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

Alcohol Co-Administration Changes Mephedrone-Induced Alterations of Neuronal Activity

Mephedrone (4-MMC), despite its illegal status, is still a widely used psychoactive substance. Its effects closely mimic those of the classical stimulant drug methamphetamine (METH). Recent research suggests that unlike METH, 4-MMC is not neurotoxic on its own. However, the neurotoxic effects of 4-MMC may be precipitated under certain circumstances, such as administration at high ambient temperatures. Common use of 4-MMC in conjunction with alcohol raises the question whether this co-consumption could also precipitate neurotoxicity. A total of six groups of adolescent rats were treated twice daily for four consecutive days with vehicle, METH (5 mg/kg) or 4-MMC (30 mg/kg), with or without ethanol (1.5 g/kg). To investigate persistent delayed effects of the administrations at two weeks after the final treatments, manganese-enhanced magnetic resonance imaging brain scans were performed. Following the scans, brains were collected for Golgi staining and spine analysis. 4-MMC alone had only subtle effects on neuronal activity. When administered with ethanol, it produced a widespread pattern of deactivation, similar to what was seen with METH-treated rats. These effects were most profound in brain regions which are known to have high dopamine and serotonin activities including hippocampus, nucleus accumbens and caudate-putamen. In the regions showing the strongest activation changes, no morphological changes were observed in spine analysis. By itself 4-MMC showed few long-term effects. However, when co-administered with ethanol, the apparent functional adaptations were profound and comparable to those of neurotoxic METH.

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.

A Systematic Review of the MDMA Model to Address Social Impairment in Autism

BACKGROUND

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterised by repetitive behaviours, cognitive rigidity/inflexibility, and social-affective impairment. Unfortunately, no gold-standard treatments exist to alleviate the core socio-behavioural impairments of ASD. Meanwhile, the prosocial empathogen/entactogen 3,4-methylene-dioxy-methamphetamine (MDMA) is known to enhance sociability and empathy in both humans and animal models of psychological disorders.

OBJECTIVE

We review the evidence obtained from behavioural tests across the current literature, showing how MDMA can induce prosocial effects in animals and humans, where controlled experiments were able to be performed.

METHODS

Six electronic databases were consulted. The search strategy was tailored to each database. Only English-language papers were reviewed. Behaviours not screened in this review may have affected the core ASD behaviours studied. Molecular analogues of MDMA have not been investigated.

RESULTS

We find that the social impairments may potentially be alleviated by postnatal administration of MDMA producing prosocial behaviours in mostly the animal model.

CONCLUSION

MDMA and/or MDMA-like molecules appear to be an effective pharmacological treatment for the social impairments of autism, at least in animal models. Notably, clinical trials based on MDMA use are now in progress. Nevertheless, larger and more extended clinical studies are warranted to prove the assumption that MDMA and MDMA-like molecules have a role in the management of the social impairments of autism.

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.

Cognitive Effects of MDMA in Laboratory Animals: A Systematic Review Focusing on Dose

±3,4-Methylenedioxymethamphetamine (MDMA) is a synthetic, psychoactive drug that is primarily used recreationally but also may have some therapeutic value. At low doses, MDMA produces feelings of relaxation, empathy, emotional closeness, and euphoria. Higher doses can produce unpleasant psychostimulant- and hallucinogen-like adverse effects and therefore are usually not taken intentionally. There is considerable evidence that MDMA produces neurotoxicity and cognitive deficits at high doses; however, these findings may not generalize to typical recreational or therapeutic use of low-dose MDMA. Here, we systematically review 25 years of research on the cognitive effects of MDMA in animals, with a critical focus on dose. We found no evidence that doses of less than 3 mg/kg MDMA-the dose range that users typically take-produce cognitive deficits in animals. Doses of 3 mg/kg or greater, which were administered most often and frequently ranged from 5 to 20 times greater than an average dose, also did not produce cognitive deficits in a slight majority of experiments. Overall, the preclinical evidence of MDMA-induced cognitive deficits is weak and, if anything, may be the result of unrealistically high dosing. While factors associated with recreational use such as polydrug use, adulterants, hyperthermia, and hyponatremia can increase the potential for neurotoxicity, the short-term, infrequent, therapeutic use of ultra low-dose MDMA is unlikely to pose significant cognitive risks. Future studies must examine any adverse cognitive effects of MDMA using clinically relevant doses to reliably assess its potential as a psychotherapeutic.

Differential Impact of Ad Libitum or Intermittent High-Fat Diets on Bingeing Ethanol-Mediated Behaviors

Background: Dietary factors have significant effects on the brain, modulating mood, anxiety, motivation and cognition. To date, no attention has been paid to the consequences that the combination of ethanol (EtOH) and a high-fat diet (HFD) have on learning and mood disorders during adolescence. The aim of the present work was to evaluate the biochemical and behavioral consequences of ethanol binge drinking and an HFD consumption in adolescent mice. Methods: Animals received either a standard diet or an HFD (ad libitum vs. binge pattern) in combination with ethanol binge drinking and were evaluated in anxiety and memory. The metabolic profile and gene expression of leptin receptors and clock genes were also evaluated. Results: Excessive white adipose tissue and an increase in plasma insulin and leptin levels were mainly observed in ad libitum HFD + EtOH mice. An upregulation of the Lepr gene expression in the prefrontal cortex and the hippocampus was also observed in ad libitum HFD groups. EtOH-induced impairment on spatial memory retrieval was absent in mice exposed to an HFD, although the aversive memory deficits persisted. Mice bingeing on an HFD only showed an anxiolytic profile, without other alterations. We also observed a mismatch between Clock and Bmal1 expression in ad libitum HFD animals, which were mostly independent of EtOH bingeing. Conclusions: Our results confirm the bidirectional influence that occurs between the composition and intake pattern of a HFD and ethanol consumption during adolescence, even when the metabolic, behavioral and chronobiological effects of this interaction are dissociated.

Cognitive and neurobehavioral benefits of an enriched environment on young adult mice after chronic ethanol consumption during adolescence

Binge drinking (BD) is a common pattern of ethanol (EtOH) consumption by adolescents. The brain effects of the acute EtOH exposure are well-studied; however, the long-lasting cognitive and neurobehavioral consequences of BD during adolescence are only beginning to be elucidated. Environmental enrichment (EE) has long been known for its benefits on the brain and may serve as a potential supportive therapy following EtOH exposure. In this study, we hypothesized that EE may have potential benefits on the cognitive deficits associated with BD EtOH consumption. Four-week-old C57BL/6J male mice were exposed to EtOH following an intermittent 4-day drinking-in-the-dark procedure for 4 weeks. Then they were exposed to EE during EtOH withdrawal for 2 weeks followed by a behavioral battery of tests including novel object recognition, novel location, object-in-place, rotarod, beam walking balance, tail suspension, light-dark box and open field that were run during early adulthood. Young adult mice exposed to EE significantly recovered recognition, spatial and associative memory as well as motor coordination skills and balance that were significantly impaired after adolescent EtOH drinking with respect to controls. No significant permanent anxiety or depressive-like behaviors were observed. Taken together, an EE exerts positive effects on the long-term negative cognitive deficits as a result of EtOH consumption during adolescence.

Animal Models of Early-Life Adversity

From the prenatal period throughout the first years of life, the brain undergoes its most rapid development, a period during which it is highly sensitive to external experiences. The timing of brain development differs from one region to another, as it also differs between substrates, neurotransmitter systems, and central endocrine circuitries. These discontinuities are part of the "critical periods of brain development." Early-life adversity (ELA), such as exposure to infection, maternal deprivation, and substance use, disrupts the programmed brain development, yielding a myriad of deviations in brain circuitry, stress responsivity, cognitive function, and general health. This is applicable to both humans and animal models.In our laboratory, several experimental animal designs have been developed that allow investigating the long-lasting consequences of ELA on brain function, cognitive and emotional development, and the risk to develop stress-related psychopathology later in adulthood. This book chapter will provide a review of such animal models, in particular, designs related to infections (LPS-induced), the quality of mother-infant relationship (maternal deprivation and separation), and substance use (ethanol intoxication). The behavior tests, biochemical, and immunohistochemistry assays applied after ELA will be explained. The behavioral tests encompass the open-field, elevated plus maze, forced swim, sucrose preference, Y-maze, object recognition, and Morris water maze tests. These experiments allow the assessment of several outcomes of interest, pertaining to locomotor activity, anxiety-like symptoms, depressive-like symptoms, working memory, recognition memory, spatial memory, and learning performance. The biochemical assays are employed to measure the level of oxidative stress and inflammation in brain areas after application of adversity. Immunohistochemistry puts into perspective the degree of immunoreactivity in the brain subjected to adversity. The findings from our laboratory indicate that the nature and timing of exposure play a critical role in sensitivity to develop neurodevelopmental disorders.

Neuroadaptive changes and behavioral effects after a sensitization regime of MDPV

3,4-methylenedioxypyrovalerone (MDPV) is a synthetic cathinone with cocaine-like properties. In a previous work, we exposed adolescent mice to MDPV, finding sensitization to cocaine effects, and a higher vulnerability to cocaine abuse in adulthood. Here we sought to determine if such MDPV schedule induces additional behavioral-neuronal changes that could explain such results. After MDPV treatment (1.5 mg kg^-1, twice daily, 7 days), mice were behaviorally tested. Also, we investigated protein changes in various brain regions. MDPV induced aggressiveness and anxiety, but also contributed to a faster habituation to the open field. This feature co-occurred with an induction of ΔFosB in the orbitofrontal cortex that was higher than its expression in the ventral striatum. Early after treatment, D2R:D1R ratio pointed to a preponderance of D1R but, upon withdrawal, the ratio recovered. Increased expression of Arc, CDK5 and TH, and decrease in DAT protein levels persisted longer after withdrawal, pointing to a neuroplastic lasting effect similar to that involved in cocaine addiction. The implication of the hyperdopaminergic condition in the MDPV-induced aggressiveness cannot be ruled out. We also found an initial oxidative effect of MDPV, without glial activation. Moreover, although initially the dopaminergic signal induced by MDPV resulted in increased ΔFosB, we did not observe any change in NFκB or GluA2 expression. Finally, the changes observed after MDPV treatment could not be explained according to the autoregulatory loop between ΔFosB and the epigenetic repressor G9a described for cocaine. This provides new knowledge about the neuroadaptive changes involved in the vulnerability to psychostimulant addiction.

Differential effects of MDMA and cocaine on inhibitory avoidance and object recognition tests in rodents

INTRODUCTION

Drug addiction continues being a major public problem faced by modern societies with different social, health and legal consequences for the consumers. Consumption of psychostimulants, like cocaine or MDMA (known as ecstasy) are highly prevalent and cognitive and memory impairments have been related with the abuse of these drugs.

AIM

The aim of this work was to review the most important data of the literature in the last 10 years about the effects of cocaine and MDMA on inhibitory avoidance and object recognition tests in rodents.

DEVELOPMENT

The object recognition and the inhibitory avoidance tests are popular procedures used to assess different types of memory. We compare the effects of cocaine and MDMA administration in these tests, taking in consideration different factors such as the period of life development of the animals (prenatal, adolescence and adult age), the presence of polydrug consumption or the role of environmental variables. Brain structures involved in the effects of cocaine and MDMA on memory are also described.

CONCLUSIONS

Cocaine and MDMA induced similar impairing effects on the object recognition test during critical periods of lifetime or after abstinence of prolonged consumption in adulthood. Deficits of inhibitory avoidance memory are observed only in adult rodents exposed to MDMA. Psychostimulant abuse is a potential factor to induce memory impairments and could facilitate the development of future neurodegenerative disorders.

Adolescent but not adult ethanol binge drinking modulates cocaine withdrawal symptoms in mice

Background

Ethanol (EtOH) binge drinking is an increasingly common behavior among teenagers that induces long-lasting neurobehavioral alterations in adulthood. An early history of EtOH abuse during adolescence is highly correlated with cocaine addiction in adulthood. Abstinence of cocaine abuse can cause psychiatric symptoms, such as anxiety, psychosis, depression, and cognitive impairments. This study assessed the consequences of adolescent exposure to EtOH on the behavioral alterations promoted by cocaine withdrawal in adulthood.

Methods

We pretreated juvenile (34–47 days old) or adult (68–81 days old) mice with EtOH (1.25 g/kg) following a binge-drinking pattern. Then, after a three-week period without drug delivery, they were subjected to a chronic cocaine treatment in adulthood and tested under cocaine withdrawal by the ensuing paradigms: open field, elevated plus maze, prepulse inhibition, tail suspension test, and object recognition. Another set of mice were treated with the same EtOH binge-drinking procedure during adolescence and were tested immediately afterwards under the same behavioral paradigms.

Results

Adolescent EtOH pretreatment undermined the anxiogenic effects observed after cocaine abstinence, reduced prepulse inhibition, and increased immobility scores in the tail suspension test following cocaine withdrawal. Moreover, the memory deficits evoked by these substances when given separately were enhanced in cocaine-withdrawn mice exposed to EtOH during adolescence. EtOH binge drinking during adolescence also induced anxiety, depressive symptoms, and memory impairments when measured immediately afterwards. In contrast, neither EtOH nor cocaine alone or in combination altered any of these behaviors when given in adulthood.

Conclusions

EtOH binge drinking induces short- and long-term behavioral alterations and modulates cocaine withdrawal symptoms when given in adolescent mice.

Alcohol Interactions with Psychostimulants: An Overview of Animal and Human Studies

Alcohol consumption with psychostimulants is very common among drug addicts. There is little known about the possible pharmacological interactions between alcohol and psychostimulants. Among most commonly co-abused psychostimulants with alcohol are methamphetamine, cocaine, 3,4-methylenedioxymethamphetaminen, and nicotine. Co-abuse of alcohol with psychostimulants can lead to several neurophysiological dysfunctions such as decrease in brain antioxidant enzymes, disruption of learning and memory processes, cerebral hypo-perfusion, neurotransmitters depletion as well as potentiation of drug seeking behaviour. Moreover, co-abuse of alcohol and psychostimulants can lead to increase in heart rate, blood pressure, myocardial oxygen consumption and cellular stress, and the risk of developing different types of cancer. Co-abuse of alcohol with psychostimulants during pregnancy can lead to fetal brain abnormalities. Further studies are needed to investigate the pharmacokinetics, pharmacodynamics, and neurochemical changes on co-abuse of alcohol and psychostimulants.

Role of CB2 receptors in social and aggressive behavior in male mice

RATIONALE

Male CB1KO mice exhibit stronger aggressive responses than wild-type mice.

OBJECTIVE

This study was designed to examine the role of cannabinoid CB2r in social and aggressive behavior.

METHODS

The social interaction test and resident-intruder paradigm were performed in mice lacking CB2r (CB2KO) and in wild-type (WT) littermates. The effects of the CB2r selective agonist JWH133 (1 and 2 mg/kg) on aggression were also evaluated in Oncins France 1 (OF1) mice. Gene expression analyses of monoamine oxidase-A (MAO-A), catechol-o-methyltransferase (COMT), 5-hydroxytryptamine transporter (5-HTT), and 5-HT1B receptor (5HT1Br) in the dorsal raphe nuclei (DR) and the amygdala (AMY) were carried out using real-time PCR.

RESULTS

Group-housed CB2KO mice exhibited higher levels of aggression in the social interaction test and displayed more aggression than resident WT mice. Isolation increased aggressive behavior in WT mice but did not affect CB2KO animals; however, the latter mice exhibited higher levels of social interaction with their WT counterparts. MAO-A and 5-HTT gene expression was significantly higher in grouped CB2KO mice. The expression of 5HT1Br, COMT, and MAO-A in the AMY was more pronounced in CB2KO mice than in WT counterparts. Acute administration of the CB2 agonist JWH133 significantly reduced the level of aggression in aggressive isolated OF1 mice, an effect that decreased after pretreatment with the CB2 receptor antagonist AM630.

CONCLUSION

Our results suggest that CB2r is implicated in social interaction and aggressive behavior and deserves further consideration as a potential new target for the management of aggression.

Sex differences in the long-lasting consequences of adolescent ethanol exposure for the rewarding effects of cocaine in mice

RATIONALE

The practice of binge drinking is very common among adolescents of both sexes. It can have long-term consequences with respect to drug consumption during adulthood, but knowledge on these effects in females is limited.

OBJECTIVES

The long-lasting effects of intermittent exposure to ethanol (EtOH) during adolescence on different cocaine-elicited behaviours, including locomotor reactivity, conditioned place preference (CPP) and intravenous self-administration, were evaluated in male and female adult mice. It was hypothesized that an EtOH binge during adolescence would increase sensitivity to the effects of a sub-threshold dose of cocaine and has a differential impact on the drug's effects in males and females.

METHODS

Adolescent OF1 mice (postnatal day (PND) 26) underwent a 2-week pre-treatment schedule consisting of 16 doses of EtOH (2.5 g/kg) or saline (twice daily administrations separated by a 4-h interval i.p.) administered on two consecutive days separated by an interval of 2 days. Three weeks later (PND > 60), we assessed locomotor activity responses induced by an acute injection of different doses of cocaine in experiment 1 and the rewarding effects of cocaine on the CPP (1 mg/kg) and intravenous self-administration (1 mg/kg/infusion) paradigms in experiment 2.

RESULTS

Pre-exposure to EtOH during adolescence altered motor reactivity to cocaine in a dose- and sex-dependent manner, increased sensitivity to cocaine in CPP and enhanced self-administration in adult mice.

CONCLUSIONS

The effects of intermittent exposure to ethanol during adolescence are evident in adulthood, during which greater sensitivity and intake of cocaine is observed and differ in each sex.

The novelty-seeking phenotype modulates the long-lasting effects of adolescent MDMA exposure

Exposure to drugs such as ethanol or cocaine during adolescence induces alterations in the central nervous system that are modulated by the novelty-seeking trait. Our aim was to evaluate the influence of this trait on the long-term effects of MDMA administration during adolescence on spontaneous behavior and conditioned rewarding effects in adulthood. Adolescent mice were classified as high or low novelty seekers (HNS or LNS) according to the hole-board test and received either MDMA (0, 10 or 20mg/kg PND 33-42) or saline. Three weeks later, having entered adulthood (PND>68), one set of mice performed the elevated plus maze and social interaction tests, while another set performed the conditioning place preference (CPP) test induced by cocaine-(1mg/kg) or MDMA-(1mg/kg). Only HNS mice treated with MDMA during adolescence acquired CPP in adulthood with a non-effective dose of cocaine or MDMA. Although it did not produce changes in motor activity, exposure to MDMA during adolescence was associated with more aggressive behaviors (threat and attack) and increased social contacts in HNS mice, while an anxiolytic effect was noted in LNS mice pre-treated with the highest dose of MDMA (20mg/kg). Administration of MDMA (10 or 20mg/kg) induced a decrease in DA levels in the striatum in LNS mice only and lower striatal serotonin levels in mice treated with the highest MDMA dose. Our findings show that adolescent MDMA exposure results in higher sensitivity to the conditioned reinforcing properties of MDMA and cocaine in adult HNS mice, which suggests that the relationship between exposure to MDMA in adolescence and a higher probability of substance is a feature of high novelty seekers only.

The novelty-seeking phenotype modulates the long-lasting effects of intermittent ethanol administration during adolescence

The aim of the present study was to investigate if a novelty-seeking phenotype mediates the long-lasting consequences of intermittent EtOH intoxication during adolescence. The hole board test was employed to classify adolescent mice as High- or Low-Novelty Seekers. Subsequently, animals were administered ethanol (1.25 or 2.5 g/kg) on two consecutive days at 48-h intervals over a 14-day period. Anxiety levels--measured using the elevated plus maze- spontaneous motor activity and social interaction test were studied 3 weeks later. A different set of mice underwent the same procedure, but received only the 2.5 g/kg dose of ethanol. Three weeks later, in order to induce CPP, the same animals were administered 1 or 6 mg/kg of cocaine or 1 or 2.5 mg/kg MDMA. The results revealed a decrease in aggressive behaviors and an anxiolytic profile in HNS mice and longer latency to explore the novel object by LNS mice. Ethanol exposure enhanced the reinforcing effects of cocaine and MDMA in both groups when CPP was induced with a sub-threshold dose of the drugs. The extinguished cocaine-induced CPP (1 and 6 mg/kg) was reinstated after a priming dose in HNS animals only. Our results confirm that intermittent EtOH administration during adolescence induces long-lasting effects that are manifested in adult life, and that there is an association between these effects and the novelty-seeking phenotype.

Adolescent binge-like ethanol exposure reduces basal α-MSH expression in the hypothalamus and the amygdala of adult rats

Melanocortins (MC) are central peptides that have been implicated in the modulation of ethanol consumption. There is experimental evidence that chronic ethanol exposure reduces α-MSH expression in the limbic and hypothalamic brain regions and alters central pro-opiomelanocortin (POMC) mRNA activity in adult rats. Adolescence is a critical developmental period of high vulnerability in which ethanol exposure alters corticotropin releasing factor, neuropeptide Y, substance P and neurokinin neuropeptide activities, all of which have key roles in ethanol consumption. Given the involvement of MC and the endogenous inverse agonist AgRP in ethanol drinking, here we evaluate whether a binge-like pattern of ethanol treatment during adolescence has a relevant impact on basal and/or ethanol-stimulated α-MSH and AgRP activities during adulthood. To this end, adolescent Sprague-Dawley rats (beginning at PND25) were pre-treated with either saline (SP group) or binge-like ethanol exposure (BEP group; 3.0 g/kg given in intraperitoneal (i.p.) injections) of one injection per day over two consecutive days, followed by 2 days without injections, repeated for a total of 8 injections. Following 25 ethanol-free days, we evaluated α-MSH and AgRP immunoreactivity (IR) in the limbic and hypothalamic nuclei of adult rats (PND63) in response to ethanol (1.5 or 3.0 g/kgi.p.) and saline. We found that binge-like ethanol exposure during adolescence significantly reduced basal α-MSH IR in the central nucleus of the amygdala (CeA), the arcuate nucleus (Arc) and the paraventricular nucleus of the hypothalamus (PVN) during adulthood. Additionally, acute ethanol elicited AgRP IR in the Arc. Rats given the adolescent ethanol treatment required higher doses of ethanol than saline-treated rats to express AgRP. In light of previous evidence that endogenous MC and AgRP regulate ethanol intake through MC-receptor signaling, we speculate that the α-MSH and AgRP disturbances induced by binge-like ethanol exposure during adolescence may contribute to excessive ethanol consumption during adulthood.

Alcohol intoxications during adolescence increase motivation for alcohol in adult rats and induce neuroadaptations in the nucleus accumbens

Adolescent alcohol binge drinking constitutes a major vulnerability factor to develop alcoholism. However, mechanisms underlying this susceptibility remain unknown. We evaluated the effect of adolescent binge-like ethanol intoxication on vulnerability to alcohol abuse in Sprague-Dawley rats. To model binge-like ethanol intoxication, every 2 days, rats received an ethanol injection (3.0 g/kg) for 2 consecutive days across 14 days either from postnatal day 30 (PND30) to 43 (early adolescence) or from PND 45 to PND 58 (late adolescence). In young adult animals, we measured free ethanol consumption in the two-bottle choice paradigm, motivation for ethanol in the operant self-administration task and both ethanol's rewarding and aversive properties in the conditioned place preference (CPP) and taste aversion (CTA) paradigms. While intermittent ethanol intoxications (IEI) during late adolescence had no effect on free-choice 10% ethanol consumption, we found that IEI during early adolescence promoted free-choice 10% ethanol consumption, enhanced motivation for ethanol in the self-administration paradigm and induced a loss of both ethanol-induced CPP and CTA in young adults. No modification in either sucrose self-administration or amphetamine-induced CPP was observed. As the nucleus accumbens (Nac) is particularly involved in addictive behavior, we analyzed IEI-induced long-term neuroadaptations in the Nac using c-Fos immunohistochemistry and an array of neurotransmission-related genes. This vulnerability to ethanol abuse was associated with a lower c-Fos immunoreactivity in the Nac and enduring alterations of the expression of Penk and Slc6a4, 2 neurotransmission-related genes that have been shown to play critical roles in the behavioral effects of ethanol and alcoholism.

Long-term consequences of developmental alcohol exposure on brain structure and function: therapeutic benefits of physical activity

Developmental alcohol exposure both early in life and during adolescence can have a devastating impact on normal brain structure and functioning, leading to behavioral and cognitive impairments that persist throughout the lifespan. This review discusses human work as well as animal models used to investigate the effect of alcohol exposure at various time points during development, as well as specific behavioral and neuroanatomical deficits caused by alcohol exposure. Further, cellular and molecular mediators contributing to these alcohol-induced changes are examined, such as neurotrophic factors and apoptotic markers. Next, this review seeks to support the use of aerobic exercise as a potential therapeutic intervention for alcohol-related impairments. To date, few interventions, behavioral or pharmacological, have been proven effective in mitigating some alcohol-related deficits. Exercise is a simple therapy that can be used across species and also across socioeconomic status. It has a profoundly positive influence on many measures of learning and neuroplasticity; in particular, those measures damaged by alcohol exposure. This review discusses current evidence that exercise may mitigate damage caused by developmental alcohol exposure and is a promising therapeutic target for future research and intervention strategies.

Increased anxiety-related behavior in male and female adult rats following early and late adolescent exposure to 3,4-methylenedioxymethamphetamine (MDMA)

Subsequent behavioral effects in adulthood of daily exposure to MDMA during early or late adolescence were assessed in both male and female rats. From either postnatal day (PND) 35 (early adolescence) or PND45 (late adolescence), PVG/c rats of each sex were exposed via intraperitoneal injections to saline or 10mg/kg MDMA for 10 consecutive days. They were regularly weighed during treatment and again on PND90. At this age, their anxiety-related behavior was determined from frequencies of ambulation, rearing, grooming, defecation and occupancy of the center and corners of an open field, as well as entries into and time spent in the light compartment of a light-dark box. Spatial and working memories were assessed by preferences for a novel Y-maze arm, and by recognition of a novel object. MDMA-exposed rats gained less weight during treatment than saline controls but were heavier on PND90 depending on their sex or age when treated. As shown by decreased open-field ambulation (for males only) and increased defecation plus fewer entries into the light compartment of the light-dark box and entries into both arms of a Y maze, MDMA exposure increased adult anxiety-related behavior particularly for rats treated during late adolescence. There was no evidence of any effects on either spatial or working memory.

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.

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.

Changes in histone acetylation in the prefrontal cortex of ethanol-exposed adolescent rats are associated with ethanol-induced place conditioning

Alcohol drinking during adolescence can induce long-lasting effects on the motivation to consume alcohol. Abnormal plasticity in reward-related processes might contribute to the vulnerability of adolescents to drug addiction. We have shown that binge-like ethanol treatment in adolescent rats induces alterations in the dopaminergic system and causes histone modifications in brain reward regions. Considering that histone acetylation regulates transcriptional activity and contributes to drug-induced alterations in gene expression and behavior, we addressed the hypothesis that ethanol is capable of inducing transcriptional changes by histone modifications in specific gene promoters in adolescent brain reward regions, and whether these events are associated with acquisition of place conditioning. After treating juvenile and adult rats with intermittent ethanol administration, we found that ethanol treatment upregulates histone acetyl transferase (HAT) activity in adolescent prefrontal cortex and increases histone (H3 or H4) acetylation and H3(K4) dimethylation in the promoter region of cFos, Cdk5 and FosB. Inhibition of histone deacetylase by sodium butyrate before ethanol injection enhances both up-regulation of HAT activity and histone acetylation of cFos, Cdk5 and FosB. Furthermore, co-administration of sodium butyrate with ethanol prolongs the extinction of conditioned place aversion and increased the reinstatement effects of ethanol in ethanol-treated adolescents, but not in ethanol-treated adult rats. These results indicate that ethanol exposure during adolescence induces chromatin remodeling, changes histone acetylation and methylation, and modify the effects of ethanol on place conditioning. They also suggest that epigenetic mechanisms might open up avenues to new treatments for binge drinking-induced drug addiction during adolescence.