRglcs). We showed a specific metabolic activation in the ventral striatum (VS) under MDMA + EtOH versus MDMA or EtOH alone. We next tested if reversible (tetrodotoxin, TTX) or permanent (6-hydrodoxyopamine, 6-OHDA) lesion of the VS could affect locomotor response to MDMA and MDMA + EtOH. Finally, we blocked dopamine D1 or glutamate NMDA receptors in the VS and measured the effects of MDMA and MDMA + EtOH on locomotor activity. We showed that bilateral reversible inactivation (TTX) or permanent lesion (6-OHDA) of the VS prevented the potentiation by EtOH of MDMA-induced locomotor hyperactivity. Likewise, blockade of D1 or NMDA receptors in the VS also reduced the potentiation of MDMA locomotor activity by EtOH. These data indicate that dopamine D1 and glutamate NMDA receptor-driven mechanisms in the VS play a key role in the pharmacodynamics of EtOH-induced potentiation of the locomotor effects of MDMA.

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.

Conditioned Reward of Opioids, but not Psychostimulants, is Impaired in GABA-A Receptor δ Subunit Knockout Mice

Extrasynaptic δ subunit-containing γ-aminobutyric acid type A receptors (δ-GABA_A Rs) are emerging as targets for a number of neuropsychopharmacological drugs, including the direct GABA site agonist gaboxadol and neuroactive steroids. Among other regions, these δ-GABA_A Rs are functionally expressed in the ventral tegmental area (VTA), the cell body region of mesocorticolimbic dopamine (DA) system important for motivated behaviours, and in the target region, the nucleus accumbens. Gaboxadol and neurosteroids induce VTA DA neuron plasticity ex vivo, by inhibiting the VTA GABA neurons, and aversive place conditioning, which are absent in the δ-GABA_A R knockout mice (δ-KO). It is not known whether δ-GABA_A Rs are important for the effects of other drugs, such as opioids (that also inhibit GABA neurons) and stimulants (that primarily elevate monoamine levels). Here, we used δ-KO mice and conditioned place preference (CPP) test to study the rewarding effects of morphine (20 mg/kg), methamphetamine (1 mg/kg) and mephedrone (5 mg/kg). Morphine-induced nociception was also assessed using tail-flick and hot-plate tests. We found that the δ-KO mice failed to express morphine-induced CPP, but that they were more sensitive to morphine-induced analgesia in the tail-flick test. In contrast, stimulant-induced CPP in the δ-KO mice was similar to that in the wild-type controls. Thus, the conditioned rewarding effect by opioids, but not that of stimulants, was impaired in the absence of δ-GABA_A Rs. Further studies are warranted to assess the potential of δ-GABA_A R antagonists as possible targets for reducing morphine reward and potentiating morphine analgesia.

Effect of the combination of mephedrone plus ethanol on serotonin and dopamine release in the nucleus accumbens and medial prefrontal cortex of awake rats

Cathinones, such as mephedrone (Meph), are often co-abused with alcoholic drinks. In the present study, we investigated the combined effects of Meph plus ethanol (EtOH) on neurotransmitter release in the nucleus accumbens (NAc) and the medial prefrontal cortex (mPFC). A guide canula was stereotaxically implanted into either the NAc or the mPFC of male Sprague-Dawley rats. Seven days after surgery, a microdialysis probe was inserted and rats were administered saline, EtOH (1 g/kg, i.p.), Meph (25 mg/kg, s.c.), or their combination, and dialysates were collected. Serotonin (5-HT), dopamine (DA), and their metabolites (5-HIAA, DOPAC and HVA) were determined through high-pressure liquid chromatography coupled to mass spectrometry. 5-HT and DA peaked 40 min after Meph administration (with or without EtOH co-treatment) in both areas. EtOH combined with Meph increased the 5-HT release compared with the rats receiving Meph alone (85% in NAc, 65% in mPFC), although the overall change in the area under the curve only reached statistical significance in the NAc. In mPFC, the increased release of 5-HT lasted longer in the combination than that in the Meph group. Moreover, EtOH potentiated the psychostimulant effect of Meph measured as a locomotor activity. Given that both 5-HT and DA are also related with reward and impulsivity, the observed effects point to an increased risk of abuse liability when combining Meph with EtOH compared with consuming these drugs alone.

Concentrations of MDPV in rat striatum correlate with the psychostimulant effect

3,4-methylenedioxypyrovalerone or MDPV is a synthetic cathinone with psychostimulant properties more potent than cocaine. We quantified this drug in the striatum after subcutaneous administration to rats. MDPV reached the brain around 5 min after its administration and peaked at 20-25 min later. The elimination half-life in the striatum (61 min) correlates with the decrease in the psychostimulant effect after 60 min. Around 11% of the administered dose reached the striatum and, considering a homogeneous brain distribution, we determined that around 86% of the plasma MDPV is distributed to the brain. MDPV induced a dose-dependent increase in locomotor activity, rearing behaviour and stereotypies, all prevented by haloperidol. A plot of locomotor activity or stereotypies versus MDPV striatal concentrations over time showed a direct relationship between factors. No free MDPV metabolites were detected in plasma, at any time, but hydrolysis with glucuronidase allowed us to identify mainly three metabolites, one of them for the first time in rat plasma. The present results contribute to evidence that MDPV induces hyperlocomotion mainly through a dopamine-dependent mechanism. Good correlation between behavioural effects and striatal levels of MDPV leads us to conclude that its psychostimulant effect is mainly due to a striatal distribution of the substance. The present research provides useful information on the pharmacokinetics of MDPV, and can help design new experiments with kinetics data as well as provide a better understanding of the effects of MDPV in humans and its potential interactions.

Alcohol enhances the psychostimulant and conditioning effects of mephedrone in adolescent mice; postulation of unique roles of D3 receptors and BDNF in place preference acquisition

BACKGROUND AND PURPOSE

The psychostimulant mephedrone is often consumed in combination with alcohol (EtOH). This kind of drug consumption during adolescence is a matter of concern.

EXPERIMENTAL APPROACH

We studied, in adolescent CD-1 mice, whether EtOH could enhance the psychostimulant (locomotor acivity) and rewarding [conditioned place preference (CPP)] effects of mephedrone. We also determined the transcriptional changes associated with a conditioning treatment with these drugs.

KEY RESULTS

Mephedrone (10 mg·kg(-1)) increased locomotor activity, which was further enhanced by 40% when combined with EtOH (1 g·kg(-1)). This enhancement was blocked by haloperidol. Furthermore, mephedrone (25 mg·kg(-1)) induced CPP, which increased by 70% when administered with a dose of EtOH that was not conditioning by itself (0.75 g·kg(-1)). There was enhanced expression of the D3 dopamine receptor mRNA (Drd3) and Arpc5 in all drug-treated groups. The D3 receptor antagonist SB-277011A and the BDNF receptor antagonist ANA-12 completely prevented CPP as well as the increases in Drd3 in all groups. Accordingly, increased expression of BDNF mRNA in medial prefrontal cortex was detected at 2 and 4 h after mephedrone administration.

CONCLUSIONS AND IMPLICATIONS

If translated to humans, the enhancement of mephedrone effects by ethanol could result in increased abuse liability. D3 receptors and BDNF play a key role in the establishment of CPP by mephedrone, although an accompanying increase in other synaptic plasticity-related genes may also be necessary.

Pharmacology should be at the centre of all preclinical and clinical studies on new psychoactive substances (recreational drugs)

Despite the publication of a substantial body of preclinical and clinical information on recent recreational drugs such as 3,4-methylenedioxymethamphetamine (MDMA, 'ecstasy') and cathinone compounds such as mephedrone there remains a disturbing lack of consensus as to how dangerous these compounds are to the health of the individual and to society in general. This perspective proposes that use of good pharmacological practice should be mandatory in all preclinical and clinical studies. Its use will assist both translation and reverse translation of information produced in animals and clinical subjects. We propose several basic rules to be followed in all future studies. Preclinical studies should employ pharmacokinetic-pharmacodynamic integration thereby exposing animals to known or calculable drug concentrations. This will provide results relevant to pharmacology rather than toxicology and, crucially, data relevant to human drug use. Full experimental detail should be routinely provided, to allow comparison with other similar work. In clinical studies evidence should be provided that the drug under investigation has been ingested by the subjects being examined, and details given of all other drugs being ingested. Drug-drug interactions are an unavoidable confound but studies of a size that allows reliable statistical evaluation and preferably allows sub-group analysis, particularly by using meta-analysis, should help with this problem. This may require greater collaboration between investigative groups, as routinely occurs during pharmaceutical clinical trials. Other proposals include greater integration of preclinical and clinical scientists in both preclinical and clinical studies and changes in the law regarding Good Manufacturing Process (GMP) sourcing of drug for human studies.

Simultaneous polysubstance use among Danish 3,4-methylenedioxymethamphetamine and hallucinogen users: combination patterns and proposed biological bases

OBJECTIVE

To describe patterns of simultaneous polysubstance use (SPU) among Danish 3,4-methylenedioxymethamphetamine (MDMA) ("Ecstasy") and hallucinogen users.

METHODS

A cross-sectional survey of 98 active MDMA and/or hallucinogen users recruited through homepage advertisements, flyers, and word of mouth in Denmark. Lifetime and recent substance use and SPU at last recalled use was described by structured interviews. Hair samples from a subset of participants were analyzed for MDMA.

RESULTS

The participants had used an average of 12.6 (95% confidence interval: 11.7-13.4) psychoactive substances during their lifetime. SPU was prevalent among MDMA, d-lysergic acid diethylamide (LSD), and psilocybin users, in particular with alcohol and cannabis. Among MDMA users, 69% had combined MDMA with amphetamines, 56% with hallucinogens, and 47% with cocaine. At last recalled use, MDMA was taken with 2.1 ± 1.2 substances in 32 different combinations. The participants preferred specific drug combinations and named several, which in their experience enhanced or counteracted each other. Alcohol and cannabis were typically used before, during, and after MDMA, LSD, and psilocybin, whereas amphetamines were predominantly taken before these substances. When LSD was combined with MDMA, the majority took MDMA after LSD.

CONCLUSIONS

Simultaneous polysubstance use was common among Danish MDMA and hallucinogen users, and patterns of preferred substance combinations were evident.

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.

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.

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.

Increased effects of 3,4-methylenedioxymethamphetamine (ecstasy) in a rat model of depression

3,4-Methylenedioxymethamphetamine (MDMA, ecstasy) is associated with increases in core body temperature (T(C)) and depressive mood states in users. Flinders Sensitive Line (FSL) rats represent a rat model of depression originally bred from Sprague-Dawley (SD) rats. They are more sensitive to both muscarinic and serotonergic agonists and have altered thermoregulatory responses to various drugs. To examine the link between MDMA and depression, eight FSL and eight SD rats were administered saline and 5 and 7.5 mg/kg MDMA. Immediately following administration, rats were confined to an area with an ambient temperature (T(A)) of 30 ± 1°C for 30 minutes before being allowed access to a thermal gradient for four hours. The brains were removed one week after final dose of MDMA and concentrations of serotonin and dopamine were measured. Treatment with MDMA at both doses led to a higher T(C) in the FSL rats than the SD rats at high T(A) (P < 0.01). Fatalities due to hyperthermia occurred in the FSL rats after both doses, whereas all but one of the SD rats recovered well. Heart rate was also much higher after MDMA in the FSL rats throughout the experiments. The FSL rats showed significant decreases in all transmitters measured (P < 0.05). These differences between strains were not accounted for by altered blood or brain concentrations of MDMA. The results indicate that the FSL rats may be more susceptible to developing MDMA-induced hyperthermia and possible damage to the brain. These findings may be of importance to human users of MDMA who also have depression.

Mechanisms of MDMA (ecstasy)-induced oxidative stress, mitochondrial dysfunction, and organ damage

Despite numerous reports about the acute and sub-chronic toxicities caused by MDMA (3,4-methylenedioxymethamphetamine, ecstasy), the underlying mechanism of organ damage is poorly understood. The aim of this review is to present an update of the mechanistic studies on MDMA-mediated organ damage partly caused by increased oxidative/nitrosative stress. Because of the extensive reviews on MDMA-mediated oxidative stress and tissue damage, we specifically focus on the mechanisms and consequences of oxidative-modifications of mitochondrial proteins, leading to mitochondrial dysfunction. We briefly describe a method to systematically identify oxidatively-modified mitochondrial proteins in control and MDMA-exposed rats by using biotin-N-maleimide (biotin-NM) as a sensitive probe for oxidized proteins. We also describe various applications and advantages of this Cys-targeted proteomics method and alternative approaches to overcome potential limitations of this method in studying oxidized proteins from MDMA-exposed tissues. Finally we discuss the mechanism of synergistic drug-interaction between MDMA and other abused substances including alcohol (ethanol) as well as application of this redox-based proteomics method in translational studies for developing effective preventive and therapeutic agents against MDMA-induced organ damage.

Neurotoxicity and persistent cognitive deficits induced by combined MDMA and alcohol exposure in adolescent rats

Recent trend assessments of drug consumption reveal an increase in the simultaneous use of several drugs at raves, clubs and college settings among youngsters and young adults. We studied in adolescent rats the effects of repeated exposure to cocaine and 3,4-methylenedioxymethanphetamine (MDMA, ecstasy), given alone or in combination with alcohol, on memory performance, adult hippocampal neurogenesis and neurotoxicity. Rats were trained two weeks after the drug treatments in the radial arm maze. The results showed that only rats exposed to combinations of alcohol and MDMA exhibited significant memory deficits. Alcohol, MDMA and combinations thereof significantly decreased 5-bromodeoxyuridine labeling in the dentate gyrus (DG), indicating reduced survival of neuronal precursors. None of the treatments altered the length of the dendritic arbors of doublecortin (DCX)-positive neurons or the number and length of DCX-negative gaps in the DG. Thus, changes in adult neurogenesis were not causally related to the cognitive alterations induced by the treatments. Only the combination of alcohol and MDMA significantly decreased the population of mature granule neurons in the DG and increased the presence of cluster of differentiation 11b+ reactive microglia in the bordering areas of the subgranular zone. Critically, memory impairment was correlated with granule cell depletion. These observations demonstrate that exposure to alcohol and MDMA during adolescence, at doses that do not provoke apparent cognitive impairment when given separately, causes neurotoxic alterations affecting the DG region as well as persistent memory deficits. The findings highlight the elevated risk associated with the concurrent recreational use of alcohol and MDMA.

The variety of ecstasy/MDMA users: results from the National Epidemiologic Survey on alcohol and related conditions

This study investigates the potential heterogeneity of ecstasy or MDMA (3,4-methylenedioxy-N-methylamphetamine) users. Data came from the 2001-2002 National Epidemiologic Survey on Alcohol and Related Conditions (NESARC). Latent class analysis (LCA) and multinomial logistic regression procedures were used to identify subtypes of ecstasy users. Approximately 1.6% (n = 562) of adult participants (N = 43,093) reported lifetime ecstasy use. LCA identified three subtypes of ecstasy users. Class 1 exhibited pervasive use of most drug classes (ecstasy-polydrug users, 37%). Class 2 reported a high rate of use of marijuana and cocaine and a moderate use of amphetamines (ecstasy-marijuana-stimulant users, 29%). Class 3 was characterized by a high rate of use of marijuana and a low use of primarily prescription-type drugs (ecstasy-marijuana users, 34%). Subtypes were distinguished by family income, history of substance abuse treatment, and familial substance abuse. Class 1 exhibited the highest prevalence of disorders related to the use of marijuana (77%), tobacco (66%), amphetamines (36%), opioids (35%), sedatives (31%), and tranquilizers (30%). The recent resurgence in ecstasy use among adults underscores the need to monitor trends in its use.