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

Deleterious and protective effects of epothilone-D alone and in the context of amyloid β- and tau-induced alterations

Amyloid-β (Aβ) and hyperphosphorylated tau (P-tau) are Alzheimer's disease (AD) biomarkers that interact in a complex manner to induce most of the cognitive and brain alterations observed in this disease. Since the neuronal cytoskeleton is a common downstream pathological target of tau and Aβ, which mostly lead to augmented microtubule instability, the administration of microtubule stabilizing agents (MSAs) can protect against their pathological actions. However, the effectiveness of MSAs is still uncertain due to their state-dependent negative effects; thus, evaluating their specific actions in different pathological or physiological conditions is required. We evaluated whether epothilone-D (Epo-D), a clinically used MSA, rescues from the functional and behavioral alterations produced by intracerebroventricular injection of Aβ, the presence of P-tau, or their combination in rTg4510 mice. We also explored the side effects of Epo-D. To do so, we evaluated hippocampal-dependent spatial memory with the Hebb-Williams maze, hippocampal CA1 integrity and the intrinsic and synaptic properties of CA1 pyramidal neurons with the patch-clamp technique. Aβ and P-tau mildly impaired memory retrieval, but produced contrasting effects on intrinsic excitability. When Aβ and P-tau were combined, the alterations in excitability and spatial reversal learning (i.e., cognitive flexibility) were exacerbated. Interestingly, Epo-D prevented most of the impairments induced Aβ and P-tau alone and combined. However, Epo-D also exhibited some side effects depending on the prevailing pathological or physiological condition, which should be considered in future preclinical and translational studies. Although we did not perform extensive histopathological evaluations or measured microtubule stability, our findings show that MSAs can rescue the consequences of AD-like conditions but otherwise be harmful if administered at a prodromal stage of the disease.

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.

Use and abuse of dissociative and psychedelic drugs in adolescence

Adolescence is a period of profound developmental changes, which run the gamut from behavioral and neural to physiological and hormonal. It is also a time at which there is an increased propensity to engage in risk-taking and impulsive behaviors like drug use. This review examines the human and preclinical literature on adolescent drug use and its consequences, with a focus on dissociatives (PCP, ketamine, DXM), classic psychedelics (LSD, psilocybin), and MDMA. It is the case for all the substances reviewed here that very little is known about their effects in adolescent populations. An emerging aspect of the literature is that dissociatives and MDMA produce mixed reinforcing and aversive effects and that the balance between reinforcement and aversion may differ between adolescents and adults, with consequences for drug use and addiction. However, many studies have failed to directly compare adults and adolescents, which precludes definitive conclusions about these consequences. Other important areas that are largely unexplored are sex differences during adolescence and the long-term consequences of adolescent use of these substances. We provide suggestions for future work to address the gaps we identified in the literature. Given the widespread use of these drugs among adolescent users, and the potential for therapeutic use, this work will be crucial to understanding abuse potential and consequences of use in this developmental stage.

Adolescent binge-ethanol accelerates cognitive impairment and β-amyloid production and dysregulates endocannabinoid signaling in the hippocampus of APP/PSE mice

Previous research in rodents suggests that the long-term neurobehavioral disturbances induced by chronic ethanol (EtOH) exposure could be due to endocannabinoid system (ECS) alterations. Moreover, ECS failure has been proposed to mediate the cognitive impairment and β-amyloid production in Alzheimer disease (AD). Thus, in the present study, we evaluated the effects of adolescent EtOH binge drinking on the cognitive disturbances, hippocampal β-amyloid levels, and in the ECS expression on a transgenic mouse model (APP/PSEN, AZ) of AD. We exposed AZ and wild-type mice to a binge-drinking treatment during adolescence. At 6 and 12 months of age, we evaluated hippocampal-dependent learning and memory: β-amyloid concentrations and RNA and protein levels of cannabinoid type-2 receptors (CB2), diacylglycerol lipase-α (DAGLα), and monoacylglycerol lipase (MAGL) in the hippocampus. The results showed that binge-EtOH treatment worsens cognitive function and increases β-amyloid levels in AZ. At 6 months, EtOH heightens CB2 (RNA and protein) and DAGLα (RNA) expression in wild type but not in AZ. On the contrary, EtOH enhances MAGL RNA expression only in AZ. At 12 months, AZ displays increased levels of CB2 (RNA and protein) and DAGLα (protein) compared with control. Similar to what happens at 6 months, EtOH induces an increase in CB2 gene expression in wild type but not in AZ; however, it augments CB2 and DAGLα protein levels in both genotypes. Therefore, we propose that adolescent binge drinking accelerates cognitive deficits associated with aging and AD. It also accelerates hippocampal β-amyloid accumulation in AZ and affects differently the ECS response in wild type and AZ.

Role of mTOR-regulated autophagy in spine pruning defects and memory impairments induced by binge-like ethanol treatment in adolescent mice

Adolescence is a brain maturation developmental period during which remodeling and changes in synaptic plasticity and neural connectivity take place in some brain regions. Different mechanism participates in adolescent brain maturation, including autophagy that plays a role in synaptic development and plasticity. Alcohol is a neurotoxic compound and its abuse in adolescence induces neuroinflammation, synaptic and myelin alterations, neural damage and behavioral impairments. Changes in synaptic plasticity and its regulation by mTOR have also been suggested to play a role in the behavioral dysfunction of binge ethanol drinking in adolescence. Therefore, by considering the critical role of mTOR in both autophagy and synaptic plasticity in the developing brain, the present study aims to evaluate whether binge ethanol treatment in adolescence would induce dysfunctions in synaptic plasticity and cognitive functions and if mTOR inhibition with rapamycin is capable of restoring both effects. Using C57BL/6 adolescent female and male mice (PND30) treated with ethanol (3 g/kg) on two consecutive days at 48-hour intervals over 2 weeks, we show that binge ethanol treatment alters the density and morphology of dendritic spines, effects that are associated with learning and memory impairments and changes in the levels of both transcription factor CREB phosphorylation and miRNAs. Rapamycin administration (3 mg/kg) prior to ethanol administration restores ethanol-induced changes in both plasticity and behavior dysfunctions in adolescent mice. These results support the critical role of mTOR/autophagy dysfunctions in the dendritic spines alterations and cognitive alterations induced by binge alcohol in adolescence.

Oral Monosodium Glutamate Administration Causes Early Onset of Alzheimer's Disease-Like Pathophysiology in APP/PS1 Mice

Glutamate excitotoxicity has long been related to Alzheimer's disease (AD) pathophysiology, and it has been shown to affect the major AD-related hallmarks, amyloid-β peptide (Aβ) accumulation and tau phosphorylation (p-tau). We investigated whether oral administration of monosodium glutamate (MSG) has effects in a murine model of AD, the double transgenic mice APP/PS1. We found that AD pathogenic factors appear earlier in APP/PS1 when supplemented with MSG, while wildtype mice were essentially not affected. Aβ and p-tau levels were increased in the hippocampus in young APP/PS1 animals upon MSG administration. This was correlated with increased Cdk5-p25 levels. Furthermore, in these mice, we observed a decrease in the AMPA receptor subunit GluA1 and they had impaired long-term potentiation. The Hebb-Williams Maze revealed that they had memory deficits. We show here for the first time that oral MSG supplementation can accelerate AD-like pathophysiology in a mouse model of AD.

Neuronal and peripheral damages induced by synthetic psychoactive substances: an update of recent findings from human and animal studies

Preclinical and clinical studies indicate that synthetic psychoactive substances, in addition to having abuse potential, may elicit toxic effects of varying severity at the peripheral and central levels. Nowadays, toxicity induced by synthetic psychoactive substances poses a serious harm for health, since recreational use of these substances is on the rise among young and adult people. The present review summarizes recent findings on the peripheral and central toxicity elicited by “old” and “new” synthetic psychoactive substances in humans and experimental animals, focusing on amphetamine derivatives, hallucinogen and dissociative drugs and synthetic cannabinoids.

The intermittent administration of ethanol during the juvenile period produces changes in the expression of hippocampal genes and proteins and deterioration of spatial memory

BACKGROUND

Binge drinking is a pattern of alcohol intake characterized by excessive and intermittent alcohol consumption over a very short period of time that is more used during adolescence. We aim to compare the lasting effects of a chronic-moderate vs. this intermittent-excessive way of alcohol intake during adolescence in spatial memory and in the expression of glutamatergic receptors and GSK3β activity.

METHODS

Adolescent male Wistar rats were given ethanol/saline i.p. injections in four different groups: High-I (4 g/kg of a 25% (vol/vol) every 3 days), Low-I (1 g/kg of a 5% (vol/vol) every 3 days), M (0.3 g/kg of a 2.5% (vol/vol) daily) and Control (C, sterile isotonic saline daily). Rats received ethanol for up to five 3-day cycles. Spatial memory was measured by spontaneous alternation in the Y-Maze. Gene and protein expression of hippocampal proteins were also analysed.

RESULTS

Both high- and low-intermittent ethanol administration produced spatial memory impairment and changes in glutamatergic receptors gene expression were observed regardless of the pattern of exposure. High doses of intermittent alcohol administration produced an increase of phosphorylation of GSK3β Ser9. Moreover, moderate alcohol administration produced a down-regulation of the AMPAR 2/3 ratio despite lack of spatial memory deficits.

CONCLUSIONS

Excessive and intermittent ethanol exposure during adolescence impaired the spatial memory processes during adulthood regardless of the amount of alcohol administered. Moreover, chronic-moderate and intermittent pattern induced changes in the expression of glutamatergic receptors. In addition, high-intermittent ethanol exposure during adolescence inactivated GSK3β by increasing its phosphorylation in Ser9.

Behavioral profile of intermittent vs continuous access to a high fat diet during adolescence

Over the past few years, the effects of a high-fat diet (HFD) on cognitive functions have been broadly studied as a model of obesity, although no studies have evaluated whether these effects are maintained after the cessation of this diet. In addition, the behavioral effects of having a limited access to an HFD (binge-eating pattern) are mostly unknown, although they dramatically increase the vulnerability to drug use in contrast to having continuous access. Thus, the aim of the present study was to compare the effects of an intermittent versus a continuous exposure to an HFD during adolescence on cognition and anxiety-like behaviors, as well as to study the changes observed after the interruption of this diet. Adolescent male mice received for 40 days a standard diet, an HFD with continuous access or an HFD with sporadic limited access (2 h, three days a week). Two additional groups were fed with intermittent or continuous access to the HFD and withdrawn from this diet 15 days before the behavioral tests. Only the animals with a continuous access to the HFD showed higher circulating leptin levels, increased bodyweight, marked memory and spatial learning deficits, symptoms that disappeared after 15 days of HFD abstinence. Mice that binged on fat only showed hyperlocomotion, which normalized after 15 days of HFD cessation. However, discontinuation of fat, either in a binge or a continuous pattern, led to an increase in anxiety-like behavior. These results highlight that exposure to a high-fat diet during adolescence induces alterations in brain functions, although the way in which this diet is ingested determines the extent of these behavioral changes.

Green tea polyphenols ameliorate ethanol-induced spatial learning and memory impairments by enhancing hippocampus NMDAR1 expression and CREB activity in rats

The current research probed into the effects of green tea polyphenols (GTPs) on ethanol-induced spatial learning and memory impairments and inquired the potential molecular mechanism in rats. Thirty 8-week-old male Sprague-Dawley rats were randomly divided into three groups. The control group (control, n=10), ethanol group (ethanol, n=10), and GTPs intervention group (GTP, n=10) received gavage administration of saline, ethanol, and ethanol-GTP solution, respectively, for 8 weeks. Morris water maze was applied to assess the spatial learning and memory function of rats in each group at the last week of treatment. There was no dramatic change in body weight of rats in the different groups. Compared with rats in the control group, 8-week ethanol gavaged rats showed increased escape latency period and decreased time in the target quadrant. Moreover, 8-week ethanol gavage decreased the density of pyramidal layer neurons, expression of NMDAR1, and CREB phosphorylation in the hippocampus region. In contrast, GTP intervention decreased escape latency period and increased the time in the target quadrant, the density of pyramidal layer neurons, expression of NMDAR1, and CREB phosphorylation in the hippocampus region. The current findings indicated that GTP intervention can improve ethanol-induced spatial learning and memory impairments in rats after ethanol withdrawal, which is related to the upregulated density of pyramidal layer neurons, expression of NMDAR1, and CREB phosphorylation in the hippocampus region.

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.

Long-term effects of repeated social stress on the conditioned place preference induced by MDMA in mice

Previous studies have demonstrated that social defeat stress increases the rewarding effects of psychostimulant drugs such as cocaine and amphetamine. In the present study we evaluated the long-term effects of repeated social defeat (RSD) on the rewarding effects of ±3,4-methylenedioxymethamphetamine (MDMA) hydrochloride in the conditioned place preference (CPP) paradigm. Adolescent and young adult mice were exposed to four episodes of social defeat (on PND 29-40 and PND 47-56, respectively) and were conditioned three weeks later with 1.25 or 10mg/kg i.p. of MDMA (experiment 1). The long-term effects of RSD on anxiety, social behavior and cognitive processes were also evaluated in adult mice (experiment 2). RSD during adolescence enhanced vulnerability to priming-induced reinstatement in animals conditioned with 1.25mg/kg of MDMA and increased the duration of the CPP induced by the 10mg/kg of MDMA. The latter effect was also observed after RSD in young adult mice, as well as an increase in anxiety-like behavior, an alteration in social interaction (reduction in attack and increase in avoidance/flee and defensive/submissive behaviors) and an impairment of maze learning. These results support the idea that RSD stress increases the rewarding effects of MDMA and induces long-term alterations in anxiety, learning and social behavior in adult mice. Thus, exposure to stress may increase the vulnerability of individuals to developing MDMA dependence, which is a factor to be taken into account in relation to the prevention and treatment of this disorder.

Neuroimmune activation and myelin changes in adolescent rats exposed to high-dose alcohol and associated cognitive dysfunction: a review with reference to human adolescent drinking

AIMS

The aim of the study was to assess whether intermittent ethanol administration to adolescent rats activates innate immune response and TLRs signalling causing myelin disruption and long-term cognitive and behavioural deficits.

METHODS

We used a rat model of intermittent binge-like ethanol exposure during adolescence.

RESULTS

Binge-like ethanol administration to adolescent rats increased the gene expression of TLR4 and TLR2 in the prefrontal cortex (PFC), as well as inflammatory cytokines TNFα and IL-1β. Up-regulation of TLRs and inflammatory mediators were linked with alterations in the levels of several myelin proteins in the PFC of adolescent rats. These events were associated with previously reported long-term cognitive dysfunctions. Conversely, the same ethanol treatment did not cause significant changes in either inflammatory mediators or myelin changes in the brain of adult rats.

CONCLUSION

Activation of innate immune receptors TLRs in the PFC appears to be involved in the neuroinflammation and demyelination processes induced by ethanol exposure during adolescence. The findings support the vulnerability of the juvenile brain to the effects of ethanol and the long-term cognitive consequences of binge drinking. In addition, ethanol-induced PFC dysfunctions might underlie the propensity of adolescents for impulsivity and to ignore the negative consequences of their behaviour, both of which could increase the risk of substance abuse.