Environmental enrichment reverses increased addiction risk caused by prenatal ethanol exposure

A bibliometric analysis of studies on environmental enrichment spanning 1967-2024: patterns and trends over the years

Environmental Enrichment (EE) has received considerable attention for its potential to enhance cognitive and neurobiological outcomes in animal models. This bibliometric analysis offers a comprehensive evaluation of the EE research spanning from 1967 to 2024, utilizing data extracted from Scopus and analyzed through R and VOSviewer. The volume of publications, citation patterns, and collaborations were systematically reviewed, highlighting important contributions and emerging trends within the field of animal research. Core concepts of EE research are mapped, revealing key themes such as neuroplasticity, cognitive function, and behavioral outcomes. A significant increase in EE research is demonstrated, particularly after the year 2000, reflecting growing scientific and public interest in EE paradigms. This analysis provides insights into the global contributions and collaborative networks that have shaped EE studies over time. The role of EE in advancing the understanding of neurobiological, neurodevelopmental, and neurodegenerative processes is underscored. Influential contributors, leading countries, and high-impact journals in the field of EE are identified, offering a valuable resource for researchers seeking to understand or extend the current knowledge base. The strategic selection of keywords and rigorous data curation methods ensure that the findings accurately reflect the most impactful aspects of EE research in animals. This study serves as an essential reference for future explorations and applications of EE across disciplines. By providing a clear and structured overview of the field, this paper aims to serve as a foundation for ongoing and future research initiatives, encouraging more robust investigations and applications of EE to enhance cognitive and neurological health globally.

New therapeutics for the prevention or amelioration of fetal alcohol spectrum disorders: a narrative review of the preclinical literature

Background: Ethanol consumption during pregnancy induces enduring detrimental effects in the offspring, manifesting as a spectrum of symptoms collectively termed as Fetal Alcohol Spectrum Disorders (FASD). Presently, there is a scarcity of treatments for FASD.Objectives: To analyze current literature, emphasizing evidence derived from preclinical models, that could potentially inform therapeutic interventions for FASD.Methods: A narrative review was conducted focusing on four prospective treatments: nutritional supplements, antioxidants, anti-inflammatory compounds and environmental enrichment. The review also highlights innovative therapeutic strategies applied during early (e.g. folate administration, postnatal days 4-9) or late (e.g. NOX2 inhibitors given after weaning) postnatal stages that resulted in significant improvements in behavioral responses during adolescence (a critical period marked by the emergence of mental health issues in humans).Results: Our findings underscore the value of treatments centered around nutritional supplementation or environmental enrichment, aimed at mitigating oxidative stress and inflammation, implying shared mechanisms in FASD pathogenesis. Moreover, the review spotlights emerging evidence pertaining to the involvement of novel molecular components with potential pharmacological targets (such as NOX2, MCP1/CCR2, PPARJ, and PDE1).Conclusions: Preclinical studies have identified oxidative imbalance and neuroinflammation as relevant pathological mechanisms induced by prenatal ethanol exposure. The relevance of these mechanisms, which exhibit positive feedback loop mechanisms, appear to peak during early development and decreases in adulthood. These findings provide a framework for the future development of therapeutic avenues in the development of specific clinical treatments for FASD.

Environmental enrichment and complementary clinical interventions as therapeutic approaches for alcohol use disorder in animal models and humans

Alcohol use disorder (AUD) is a multifactorial disorder arising from a complex interplay of various genetic, environmental, psychological, and social factors. Environmental factors influence alcohol misuse and can lead to AUD. While stress plays a crucial role in the onset and progression of this disorder, environmental enrichment (EE) also influences ethanol-induced behavioral and neurobiological responses. These alterations include reduced ethanol consumption, diminished operant self-administration, attenuated behavioral sensitization, and enhanced conditioned place preference. EE exerts modulatory effects on multiple neurobiological processes, such as the brain-derived neurotrophic factor/TrkB signaling pathway, the oxytocinergic system, and the hypothalamic-pituitary-adrenal axis. EE, which includes stimulating activities to counteract ethanol effects in animal studies, has parallels in human intervention that have shown potential benefits. Physical activity, cognitive behavioral therapy, and meditation, alongside techniques involving cognitive stimulation, social interaction, and recreational activities, may lead to more effective therapeutic outcomes in treatments of AUD.

The Fetal Alcohol Spectrum Disorders-An Overview of Experimental Models, Therapeutic Strategies, and Future Research Directions

Since the establishment of a clear link between maternal alcohol consumption during pregnancy and certain birth defects, the research into the treatment of FASD has become increasingly sophisticated. The field has begun to explore the possibility of intervening at different levels, and animal studies have provided valuable insights into the pathophysiology of the disease, forming the basis for implementing potential therapies with increasingly precise mechanisms. The recent reports suggest that compounds that reduce the severity of neurodevelopmental deficits, including glial cell function and myelination, and/or target oxidative stress and inflammation may be effective in treating FASD. Our goal in writing this article was to analyze and synthesize current experimental therapeutic interventions for FASD, elucidating their potential mechanisms of action, translational relevance, and implications for clinical application. This review exclusively focuses on animal models and the interventions used in these models to outline the current direction of research. We conclude that given the complexity of the underlying mechanisms, a multifactorial approach combining nutritional supplementation, pharmacotherapy, and behavioral techniques tailored to the stage and severity of the disease may be a promising avenue for further research in humans.

Prenatal ethanol exposure leads to persistent anxiety-like behavior during adulthood indicated by reduced horizontal and vertical exploratory behaviors

Background

Fetal alcohol spectrum disorders (FASD) caused by prenatal ethanol exposure (PE) consist of many cognitive/behavioral deficits. Studies have reported that PE leads to impairments of learning and memory, attention, executive function, and anxiety. Open field (OF) is a common behavioral model which offers comprehensive ethological information. Here, we analyzed multiple parameters of OF to examine anxiety behavior and habituation after PE.

Material and Methods

Pregnant Sprague Dawley rats were gavaged twice/day with 0 or 3 g/kg/treatment ethanol (15% w/v) during gestational day (GD) 8-20, mimicking second-trimester heavy PE in humans. The control and PE adult offspring were subjected to OF task in different ambient light levels with or without acute stress.

Results

Prenatal ethanol exposure did not influence the overall locomotor activities or habituation in the OF. In lower ambient light, no PE effects could be detected. In higher ambient light, female PE rats showed less activities in the center zone, indicative of increased anxiety. Males show lower activities in the center zone only after acute stress. Rats spent <2% of the time in the center zone compared to >75% of the time in the corner zone where they engaged in frequent rearing activities (vertical exploration; exploratory rearing). Prenatal ethanol exposure led to lower rearing activities in the corner in both males and females. Acute stress masks the PE effects in males but not in females.

Discussion

The results support that heavy PE leads to persistent anxiety-like behavior during adulthood in both sexes. This conclusion is supported by using multiple parameters of exploratory behavior in the OF, including the rearing activities in the corner to reach reliable quantification of anxiety-like behavior.

Prenatal ethanol exposure causes anxiety-like phenotype and alters synaptic nitric oxide and endocannabinoid signaling in dorsal raphe nucleus of adult male rats

Mood disorders, including anxiety and depression caused by prenatal ethanol exposure (PE) are prevalent conditions in fetal alcohol spectrum disorders (FASDs). Prenatal ethanol exposure is associated with persistent dysfunctions of several neurotransmitter systems, including the serotonin (5-HT) system, which plays a major role in mood regulation and stress homeostasis. While PE is known to disrupt the development of the 5-HT system, the cellular mechanisms by which it alters the function of dorsal raphe nucleus (DRn) 5-HT neurons and their synaptic inputs remain unknown. Here, we used a second-trimester binge-drinking pattern PE (two daily gavages of 15% w/v ethanol at 3 g/kg, 5-6 h apart) during gestational days 8 - 20 and measured anxiety-like behaviors of adult male rats using the elevated plus (EPM) and zero (ZM) mazes. We also employed ex-vivo electrophysiological and pharmacological approaches to unravel the mechanisms by which PE alters the excitability and synaptic transmission onto DRn 5-HT neurons. We found that PE enhanced anxiety-like behaviors in adult male rats and induced a persistent activation of DRn 5-HT neurons. The PE-induced activation of DRn 5-HT neurons was largely mediated by potentiation of DRn glutamate synapses, which was caused by activation of the nitrergic system and impaired endocannabinoid signaling. As such, the present study reveals "push-pull" effects of PE on nitrergic and eCB signaling, respectively, which mediate the enhanced activity of DRn 5-HT neurons and could contribute to anxiety-like behaviors observed in animal model of FASD.

Bored at home?—A systematic review on the effect of environmental enrichment on the welfare of laboratory rats and mice

Boredom is an emotional state that occurs when an individual has nothing to do, is not interested in the surrounding, and feels dreary and in a monotony. While this condition is usually defined for humans, it may very well describe the lives of many laboratory animals housed in small, barren cages. To make the cages less monotonous, environmental enrichment is often proposed. Although housing in a stimulating environment is still used predominantly as a luxury good and for treatment in preclinical research, enrichment is increasingly recognized to improve animal welfare. To gain insight into how stimulating environments influence the welfare of laboratory rodents, we conducted a systematic review of studies that analyzed the effect of enriched environment on behavioral parameters of animal well–being. Remarkably, a considerable number of these parameters can be associated with symptoms of boredom. Our findings show that a stimulating living environment is essential for the development of natural behavior and animal welfare of laboratory rats and mice alike, regardless of age and sex. Conversely, confinement and under-stimulation has potentially detrimental effects on the mental and physical health of laboratory rodents. We show that boredom in experimental animals is measurable and does not have to be accepted as inevitable.

Prenatal ethanol exposure impairs sensory processing and habituation to visual stimuli, effects normalized by enrichment of postnatal environmental

BACKGROUND

Individuals with fetal alcohol spectrum disorders (FASD) often show processing deficits in all sensory modalities. Using an operant light reinforcement model, we tested whether prenatal ethanol exposure (PE) alters operant responding to elicit a contingent sensory stimulus-light onset (turning on the light) and habituation to this behavior in rats. We also explored whether postnatal environmental enrichment could ameliorate PE-induced deficits.

METHODS

Pregnant Sprague Dawley rats were gavaged twice/day with 0 or 3 g/kg/treatment ethanol (15% w/v) during gestational days 8-20, mimicking second-trimester heavy PE in humans. The offspring were reared in a standard housing condition or an enriched condition. Adult male and female offspring underwent an operant light reinforcement experiment with either a short-access or a long-access procedure. A dishabituation test was also conducted to characterize the habituation process.

RESULTS

In the short-access procedure, PE led to increased operant responding to the contingent light onset in both sexes reared in the standard housing condition. Such an effect was not observed in rats reared in enriched conditions due to an overall decrease in responding. Moreover, rats reared in enriched conditions showed greater short-term habituation. In the long access procedure, PE rats showed increased responding and impaired long-term habituation. The long-access procedure facilitated both short-term and long-term habituation in control and PE rats.

CONCLUSION

Prenatal ethanol exposure increases responding to contingent light onset and impairs the long-term habituation process. The PE-induced deficits were ameliorated by rearing in the enriched environment and increasing the duration and frequency of exposure to light onset. The PE-induced effects are like increased sensation-seeking, a subtype of sensory-processing deficit that is often observed in individuals with FASD. Our findings could inform a suitable animal model for investigating the underlying mechanisms and possible intervention strategies for sensory deficits in FASD.

Enriched environment and social isolation differentially modulate addiction-related behaviors in male offspring of morphine-addicted dams: The possible role of μ-opioid receptors and ΔFosB in the brain reward pathway

Prenatal opioids exposure negatively affects the neurobehavioral abilities of children born from dependence dams. Adolescent housing conditions can buffer the detrimental impacts of early life experiences or contradictory can worsen individual psychosocial functions. The present study investigated the effects of maternal morphine dependence and different rearing conditions on behaviors and protein expression in brain reward circuits of male pups. Female Wistar rats a week before conception, during pregnancy and lactation were injected twice daily with escalating doses of morphine or saline. On a postnatal day 21, male pups were weaned and subjected to three different environments for two months: standard (STD), isolated (ISO), or enriched environment (EE). The anxiety and drug-related reward were measured using elevated plus maze, open field test, and conditioned place preference. Western blotting was used to determine the protein level of ΔFosB and μ-opioid receptor proteins in the striatum and the midbrain of male offspring, respectively. Results showed that maternal morphine administration dramatically increased anxiety-like and morphine place preference behaviors in offspring. Also, ISO condition aggravated these behavioral outcomes. While, rearing in EE could attenuate anxiety and morphine conditioning in pups. At molecular levels, maternal morphine exposure and social isolation markedly increased both of ΔFosB and μ-opioid receptor proteins expression. However, rearing in the EE declined ΔFosB protein expression. Together, these findings help to elucidate long lasting impacts of early life morphine exposure and rearing environment on the behavioral and molecular profile of addicted individuals.

Moderate prenatal ethanol exposure leads to attention deficits in both male and female rats

BACKGROUND

Attention deficits caused by prenatal ethanol (EtOH) exposure (PE) are a prevalent condition in fetal alcohol spectrum disorders (FASDs). Importantly, the deficits are observed in individuals with FASD who have normal IQs and show no dysmorphic facial features caused by heavy PE. These observations suggest that even moderate PE could lead to attention deficits. This possibility was investigated in the present study using a rat model.

METHODS

Pregnant Sprague Dawley rats were administered EtOH (3 g/kg/day) or vehicle via intragastric gavage on gestational days 8 to 20. The blood EtOH concentration (BEC) in EtOH-treated rats was 87.7 ± 1.2 mg/dl (1 h after the gavage), similar to the BECs reported in other moderate PE studies in rodents. Moderate PE did not produce teratogenic effects on birthweight or litter size. The adult offspring underwent a 2-choice reaction time task.

RESULTS

Moderate PE led to augmented action impulsivity in both sexes, indicated by more rapid response initiation and more premature responses. Deficits were more marked in males than in females. No greater lapses of attention, assessed by incorrect or relatively slow responses, were observed in rats of either sex with moderate PE. In addition, no deficits in learning or motor function were detected after moderate PE. Interestingly, rats with moderate PE completed more trials than controls.

CONCLUSIONS

Our results confirm that moderate PE leads to attention deficits in both sexes, which is demonstrated by greater action impulsivity, but not more lapses of attention. This effect differs from that of heavy PE, as shown in our previous study, which is manifested as impaired action impulsivity and lapses of attention in both sexes.

Maternal Morphine Exposure and Post-Weaning Social Isolation Impair Memory and Ventral Striatum Dopamine System in Male Offspring: Is an Enriched Environment Beneficial?

Maternal opioids abuse has some deleterious consequences on next generations. Besides, children's rearing conditions can affect the behavioral states and brain plasticity in their later life. In the present study, we investigated the effects of maternal morphine (MOR) treatment and post-weaning rearing conditions on memory, pain threshold, and the ventral striatum dopaminergic activity in male offspring. Female Wistar rats were treated twice daily either with escalating doses of MOR or with normal saline (NS) one week before mating, during pregnancy and lactation. After weaning, the male pups were assigned to six groups and then raised for an 8-week period under three different conditions: standard (STD), isolated (ISO) or enriched environment (EE). The behavioral tests, including passive avoidance task, novel object recognition, and tail-flick test, were also performed. Moreover, the ventral striatum dopamine's content (DA), mRNA expressions of dopamine receptor 1(D1R) and dopamine receptor 2 (D2R), and dopamine transporter (DAT) were evaluated. The obtained data showed that maternal MOR exposure and post-weaning social isolation could dramatically impair memory in offspring, while EE could reverse these adverse outcomes. Moreover, results of tail flick latency indicated the increased pain threshold in EE animals. At molecular level, maternal MOR injections and social isolation reduced DA levels and altered expressions of D1R, D2R, and DAT within the ventral striatum of these male offspring. However, post-weaning EE partially buffered these changes. Our finding signified the effects of maternal MOR exposure and social isolation on the behaviors and neurochemistry of brain in next generation, and it also provided evidence on reversibility of these alterations following EE.

Alcohol use in pregnancy and its impact on the mother and child

AIMS

To review the impact of prenatal alcohol exposure on the outcomes of the mother and child.

DESIGN

Narrative review.

SETTING

Review of literature.

PARTICIPANTS

Mothers and infants affected by prenatal alcohol use.

MEASUREMENTS

Outcomes of mothers and children.

FINDINGS

Prenatal alcohol exposure is one of the most important causes of preventable cognitive impairment in the world. The developing neurological system is exquisitely sensitive to harm from alcohol and there is now also substantial evidence that alcohol-related harm can extend beyond the individual person, leading to epigenetic changes and intergenerational vulnerability and disadvantage. There is no known safe level or timing of drinking for pregnant or lactating women and binge drinking (> four drinks within 2 hours for women) is the most harmful. Alcohol-exposure increases the risk of congenital problems, including Fetal Alcohol Spectrum Disorder (FASD) and its most severe form, Fetal Alcohol Syndrome (FAS).

CONCLUSION

The impact of FASD and FAS is enduring and life-long with no current treatment or cure. Emerging therapeutic options may mitigate the worst impact of alcohol exposure but significant knowledge gaps remain. This review discusses the history, epidemiology and clinical presentations of prenatal alcohol exposure, focusing on FASD and FAS, and the impact of evidence on future research, practice and policy directions.

Environmental Enrichment During Adolescence Mitigates Cognitive Deficits and Alcohol Vulnerability due to Continuous and Intermittent Perinatal Alcohol Exposure in Adult Rats

Perinatal alcohol exposure affects ontogenic neurodevelopment, causing physical and functional long-term abnormalities with limited treatment options. This study investigated long-term consequences of continuous and intermittent maternal alcohol drinking on behavioral readouts of cognitive function and alcohol vulnerability in the offspring. The effects of environmental enrichment (EE) during adolescence were also evaluated. Female rats underwent continuous alcohol drinking (CAD)—or intermittent alcohol drinking paradigm (IAD), along pregestation, gestation, and lactation periods—equivalent to the whole gestational period in humans. Male offspring were reared in standard conditions or EE until adulthood and were then assessed for declarative memory in the novel object recognition test; spatial learning, cognitive flexibility, and reference memory in the Morris water maze (MWM); alcohol consumption and relapse by a two-bottle choice paradigm. Our data show that perinatal CAD decreased locomotor activity, exploratory behavior, and declarative memory with respect to controls, whereas perinatal IAD displayed impaired declarative memory and spatial learning and memory. Moreover, both perinatal alcohol-exposed offspring showed higher vulnerability to alcohol consummatory behavior than controls, albeit perinatal IAD rats showed a greater alcohol consumption and relapse behavior with respect to perinatal-CAD progeny. EE ameliorated declarative memory in perinatal CAD, while it mitigated spatial learning and reference memory impairment in perinatal-IAD progeny. In addition, EE decreased vulnerability to alcohol in both control and perinatal alcohol-exposed rats. Maternal alcohol consumption produces drinking pattern-related long-term consequences on cognition and vulnerability to alcohol in the offspring. However, increased positive environmental stimuli during adolescence may curtail the detrimental effects of developmental alcohol exposure.

Environmental enrichment and its influence on rodent offspring and maternal behaviours, a scoping style review of indices of depression and anxiety

Environmental enrichment is a widely used experimental manipulation that consistently shows measurable effects on rodent behaviour across the lifespan. This scoping review assesses and thematically summarizes the literature of the past decade concerning the effects of environmental enrichment applied during sensitive developmental periods in rodent mothers and offspring. Maternal behaviours as well as maternal and offspring anxiety- and depressive-like behaviours are considered. Relevant terms were searched across five databases (Embase, MEDLINE, PsycINFO, PubMed, Web of Science) and articles were screened with inclusion and exclusion criteria. The remaining articles were thematically analysed. Our results suggest that a greater number of articles reviewed the impacts of environmental enrichment on offspring anxiety-like behaviour (n = 23) rather than on depressive-like behaviour (n = 11) or maternal caregiving behaviour (n = 12). Maternal anxiety- (n = 4) or depressive-like (n = 2) behaviours are not often evaluated for in enrichment studies. The main behavioural tests of anxiety that were reviewed include the elevated plus-maze, the open field test, and the light-dark box whereas those for depression included the forced swim test and the sucrose preference test. Our results yielded mixed findings and significant variation in behavioural responses across all tests. In mothers, trends of increased maternal care behaviours and decreased maternal depressive-like behaviours in enriched mothers were appreciated. Enrichment during the gestational period was identified as pivotal to creating behavioural change in mother subjects. In enriched offspring rodents, a trend towards decreased anxiety-like behaviours was observed most often. Potential confounds inherent in enrichment paradigms and relevant theories of enrichment and their relation to rodent behavioural tests are discussed.

Environmental enrichment during adolescence heightens ethanol intake in female, but not male, adolescent rats that are selectively bred for high and low ethanol intake during adolescence

Background: Discriminating between adolescents who will eventually have ethanol use problems from those who do not is important. Environmental enrichment is a promising approach to reduce drug-related problems, but its impact on ethanol's effects and intake is being scrutinized. Objective: We tested the effects of environmental enrichment on ethanol intake, preference, and anxiety-like response as well as shelter seeking and risk-taking behaviors. Methods: Experiment 1 examined ethanol intake, preference, and anxiety-like responses in 46 male and 54 female Wistar rats that were derived from a short-term breeding program that selected for high and low ethanol drinking during adolescence (ADHI₂ and ADLO₂ lines, respectively). Shelter-seeking and risk-taking behaviors were assessed (Experiment 2) in ADHI₂ and ADLO₂ rats (73 males, 76 females) reared under environmental enrichment or standard housing conditions and given doses of ethanol (2.5 g/kg, intraperitoneal) for 3 weeks. Environmental enrichment was applied on postnatal days 21-42. Ethanol intake was measured on postnatal days 42-68. Anxiety-like behavior and exploratory responses were assessed using the light-dark box and multivariate concentric square field test. Results: In Experiment 1, environmental enrichment increased ethanol intake in female, but not male, ADHI₂ and ADLO₂ rats (p < 0.05). In the baseline measurement of Experiment 2, ADHI₂ rats exhibited reduced risk-taking and increased anxiety-like behavior (p < .05). After exposure to environmental enrichment the ADHI and ADLO rats, both males and females, exhibited increased risk-taking and exploratory behavior (p < 0.05). Conclusions: Environmental enrichment appears to increase ethanol intake in female rats by promoting the exploration of new environments or stimuli. The findings indicate that environmental enrichment increased ethanol intake in female, but not male, rats. Clinical programs that treat alcohol use disorder by emphasizing environmental stimulation should be designed with caution.

Environmental enrichment increases cue-dependent freezing and behavioral despair but decreases anxiety-like behavior in rats

While post-traumatic stress disorder (PTSD) can develop after exposure to severe traumatic events, data have shown that individuals with high sensation-seeking personality traits are less prone to developing PTSD. The current study used the rodent environmental enrichment preclinical model of sensation-seeking to determine if similar sensation seeking effects in animal models of PTSD-like behaviors were found. The study also attempted to determine whether environmental enrichment altered the effects of midazolam on these PTSD-like behaviors. Male Sprague-Dawley rats were received at postnatal day (PND) 21 and placed into either an enriched (EC), isolated (IC), or social (SC) condition. Beginning on PND 51, the animals underwent 3 fear conditioning trials where a tone was paired with a 2 s 0.7 mA footshock. Twenty-four hours later, rats were given 15-min i.p. pretreatments of 0, 0.5, or 1.5 mg/kg midazolam, before being placed into fear conditioning chambers for a test of expression of conditioned fear response in a novel context. Following fear conditioning, rodents were also tested in the elevated plus maze (EPM) and the forced swim task (FST) following pretreatments of midazolam. Results from fear conditioning indicated IC rats showed a significant decrease in freezing during acquisition compared to EC and SC rats. Also, during expression, IC rats had lower freezing following saline injections and 0.5 mg/kg midazolam but were equal in time freezing to EC and SC rats following 1.5 mg/kg midazolam. In the EPM there were no effects of midazolam and IC rats showed decreased time spent in the open arms compared to EC and SC rats. In FST, IC rats spent less time immobile and more time swimming compared to EC and SC rats. Overall, results suggest that the rodent environmental enrichment model of sensation-seeking seems to parallel the effects of sensation-seeking on likelihood of PTSD symptoms seen in humans.

Enriched Environment Decreases Cognitive Impairment in Elderly Rats With Prenatal Mobile Phone Exposure

Mobile phone use has rapidly increased worldwide, and pregnant women are passively or actively exposed to the associated electromagnetic radiation. Maternal cell phone exposure is related to behavioral difficulties in young offspring. However, whether prenatal mobile phone exposure can predispose the elderly offspring to cognitive impairment is unclear. The enriched environment (EE) has shown positive effects on cognition in an immature brain, but its impact on aging offspring after prenatal cell phone exposure is unknown. This study aimed to investigate whether prenatal exposure to mobile phone exerts long-term effects on cognition in elderly rat offspring and whether EE during adulthood can rescue cognitive impairment by altering the synaptic plasticity. Pregnant rats were subjected to prenatal short-term or long-term cell phone exposure and offspring rats were randomly assigned to standard or EE. Spatial learning and memory were investigated using Morris water maze (MWM) in elderly rat offspring. Hippocampal cellular morphology was assessed by hematoxylin-eosin staining and synaptic ultrastructure was evaluated with transmission electron microscopy. Expression of synaptophysin (SYN), postsynaptic density-95 (PSD-95), and brain-derived neurotrophic factor (BDNF) were detected by western blot. The results demonstrated that prenatal long-term but not short-term exposure to mobile phone lead to cognitive impairment, morphological changes in the hippocampal cells, reduced synaptic number, decreased SYN, PSD-95, and BDNF expression in elderly offspring, which were alleviated by postnatal EE housing. These findings suggest that prenatal long-term mobile phone exposure may pose life-long adverse effects on elderly offspring and impair cognition by disrupting the synaptic plasticity, which may be reversed by postnatal EE housing.

Prenatal Ethanol Exposure and Postnatal Environmental Intervention Alter Dopaminergic Neuron and Microglia Morphology in the Ventral Tegmental Area During Adulthood

BACKGROUND

Prenatal ethanol exposure (PE) impairs midbrain dopaminergic (DA) neuron function, which might contribute to various cognitive and behavioral deficits, including attention deficits and increased addiction risk, often observed in individuals with fetal alcohol spectrum disorders. Currently, the underlying mechanisms for PE-induced deficits are unclear. PE could lead to neuroinflammation by activating microglia, which play an important role in synaptic function. In the present study, we investigated PE effects on microglial activation and DA neuron density and morphology in the ventral tegmental area (VTA). Since postnatal environmental enrichment can reduce neuroinflammation and ameliorate several PE-induced behavioral deficits, we examined if a postnatal environmental intervention strategy using neonatal handling and postweaning complex housing could reverse PE effects on VTA DA neurons and microglia.

METHODS

Pregnant rats received 0 or 6 g/kg/d ethanol by 2 intragastric intubations on gestation days 8 to 20. After birth, rats were reared in the standard laboratory or enriched condition. Male adult rats (8 to 12 weeks old) were used for immunocytochemistry.

RESULTS

The results showed that PE decreased VTA DA neuron body size in standardly housed rats. Moreover, there was a significant decrease in numbers of VTA microglial branches and junctions in PE rats, suggesting morphological activation of microglia and possible neuroinflammation. The PE effects on microglia were normalized by postnatal environmental intervention, which also decreased the numbers of microglial branches and junctions in control animals, possibly via reduced stress.

CONCLUSIONS

Our findings show an association between PE-induced morphological activation of microglia and impaired DA neuron morphology in the VTA. Importantly, postnatal environmental intervention rescues possible PE-induced microglial activation. These data support that environmental intervention can be effective in ameliorating cognitive and behavioral deficits associated with VTA DA neuron dysfunctions, such as attention deficits and increased addiction risk.

Prenatal Ethanol Exposure Leads to Attention Deficits in Both Male and Female Rats

BACKGROUND

Prenatal ethanol exposure (PE) causes multiple behavioral and cognitive deficits, collectively referred to as fetal alcohol spectrum disorders (FASD). Studies show that 49-94% of FASD children exhibit attention deficits, even when they have normal IQs or lack severe facial deformities, suggesting that attention deficits could be caused by even moderate prenatal exposure to alcohol, of which the underlying neural mechanisms are still unclear. A valid rodent model could help elucidate this phenomenon.

MATERIALS AND METHODS

A second-trimester equivalent binge drinking PE model was utilized. Pregnant Sprague Dawley rats were administered with 15% (w/v) ethanol (6 g/kg/day, via gastric gavage) during gestational days 8-20, and their offspring were the subjects in the present study. A modified 2-choice reaction time (2-CRT) task was used to illustrate possible attention deficits, including increased action impulsivity and lapses of attention. Enhanced impulsivity was reflected by more premature responses while increased lapses of attention were manifested as more incorrect responses and/or greater variability of reaction time, demonstrated by more skewed distributions of reaction time. Ten-week-old male and female rats were tested for three sessions following 16-19 days of training.

RESULTS

Our PE paradigm caused no major teratogenic effects. PE led to increased impulsivity exhibited as greater premature responses and augmented lapses of attention shown by greater skewnesses of reaction time distributions, relative to controls. The deficits were observed in both PE male and female rats. Interestingly, in males, the attention deficits were detected only when the 2-CRT task was relatively difficult whereas in females they were detected even when the task was at a less demanding level.

CONCLUSION

We show that the binge drinking pattern of PE led to attention deficits in both sexes of rats even though no major teratogenic effects were observed. Therefore, this rodent model can be used to study neural mechanisms underlying attention deficits caused by PE and to explore effective intervention approaches for FASD.

Prenatal and postnatal alcohol exposure increases vulnerability to cocaine addiction in adult mice

BACKGROUND AND PURPOSE

Alcohol exposure in utero may lead to a wide range of long-lasting morphological and behavioural deficiencies known as fetal alcohol spectrum disorders (FASD), associated with a higher risk of later developing neuropsychiatric disorders. However, little is known about the long-term consequences of cocaine use and abuse in individuals with FASD. This study aimed to investigate the effects of maternal binge alcohol drinking during prenatal and postnatal periods on cocaine reward-related behaviours in adult offspring.

EXPERIMENTAL APPROACH

Pregnant C57BL/6 female mice were exposed to an experimental protocol of binge alcohol consumption (drinking-in-the-dark test) from gestation to weaning. Male offspring were subsequently left undisturbed until reaching adulthood and were tested for cocaine-induced motivational responses (conditioned place preference, behavioural sensitization and operant self-administration). Protein expression of dopamine- and glutamate-related molecules was assessed following cocaine-induced reinstatement.

KEY RESULTS

The results show that prenatal and postnatal alcohol exposure enhanced the preference for the cocaine-paired chamber in the conditioned place preference test. Furthermore, early alcohol-exposed mice displayed attenuated cocaine-induced behavioural sensitization but also higher cocaine self-administration. Furthermore, alterations in glutamatergic excitability (GluA1/GluA2 ratio) and ΔFosB expression were found in the prefrontal cortex and the striatum of alcohol-exposed mice after cocaine-primed reinstatement.

CONCLUSION AND IMPLICATIONS

Our findings demonstrate that maternal binge-like alcohol consumption during gestation and lactation alters sensitivity to the reinforcing effects of cocaine in adult offspring mice. Together, such data suggest that prenatal and postnatal alcohol exposure may underlie an enhanced susceptibility of alcohol-exposed offspring to develop drug addiction later in adulthood.

Early exposure to environmental enrichment modulates the effects of prenatal ethanol exposure upon opioid gene expression and adolescent ethanol intake

Prenatal ethanol exposure (PEE) promotes ethanol consumption in the adolescent offspring accompanied by the transcriptional regulation of kappa opioid receptor (KOR) system genes. This study analysed if environmental enrichment (EE, from gestational day 20 to postnatal day 26) exerts protective effects upon PEE-modulation of gene expression, ethanol intake and anxiety responses. Pregnant rats were exposed to PEE (0.0 or 2.0 g/kg ethanol, gestational days 17-20) and subsequently the dam and offspring were reared under EE or standard conditions. PEE upregulated KOR mRNA levels in amygdala (AMY) and prodynorphin (PDYN) mRNA levels in ventral tegmental area (VTA) with the latter effect associated with lower DNA methylation at the gene promoter. These effects were normalized by exposure to EE. PEE modulated BDNF mRNA levels in VTA and Nucleus accumbens (AcbN), and EE mitigated the changes in AcbN. EE induced a protective effect on ethanol intake and preference, an effect more noticeable in males than in females, and in prenatal vehicle-treated (PV) than in PEE rats. The male offspring drank significantly less ethanol than the female offspring. The latter result suggests that the protective effect of EE on ethanol drinking may only emerge at lower levels of drinking. In the dams, PEE induced an upregulation of PDYN and KOR in AcbN. PDYN gene expression was normalized by exposure to EE. These results suggest that EE is a promising treatment to inhibit the effects of PEE. The results confirm that PEE effects are mediated by alterations in the transcriptional regulation of KOR system genes.

Striatal morphological and functional alterations induced by prenatal alcohol exposure

Prenatal alcohol exposure (PAE) is an insidious yet preventable cause of developmental disability. The prenatal stage is a critical period for brain development with the concurrence of high vulnerability to the acute and prolonged effects of PAE. There is substantial evidence from both human observations and laboratory experiments that PAE is a common risk factor that predisposes to an array of postnatal mental disorders, including emotional, cognitive, and motor deficits. Although it is well accepted that PAE causes substantial morbidity, available treatments are limited. One reason is the lack of sufficient understanding about the neuroalterations induced by PAE, and how these changes contribute to PAE-induced mental disorders. Among a number of brain structures that have been explored extensively in PAE, the striatum has attracted great attention in the last 20 years in the field of PAE neurobiology. Interestingly, in animal models, the striatum has been considered as a pivotal switch of brain dysfunction induced by PAE, such as addiction, anxiety, depression, and neurodegeneration. In this review, we focus on recent advances in the understanding of morphological and functional changes in brain regions related to alterations after PAE, in particular the striatum. Because this region is central for behavior, emotion and cognition, there is an urgent need for more studies to uncover the PAE-induced alterations at the circuit, neuronal, synaptic and molecular levels, which will not only improve our understanding of the neuroplasticity induced by PAE, but also provide novel biological targets to treat PAE-related mental disorders with translational significance.