Fetal alcohol exposure leads to abnormal olfactory bulb development and impaired odor discrimination in adult mice

Effects of prenatal alcohol exposure on the olfactory system development

Fetal Alcohol Spectrum Disorders (FASD), resulting from maternal alcohol consumption during pregnancy, are a prominent non-genetic cause of physical disabilities and brain damage in children. Alongside common symptoms like distinct facial features and neurocognitive deficits, sensory anomalies, including olfactory dysfunction, are frequently noted in FASD-afflicted children. However, the precise mechanisms underpinning the olfactory abnormalities induced by prenatal alcohol exposure (PAE) remain elusive. Utilizing rodents as a model organism with varying timing, duration, dosage, and administration routes of alcohol exposure, prior studies have documented impairments in olfactory system development caused by PAE. Many reported a reduction in the olfactory bulb (OB) volume accompanied by reduced OB neuron counts, suggesting the OB is a brain region vulnerable to PAE. In contrast, no significant olfactory system defects were observed in some studies, though subtle alterations might exist. These findings suggest that the timing, duration, and extent of fetal alcohol exposure can yield diverse effects on olfactory system development. To enhance comprehension of PAE-induced olfactory dysfunctions, this review summarizes key findings from previous research on the olfactory systems of offspring prenatally exposed to alcohol.

Sexual Dimorphism in the Expression of Cardiac and Hippocampal Renin-Angiotensin and Kallikrein–Kinin Systems in Offspring from Mice Exposed to Alcohol during Gestation

Prenatal alcohol exposure (PAE) impairs fetal development. Alcohol consumption was shown to modulate the renin–angiotensin system (RAS). This study aimed to analyze the effects of PAE on the expression of the renin–angiotensin system (RAS) and kallikrein–kinin system (KKS) peptide systems in the hippocampus and heart of mice of both sexes. C57Bl/6 mice were exposed to alcohol during pregnancy at a concentration of 10% (v/v). On postnatal day 45 (PN45), mouse hippocampi and left ventricles (LV) were collected and processed for messenger RNA (mRNA) expression of components of the RAS and KKS. In PAE animals, more pronounced expression of AT1 and ACE mRNAs in males and a restored AT2 mRNA expression in females were observed in both tissues. In LV, increased AT2, ACE2, and B2 mRNA expressions were also observed in PAE females. Furthermore, high levels of H2O2 were observed in males from the PAE group in both tissues. Taken together, our results suggest that modulation of the expression of these peptidergic systems in PAE females may make them less susceptible to the effects of alcohol.

Impact of Prenatal Alcohol Exposure on the Development and Myocardium of Adult Mice: Morphometric Changes, Transcriptional Modulation of Genes Related to Cardiac Dysfunction, and Antioxidant Cardioprotection

The impact of prenatal alcohol exposure (PAE) varies considerably between individuals, leading to morphological and genetic changes. However, minor changes usually go undetected in PAE children. We investigated PAE's effects on gene transcription of genes related to cardiac dysfunction signaling in mouse myocardium and morphological changes. C57Bl/6 mice were subjected to a 10% PAE protocol. In postnatal days 2 and 60 (PN2 and PN60), morphometric measurements in the offspring were performed. Ventricular samples of the heart were collected in PN60 from male offspring for quantification of mRNA expression of 47 genes of nine myocardial signal transduction pathways related to cardiovascular dysfunction. Animals from the PAE group presented low birth weight than the Control group, but the differences were abolished in adult mice. In contrast, the mice's size was similar in PN2; however, PAE mice were oversized at PN60 compared with the Control group. Cardiac and ventricular indexes were increased in PAE mice. PAE modulated the mRNA expression of 43 genes, especially increasing the expressions of genes essential for maladaptive tissue remodeling. PAE animals presented increased antioxidant enzyme activities in the myocardium. In summary, PAE animals presented morphometric changes, transcription of cardiac dysfunction-related genes, and increased antioxidant protection in the myocardium.

Behavioral and Gene Regulatory Responses to Developmental Drug Exposures in Zebrafish

Developmental consequences of prenatal drug exposure have been reported in many human cohorts and animal studies. The long-lasting impact on the offspring-including motor and cognitive impairments, cranial and cardiac anomalies and increased prevalence of ADHD-is a socioeconomic burden worldwide. Identifying the molecular changes leading to developmental consequences could help ameliorate the deficits and limit the impact. In this study, we have used zebrafish, a well-established behavioral and genetic model with conserved drug response and reward pathways, to identify changes in behavior and cellular pathways in response to developmental exposure to amphetamine, nicotine or oxycodone. In the presence of the drug, exposed animals showed altered behavior, consistent with effects seen in mammalian systems, including impaired locomotion and altered habituation to acoustic startle. Differences in responses seen following acute and chronic exposure suggest adaptation to the presence of the drug. Transcriptomic analysis of exposed larvae revealed differential expression of numerous genes and alterations in many pathways, including those related to cell death, immunity and circadian rhythm regulation. Differential expression of circadian rhythm genes did not correlate with behavioral changes in the larvae, however, two of the circadian genes, arntl2 and per2, were also differentially expressed at later stages of development, suggesting a long-lasting impact of developmental exposures on circadian gene expression. The immediate-early genes, egr1, egr4, fosab, and junbb, which are associated with synaptic plasticity, were downregulated by all three drugs and in situ hybridization showed that the expression for all four genes was reduced across all neuroanatomical regions, including brain regions implicated in reward processing, addiction and other psychiatric conditions. We anticipate that these early changes in gene expression in response to drug exposure are likely to contribute to the consequences of prenatal exposure and their discovery might pave the way to therapeutic intervention to ameliorate the long-lasting deficits.

Altering Cell-Cell Interaction in Prenatal Alcohol Exposure Models: Insight on Cell-Adhesion Molecules During Brain Development

Alcohol exposure during pregnancy disrupts the development of the brain and produces long lasting behavioral and cognitive impairments collectively known as Fetal Alcohol Spectrum Disorders (FASDs). FASDs are characterized by alterations in learning, working memory, social behavior and executive function. A large body of literature using preclinical prenatal alcohol exposure models reports alcohol-induced changes in architecture and activity in specific brain regions affecting cognition. While multiple putative mechanisms of alcohol’s long-lasting effects on morphology and behavior have been investigated, an area that has received less attention is the effect of alcohol on cell adhesion molecules (CAMs). The embryo/fetal development represents a crucial period for Central Nervous System (CNS) development during which the cell-cell interaction plays an important role. CAMs play a critical role in neuronal migration and differentiation, synaptic organization and function which may be disrupted by alcohol. In this review, we summarize the physiological structure and role of CAMs involved in brain development, review the current literature on prenatal alcohol exposure effects on CAM function in different experimental models and pinpoint areas needed for future study to better understand how CAMs may mediate the morphological, sensory and behavioral outcomes in FASDs.

Midline Thalamic Damage Associated with Alcohol-Use Disorders: Disruption of Distinct Thalamocortical Pathways and Function

The thalamus, a significant part of the diencephalon, is a symmetrical and bilateral central brain structure. The thalamus is subdivided into three major groups of nuclei based on their function: sensorimotor nuclei (or principal/relay nuclei), limbic nuclei and nuclei bridging these two domains. Anatomically, nuclei within the thalamus are described by their location, such as anterior, medial, lateral, ventral, and posterior. In this review, we summarize the role of medial and midline thalamus in cognition, ranging from learning and memory to flexible adaptation. We focus on the discoveries in animal models of alcohol-related brain damage, which identify the loss of neurons in the medial and midline thalamus as drivers of cognitive dysfunction associated with alcohol use disorders. Models of developmental ethanol exposure and models of adult alcohol-related brain damage and are compared and contrasted, and it was revealed that there are similar (anterior thalamus) and different (intralaminar [adult exposure] versus ventral midline [developmental exposure]) thalamic pathology, as well as disruptions of thalamo-hippocampal and thalamo-cortical circuits. The final part of the review summarizes approaches to recover alcohol-related brain damage and cognitive and behavioral outcomes. These approaches include pharmacological, nutritional and behavioral interventions that demonstrated the potential to mitigate alcohol-related damage. In summary, the medial/midline thalamus is a significant contributor to cognition function, which is also sensitive to alcohol-related brain damage across the life span, and plays a role in alcohol-related cognitive dysfunction.

Aversive Learning Deficits and Depressive-Like Behaviors Are Accompanied by an Increase in Oxidative Stress in a Rat Model of Fetal Alcohol Spectrum Disorders: The Protective Effect of Rapamycin

Fetal alcohol spectrum disorders (FASDs) are one of the most common consequences of ethanol exposure during pregnancy. In adulthood, these disorders can be manifested by learning and memory deficits and depressive-like behavior. Ethanol-induced oxidative stress may be one of the factors that induces FASD development. The mammalian target of the Rapamycin (mTOR) signaling pathway that acts via two distinct multiprotein complexes, mTORC1 and mTORC2, can affect oxidative stress. We investigated whether mTOR-dependent or mTOR-independent mechanisms are engaged in this phenomenon. Thus, Rapamycin—a selective inhibitor of mTORC1, Torin-2—a non-selective mTORC1/mTORC2 inhibitor, and FK-506—a drug that impacts oxidative stress in an mTOR-independent manner were used. Behavioral tests were performed in adult (PND60-65) rats using a passive avoidance (PA) task (aversive learning and memory) and forced swimming test (FST) (depressive-like behaviors). In addition, the biochemical parameters of oxidative stress, such as lipid peroxidation (LPO), as well as apurinic/apyrimidinic (AP)-sites were determined in the hippocampus and prefrontal cortex in adult (PND65) rats. The rat FASD model was induced by intragastric ethanol (5 g/kg/day) administration at postnatal day (PND)4–9 (an equivalent to the third trimester of human pregnancy). All substances (3 mg/kg) were given 30 min before ethanol. Our results show that neonatal ethanol exposure leads to deficits in context-dependent fear learning and depressive-like behavior in adult rats that were associated with increased oxidative stress parameters in the hippocampus and prefrontal cortex. Because these effects were completely reversed by Rapamycin, an mTORC1 inhibitor, this outcome suggests its usefulness as a preventive therapy in disorders connected with prenatal ethanol exposure.

A systematic-review of olfactory deficits in neurodevelopmental disorders: From mouse to human

Olfactory impairment is a common clinical motif across neurodevelopmental disorders, suggesting olfactory circuits are particularly vulnerable to disease processes and can provide insight into underlying disease mechanisms. The mouse olfactory bulb is an ideal model system to study mechanisms of neurodevelopmental disease due to its anatomical accessibility, behavioral relevance, ease of measuring circuit input and output, and the feature of adult neurogenesis. Despite the clinical relevance and experimental benefits, olfactory testing across animal models of neurodevelopmental disease has been inconsistent and non-standardized. Here we performed a systematic literature review of olfactory function testing in mouse models of neurodevelopmental disorders, and identified intriguing inconsistencies that include evidence for both increased and decreased acuity in odor detection in various mouse models of Autism Spectrum Disorder (ASD). Based on our identified gaps in the literature, we recommend direct comparison of different mouse models of ASD using standardized tests for odor detection and discrimination. This review provides a framework to guide future olfactory function testing in mouse models of neurodevelopmental diseases.

Moderate prenatal alcohol exposure alters the number and function of GABAergic interneurons in the murine orbitofrontal cortex

Exposure to alcohol during development produces Fetal Alcohol Spectrum Disorders (FASD), characterized by a wide range of effects that include deficits in multiple cognitive domains. Early identification and treatment of individuals with FASD remain a challenge because neurobehavioral alterations do not become a significant problem until late childhood and early adolescence. Understanding the mechanisms underlying low and moderate prenatal alcohol exposure (PAE) effects on behavior and cognition is essential for improved diagnosis and treatment. Here, we examined the functional and morphological changes in an area known to be involved in executive control, the orbitofrontal cortex (OFC). We found that a moderate PAE model, previously shown to impair behavioral flexibility and to alter OFC activity in vivo, produced moderate functional and morphological changes within the OFC of mice in vitro. Specifically, slice electrophysiological recordings of spontaneous inhibitory post-synaptic currents in OFC pyramidal neurons revealed a significant increase in the amplitude and area in PAE mice relative to controls. Immunohistochemistry uncovered an increase in calretinin-, but not somatostatin- or parvalbumin-expressing cortical interneurons in the OFC of PAE mice. Together, these data suggest that moderate prenatal alcohol exposure alters the disinhibitory function in the OFC, which may contribute to the executive function deficits associated with FASD.

Murine Models for the Study of Fetal Alcohol Spectrum Disorders: An Overview

Prenatal alcohol exposure is associated to different physical, behavioral, cognitive, and neurological impairments collectively known as fetal alcohol spectrum disorder. The underlying mechanisms of ethanol toxicity are not completely understood. Experimental studies during human pregnancy to identify new diagnostic biomarkers are difficult to carry out beyond genetic or epigenetic analyses in biological matrices. Therefore, animal models are a useful tool to study the teratogenic effects of alcohol on the central nervous system and analyze the benefits of promising therapies. Animal models of alcohol spectrum disorder allow the analysis of key variables such as amount, timing and frequency of ethanol consumption to describe the harmful effects of prenatal alcohol exposure. In this review, we aim to synthetize neurodevelopmental disabilities in rodent fetal alcohol spectrum disorder phenotypes, considering facial dysmorphology and fetal growth restriction. We examine the different neurodevelopmental stages based on the most consistently implicated epigenetic mechanisms, cell types and molecular pathways, and assess the advantages and disadvantages of murine models in the study of fetal alcohol spectrum disorder, the different routes of alcohol administration, and alcohol consumption patterns applied to rodents. Finally, we analyze a wide range of phenotypic features to identify fetal alcohol spectrum disorder phenotypes in murine models, exploring facial dysmorphology, neurodevelopmental deficits, and growth restriction, as well as the methodologies used to evaluate behavioral and anatomical alterations produced by prenatal alcohol exposure in rodents.

Preclinical methodological approaches investigating of the effects of alcohol on perinatal and adolescent neurodevelopment

Despite much evidence of its economic and social costs, alcohol use continues to increase. Much remains to be known as to the effects of alcohol on neurodevelopment across the lifespan and in both sexes. We provide a comprehensive overview of the methodological approaches to ethanol administration when using animal models (primarily rodent models) and their translational relevance, as well as some of the advantages and disadvantages of each approach. Special consideration is given to early developmental periods (prenatal through adolescence), as well as to the types of research questions that are best addressed by specific methodologies. The zebrafish is used increasingly in alcohol research, and how to use this model effectively as a preclinical model is reviewed as well.

Anxious Behavior of Adult CD1 Mice Perinatally Exposed to Low Concentrations of Ethanol Correlates With Morphological Changes in Cingulate Cortex and Amygdala

Perinatal ethanol (EtOH) exposure is associated with high incidence of behavioral disorders such as depression and anxiety. The cerebral areas related with these consequences involve the corticolimbic system, in particular the prefrontal cortex, hippocampus, amygdala, and cingulate cortex, although the latter has not been thoroughly studied yet. Different animal models of prenatal or perinatal EtOH exposure have reported morphofunctional alterations in the central nervous system, which could explain behavioral disorders along life; these results focus on youth and adolescents and are still controversial. In the light of these inconclusive results, the aim of this work was to analyze adult behavior in CD1 mice perinatally exposed to low concentrations of EtOH (PEE) during gestation and lactation, and describe the morphology of the cingulate cortex and amygdala with a view to establishing structure/function/behavior correlations. Primiparous CD1 female mice were exposed to EtOH 6% v/v for 20 days prior to mating and continued drinking EtOH 6% v/v during pregnancy and lactation. After weaning, male pups were fed food and water ad libitum until 77 days of age, when behavioral and morphological studies were performed. Mouse behavior was analyzed through light–dark box and open field tests. Parameters related to anxious behavior and locomotor activity revealed anxiogenic behavior in PEE mice. After behavioral studies, mice were perfused and neurons, axons, serotonin transporter, 5HT, CB1 receptor (CB1R) and 5HT1A receptor (5HT1AR) were studied by immunofluorescence and immunohistochemistry in brain sections containing cingulate cortex and amygdala. Cingulate cortex and amygdala cytoarchitecture were preserved in adult PEE mice, although a smaller number of neurons was detected in the amygdala. Cingulate cortex axons demonstrated disorganized radial distribution and reduced area. Serotonergic and endocannabinoid systems, both involved in anxious behavior, showed differential expression. Serotonergic afferents were lower in both brain areas of PEE animals, while 5HT1AR expression was lower in the cingulate cortex and higher in the amygdala. The expression of CB1R was lower only in the amygdala. In sum, EtOH exposure during early brain development induces morphological changes in structures of the limbic system and its neuromodulation, which persist into adulthood and may be responsible for anxious behavior.

Rescue of ethanol-induced FASD-like phenotypes via prenatal co-administration of choline

Maternal consumption of alcohol during pregnancy can generate a multitude of deficits in the offspring. Fetal Alcohol Spectrum Disorders, or FASD, describe a palette of potentially life-long phenotypes that result from exposure to ethanol during human gestation. There is no cure for FASD and cognitive-behavioral therapies typically have low success rates, especially in severe cases. The neocortex, responsible for complex cognitive and behavioral function, is altered by prenatal ethanol exposure (PrEE). Supplementation with choline, an essential nutrient, during the prenatal ethanol insult has been associated with a reduction of negative outcomes associated with PrEE. However, choline's ability to prevent deficits within the developing neocortex, as well as the underlying mechanisms, remain unclear. Here, we exposed pregnant mice to 25% ethanol in addition to a 642 mg/L choline chloride supplement throughout gestation to determine the impact of choline supplementation on neocortical and behavioral development in ethanol-exposed offspring. We found that concurrent choline supplementation prevented gross developmental abnormalities associated with PrEE including reduced body weight, brain weight, and cortical length as well as partially ameliorated PrEE-induced abnormalities in intraneocortical circuitry. Additionally, choline supplementation prevented altered expression of RZRβ and Id2, two genes implicated in postmitotic patterning of neocortex, and global DNA hypomethylation within developing neocortex. Lastly, choline supplementation prevented sensorimotor behavioral dysfunction and partially ameliorated increased anxiety-like behavior observed in PrEE mice, as assessed by the Suok and Ledge tests. Our results suggest that choline supplementation may represent a potent preventative measure for the adverse outcomes associated with PrEE.

Magnetic Resonance Imaging and Micro-Computed Tomography reveal brain morphological abnormalities in a mouse model of early moderate prenatal ethanol exposure

BACKGROUND

This study investigated the effects of early moderate prenatal ethanol exposure (PEE) on the brain in a mouse model that mimics a scenario in humans, whereby moderate daily drinking ceases after a woman becomes aware of her pregnancy.

METHODS

C57BL/6J pregnant mice were given 10% v/v ethanol from gestational day 0-8 in the drinking water. The male offspring were used for imaging. Anatomical and diffusion Magnetic Resonance Imaging were performed in vivo at postnatal day 28 (P28, adolescence) and P80 (adulthood). Micro-Computed Tomography was performed on fixed whole heads at P80. Tensor-based morphometry (TBM) was applied to detect alterations in brain structure and voxel-based morphometry (VBM) for skull morphology. Diffusion tensor and neurite orientation dispersion and density imaging models were used to detect microstructural changes. Neurofilament (NF) immunohistochemistry was used to validate findings by in vivo diffusion MRI.

RESULTS

TBM showed that PEE mice exhibited a significantly smaller third ventricle at P28 (family-wise error rate (FWE), p < 0.05). All other macro-structural alterations did not survive FWE corrections but when displayed with an uncorrected p < 0.005 showed multiple regional volume reductions and expansions, more prominently in the right hemisphere. PEE-induced gross volume changes included a bigger thalamus, hypothalamus and ventricles at P28, and bigger total brain volumes at both P28 and P80 (2-sample t-tests). Disproportionately smaller olfactory bulbs following PEE were revealed at both time-points. No alterations in diffusion parameters were detected, but PEE animals exhibited reduced NF positive staining in the thalamus and striatum and greater bone density in various skull regions.

CONCLUSION

Our results show that early moderate PEE can cause alterations in the brain that are detectable during development and adulthood.

Social deficits following embryonic ethanol exposure arise in post-larval zebrafish

Prenatal alcohol exposure is the leading cause of birth defects, collectively termed fetal alcohol spectrum disorders (FASD). In the United States and Canada, 1 in 100 children will be born with FASD. Some of the most commonly debilitating defects of FASD are in social behavior. Zebrafish are highly social animals, and embryonic ethanol exposure from 24 to 26 hours post-fertilization disrupts this social (shoaling) response in adult zebrafish. Recent findings have suggested that social behaviors are present in zebrafish larvae as young as 3 weeks, but how they relate to adult shoaling is unclear. We tested the same ethanol-exposed zebrafish for social impairments at 3 weeks then again at 16 weeks. At both ages, live conspecifics were used to elicit a social response. We did not find alcohol-induced differences in behavior in 3-week-old fish when they were able to see conspecifics. We do find evidence that control zebrafish are able to use nonvisual stimuli to detect conspecifics, and this behavior is disrupted in the alcohol-exposed fish. As adults, these fish displayed a significant decrease in social behavior when conspecifics are visible. This surprising finding demonstrates that the adult and larval social behaviors are, at least partly, separable. Future work will investigate the nature of these nonvisual cues and how the neurocircuitry differs between the larval and adult social behaviors.

Oxidative stress and DNA damage in the mechanism of fetal alcohol spectrum disorders

This review covers molecular mechanisms involving oxidative stress and DNA damage that may contribute to morphological and functional developmental disorders in animal models resulting from exposure to alcohol (ethanol, EtOH) in utero or in embryo culture. Components covered include: (a) a brief overview of EtOH metabolism and embryopathic mechanisms other than oxidative stress; (b) mechanisms within the embryo and fetal brain by which EtOH increases the formation of reactive oxygen species (ROS); (c) critical embryonic/fetal antioxidative enzymes and substrates that detoxify ROS; (d) mechanisms by which ROS can alter development, including ROS-mediated signal transduction and oxidative DNA damage, the latter of which leads to pathogenic genetic (mutations) and epigenetic changes; (e) pathways of DNA repair that mitigate the pathogenic effects of DNA damage; (f) related indirect mechanisms by which EtOH enhances risk, for example by enhancing the degradation of some DNA repair proteins; and, (g) embryonic/fetal pathways like NRF2 that regulate the levels of many of the above components. Particular attention is paid to studies in which chemical and/or genetic manipulation of the above mechanisms has been shown to alter the ability of EtOH to adversely affect development. Alterations in the above components are also discussed in terms of: (a) individual embryonic and fetal determinants of risk and (b) potential risk biomarkers and mitigating strategies. FASD risk is likely increased in progeny which/who are biochemically predisposed via genetic and/or environmental mechanisms, including enhanced pathways for ROS formation and/or deficient pathways for ROS detoxification or DNA repair.

Effects of prenatal alcohol exposure (PAE): insights into FASD using mouse models of PAE

The potential impact of prenatal alcohol exposure (PAE) varies considerably among exposed individuals, with some displaying serious alcohol-related effects and many others showing few or no overt signs of fetal alcohol spectrum disorder (FASD). In animal models, variables such as nutrition, genetic background, health, other drugs, and stress, as well as dosage, duration, and gestational timing of exposure to alcohol can all be controlled in a way that is not possible in a clinical situation. In this review we examine mouse models of PAE and focus on those with demonstrated craniofacial malformations, abnormal brain development, or behavioral phenotypes that may be considered FASD-like outcomes. Analysis of these data should provide a valuable tool for researchers wishing to choose the PAE model best suited to their research questions or to investigate established PAE models for FASD comorbidities. It should also allow recognition of patterns linking gestational timing, dosage, and duration of PAE, such as recognizing that binge alcohol exposure(s) during early gestation can lead to severe FASD outcomes. Identified patterns could be particularly insightful and lead to a better understanding of the molecular mechanisms underlying FASD.

Neurological and neuropsychological effects of low and moderate prenatal alcohol exposure

Several explanations for the diverse results in research on foetal alcohol spectrum disorders or alcohol-related neurodevelopmental disorder might be at hand: timing, amount and patterns of alcohol exposure, as well as complex epigenetic responses. The genetic background of the offspring and its interaction with other prenatal and post-natal environmental cues are likely also of importance. In the present report, key findings about the possible effects of low and moderate doses of maternal alcohol intake on the neuropsychological development of the offspring are reviewed and plausible mechanisms discussed. Special focus is put on the serotonergic system within developmental and gene-environment frameworks. The review also suggests guidelines for future studies and also summarizes some of to-be-answered questions of relevance to clinical practice. Contradictory findings and paucity of studies on the effects of exposure to low alcohol levels during foetal life for the offspring's neuropsychological development call for large prospective studies, as well as for studies including neuroimaging and multi-omics analyses to dissect the neurobiological underpinnings of alcohol exposure-related phenotypes and to identify biomarkers. Finally, it remains to be investigated whether any safe threshold of alcohol drinking during pregnancy can be identified.

Measuring Olfactory Processes in Mus musculus

This paper briefly reviews the literature that describes olfactory acuity and odour discrimination learning. The results of current studies that examined the role of the neurotransmitters noradrenalin and acetylcholine in odour discrimination learning are discussed as are those that investigated pattern recognition and models of human disease. The methodology associated with such work is also described and its role in creating disparate results assessed. Recommendations for increasing the reliability and validity of experiments so as to further our understanding of olfactory processes in both healthy mice and those modelling human disease are made throughout the paper.

Radiological studies of fetal alcohol spectrum disorders in humans and animal models: An updated comprehensive review

Fetal Alcohol Spectrum Disorders encompass a wide range of birth defects in children born to mothers who consumed alcohol during pregnancy. Typical mental impairments in FASD include difficulties in life adaptation and learning and memory, deficits in attention, visuospatial skills, language and speech disabilities, mood disorders and motor disabilities. Multimodal imaging methods have enabled in vivo studies of the teratogenic effects of alcohol on the central nervous system, giving more insight into the FASD phenotype. This paper offers an up-to-date comprehensive review of radiological findings in the central nervous system in studies of prenatal alcohol exposure in both humans and translational animal models, including Magnetic Resonance Imaging, Computed Tomography, Positron Emission Tomography, Single Photon Emission Tomography and Ultrasonography.

Prenatal alcohol exposure potentiates chronic neuropathic pain, spinal glial and immune cell activation and alters sciatic nerve and DRG cytokine levels

A growing body of evidence indicates that prenatal alcohol exposure (PAE) may predispose individuals to secondary medical disabilities later in life. Animal models of PAE reveal neuroimmune sequelae such as elevated brain astrocyte and microglial activation with corresponding region-specific changes in immune signaling molecules such as cytokines and chemokines. The aim of this study was to evaluate the effects of moderate PAE on the development and maintenance of allodynia induced by chronic constriction injury (CCI) of the sciatic nerve in adult male rat offspring. Because CCI allodynia requires the actions of glial cytokines, we analyzed lumbar spinal cord glial and immune cell surface markers indicative of their activation levels, as well as sciatic nerve and dorsal root ganglia (DRG) cytokines in PAE offspring in adulthood. While PAE did not alter basal sensory thresholds before or after sham manipulations, PAE significantly potentiated adult onset and maintenance of allodynia. Microscopic analysis revealed exaggerated astrocyte and microglial activation, while flow cytometry data demonstrated increased proportions of immune cells with cell surface major histocompatibility complex II (MHCII) and β-integrin adhesion molecules, which are indicative of PAE-induced immune cell activation. Sciatic nerves from CCI rats revealed that PAE potentiated the proinflammatory cytokines interleukin (IL)-1β, IL-6 and tumor necrosis factor-alpha (TNFα) protein levels with a simultaneous robust suppression of the anti-inflammatory cytokine, IL-10. A profound reduction in IL-10 expression in the DRG of PAE neuropathic rats was also observed. Taken together, our results provide novel insights into the vulnerability that PAE produces for adult-onset central nervous system (CNS) pathological conditions from peripheral nerve injury.

Prenatal Alcohol Exposure Affects Progenitor Cell Numbers in Olfactory Bulbs and Dentate Gyrus of Vervet Monkeys

Fetal alcohol exposure (FAE) alters hippocampal cell numbers in rodents and primates, and this may be due, in part, to a reduction in the number or migration of neuronal progenitor cells. The olfactory bulb exhibits substantial postnatal cellular proliferation and a rapid turnover of newly formed cells in the rostral migratory pathway, while production and migration of postnatal neurons into the dentate gyrus may be more complex. The relatively small size of the olfactory bulb, compared to the hippocampus, potentially makes this structure ideal for a rapid analysis. This study used the St. Kitts vervet monkey (Chlorocebus sabeus) to (1) investigate the normal developmental sequence of post-natal proliferation in the olfactory bulb and dentate gyrus and (2) determine the effects of naturalistic prenatal ethanol exposure on proliferation at three different ages (neonate, five months and two years). Using design-based stereology, we found an age-related decrease of actively proliferating cells in the olfactory bulb and dentate gyrus for both control and FAE groups. Furthermore, at the neonatal time point, the FAE group had fewer actively proliferating cells as compared to the control group. These data are unique with respect to fetal ethanol effects on progenitor proliferation in the primate brain and suggest that the olfactory bulb may be a useful structure for studies of cellular proliferation.

Spectrum of Clinical and Associated MR Imaging Findings in Children with Olfactory Anomalies

BACKGROUND AND PURPOSE

The olfactory apparatus, consisting of the bulb and tract, is readily identifiable on MR imaging. Anomalous development of the olfactory apparatus may be the harbinger of anomalies of the secondary olfactory cortex and associated structures. We report a large single-site series of associated MR imaging findings in patients with olfactory anomalies.

MATERIALS AND METHODS

A retrospective search of radiologic reports (2010 through 2014) was performed by using the keyword "olfactory"; MR imaging studies were reviewed for olfactory anomalies and intracranial and skull base malformations. Medical records were reviewed for clinical symptoms, neuroendocrine dysfunction, syndromic associations, and genetics.

RESULTS

We identified 41 patients with olfactory anomalies (range, 0.03-18 years of age; M/F ratio, 19:22); olfactory anomalies were bilateral in 31 of 41 patients (76%) and absent olfactory bulbs and olfactory tracts were found in 56 of 82 (68%). Developmental delay was found in 24 (59%), and seizures, in 14 (34%). Pituitary dysfunction was present in 14 (34%), 8 had panhypopituitarism, and 2 had isolated hypogonadotropic hypogonadism. CNS anomalies, seen in 95% of patients, included hippocampal dysplasia in 26, cortical malformations in 15, malformed corpus callosum in 10, and optic pathway hypoplasia in 12. Infratentorial anomalies were seen in 15 (37%) patients and included an abnormal brain stem in 9 and an abnormal cerebellum in 3. Four patients had an abnormal membranous labyrinth. Genetic testing was performed in 23 (56%) and findings were abnormal in 11 (48%).

CONCLUSIONS

Olfactory anomalies should prompt careful screening of the brain, skull base, and the pituitary gland for additional anomalies. Genetic testing should be considered.

Prenatal alcohol exposure selectively enhances young adult perceived pleasantness of alcohol odors

Prenatal alcohol exposure (PAE) can lead to life-long neurobehavioral and social problems that can include a greater likelihood of early use and/or abuse of alcohol compared to older teens and young adults without PAE. Basic research in animals demonstrates that PAE influences later postnatal responses to chemosensory cues (i.e., odor & taste) associated with alcohol. We hypothesized that PAE would be related to poorer abilities to identify odors of alcohol-containing beverages, and would alter perceived alcohol odor intensity and pleasantness. To address this hypothesis we examined responses to alcohol and other odors in a small sample of young adults with detailed prenatal histories of exposure to alcohol and other drugs. The key finding from our controlled analyses is that higher levels of PAE were related to higher relative ratings of pleasantness for alcohol odors. As far as we are aware, this is the first published study to report the influence of PAE on responses to alcohol beverage odors in young adults. These findings are consistent with the hypothesis that positive associations (i.e., "pleasantness") to the chemosensory properties of alcohol (i.e., odor) are acquired prenatally and are retained for many years despite myriad interceding postnatal experiences. Alternate hypotheses may also be supported by the results. There are potential implications of altered alcohol odor responses for understanding individual differences in initiation of drinking, and alcohol seeking and high-risk alcohol-related behaviors in young adults.

Early maternal alcohol consumption alters hippocampal DNA methylation, gene expression and volume in a mouse model

The adverse effects of alcohol consumption during pregnancy are known, but the molecular events that lead to the phenotypic characteristics are unclear. To unravel the molecular mechanisms, we have used a mouse model of gestational ethanol exposure, which is based on maternal ad libitum ingestion of 10% (v/v) ethanol for the first 8 days of gestation (GD 0.5-8.5). Early neurulation takes place by the end of this period, which is equivalent to the developmental stage early in the fourth week post-fertilization in human. During this exposure period, dynamic epigenetic reprogramming takes place and the embryo is vulnerable to the effects of environmental factors. Thus, we hypothesize that early ethanol exposure disrupts the epigenetic reprogramming of the embryo, which leads to alterations in gene regulation and life-long changes in brain structure and function. Genome-wide analysis of gene expression in the mouse hippocampus revealed altered expression of 23 genes and three miRNAs in ethanol-exposed, adolescent offspring at postnatal day (P) 28. We confirmed this result by using two other tissues, where three candidate genes are known to express actively. Interestingly, we found a similar trend of upregulated gene expression in bone marrow and main olfactory epithelium. In addition, we observed altered DNA methylation in the CpG islands upstream of the candidate genes in the hippocampus. Our MRI study revealed asymmetry of brain structures in ethanol-exposed adult offspring (P60): we detected ethanol-induced enlargement of the left hippocampus and decreased volume of the left olfactory bulb. Our study indicates that ethanol exposure in early gestation can cause changes in DNA methylation, gene expression, and brain structure of offspring. Furthermore, the results support our hypothesis of early epigenetic origin of alcohol-induced disorders: changes in gene regulation may have already taken place in embryonic stem cells and therefore can be seen in different tissue types later in life.

Posttraining ablation of adult-generated olfactory granule cells degrades odor-reward memories

Proliferation of neural progenitor cells in the subventricular zone leads to the continuous generation of new olfactory granule cells (OGCs) throughout life. These cells synaptically integrate into olfactory bulb circuits after ∼2 weeks and transiently exhibit heightened plasticity and responses to novel odors. Although these observations suggest that adult-generated OGCs play important roles in olfactory-related memories, global suppression of olfactory neurogenesis does not typically prevent the formation of odor-reward memories, perhaps because residual OGCs can compensate. Here, we used a transgenic strategy to selectively ablate large numbers of adult-generated OGCs either before or after learning in mice. Consistent with previous studies, pretraining ablation of adult-generated OGCs did not prevent the formation of an odor-reward memory, presumably because existing OGCs can support memory formation in their absence. However, ablation of a similar cohort of adult-generated OGCs after training impaired subsequent memory expression, indicating that if these cells are available at the time of training, they play an essential role in subsequent expression of odor-reward memories. Memory impairment was associated with the loss of adult-generated OGCs that were >10 d in age and did not depend on the developmental stage in which they were generated, suggesting that, once sufficiently mature, OGCs generated during juvenility and adulthood play similar roles in the expression of odor-reward memories. Finally, ablation of adult-generated OGCs 1 month after training did not produce amnesia, indicating that adult-generated OGCs play a time-limited role in the expression of odor-reward memories.

Alcohol exposure inhibits adult neural stem cell proliferation

Alcohol exposure can reduce adult proliferation and/or neurogenesis, but its impact on the ultimate neurogenic precursors, neural stem cells (NSCs), has been poorly addressed. Accordingly, the impact of voluntary consumption of alcohol on NSCs in the subventricular zone (SVZ) of the lateral ventricle was examined in this study. The NSC population in adult male C57BL/6J mice was measured after voluntary alcohol exposure in a two-bottle choice task using the neurosphere assay, while the number of NSCs that had proliferated 2 weeks prior to tissue collection was indexed using bromodeoxyuridine (BrdU) retention. There was a significant decrease in the number of BrdU-retaining cells in alcohol-consuming mice compared with controls, but no difference in the number of neurosphere-forming cells that could be derived from the SVZ of alcohol-consuming mice compared with controls. Additionally, PCNA-labeled cells in the SVZ tended to be lower, but there was no difference in BrdU labeling in the dentate gyrus following alcohol exposure. To determine alcohol's direct impact on NSCs and their progeny, neurospheres derived from naïve mice were treated with alcohol in vitro. Neurosphere formation was reduced by 100 mM alcohol without reducing cell viability. These findings are the first to assess the impact of moderate voluntary alcohol consumption on selective measures of adult NSCs and indicate that such exposure alters NSC proliferation dynamics in vivo and alcohol has direct but dissociable effects on the expansion and viability on NSCs and their progeny in vitro.

Cortical odor processing in health and disease

The olfactory system has a rich cortical representation, including a large archicortical component present in most vertebrates, and in mammals neocortical components including the entorhinal and orbitofrontal cortices. Together, these cortical components contribute to normal odor perception and memory. They help transform the physicochemical features of volatile molecules inhaled or exhaled through the nose into the perception of odor objects with rich associative and hedonic aspects. This chapter focuses on how olfactory cortical areas contribute to odor perception and begins to explore why odor perception is so sensitive to disease and pathology. Odor perception is disrupted by a wide range of disorders including Alzheimer's disease, Parkinson's disease, schizophrenia, depression, autism, and early life exposure to toxins. This olfactory deficit often occurs despite maintained functioning in other sensory systems. Does the unusual network of olfactory cortical structures contribute to this sensitivity?

A comparison of the different animal models of fetal alcohol spectrum disorders and their use in studying complex behaviors

Prenatal ethanol exposure (PNEE) has been linked to widespread impairments in brain structure and function. There are a number of animal models that are used to study the structural and functional deficits caused by PNEE, including, but not limited to invertebrates, fish, rodents, and non-human primates. Animal models enable a researcher to control important variables such as the route of ethanol administration, as well as the timing, frequency and amount of ethanol exposure. Each animal model and system of exposure has its place, depending on the research question being undertaken. In this review, we will examine the different routes of ethanol administration and the various animal models of fetal alcohol spectrum disorders (FASD) that are commonly used in research, emphasizing their strengths and limitations. We will also present an up-to-date summary on the effects of prenatal/neonatal ethanol exposure on behavior across the lifespan, focusing on learning and memory, olfaction, social, executive, and motor functions. Special emphasis will be placed where the various animal models best represent deficits observed in the human condition and offer a viable test bed to examine potential therapeutics for human beings with FASD.

Adolescents' use of alcohol, tobacco and illicit drugs in relation to prenatal alcohol exposure: modifications by gender and ethnicity

AIMS

The study aimed to investigate (a) the association between low to moderate prenatal alcohol exposure (PAE) and the use of alcohol, tobacco and illicit drugs in adolescence and (b) whether the associations are modified by gender and ethnicity.

METHODS

The subjects of the study were 5922 children and adolescents, aged from 11 to 17 years, enrolled in the cross-sectional German Health Interview and Examination Survey for Children and Adolescents (the KiGGS study). Information on PAE is based on parental self-report questionnaires. Use of alcohol, tobacco and illicit drugs was assessed through self-report questionnaires for adolescents.

RESULTS

Low to moderate PAE was associated with an increased risk of drinking alcohol (adjusted odds ratio (OR) 1.73, 95% confidence interval (CI) 1.34, 2.18) and also of illicit drug use (adjusted OR 1.62, 95% CI 1.23, 2.14). The associations between PAE and the use of alcohol, tobacco and illicit drugs differed according to gender and ethnicity. Gender-stratified analyses resulted in adverse effects of PAE on drinking alcohol, smoking and illicit drug use in females; however, in German males, the associations disappeared. Stronger associations between PAE and the outcome measures were found in non-Germans.

CONCLUSIONS

Our findings indicate that low to moderate levels of maternal alcohol intake during pregnancy are a risk factor for use of alcohol, tobacco and illicit drugs by the offspring, with stronger associations in females and non-Germans.

The effects of chronic alcoholism on cell proliferation in the human brain

Neurogenesis continues in the human subventricular zone and to a lesser extent in the hippocampal subgranular zone throughout life. Subventricular zone-derived neuroblasts migrate to the olfactory bulb where survivors become integrated as interneurons and are postulated to contribute to odor discrimination. Adult neurogenesis is dysregulated in many neurological, neurovascular and neurodegenerative diseases. Alcohol abuse can result in a neurodegenerative condition called alcohol-related brain damage. Alcohol-related brain damage manifests clinically as cognitive dysfunction and the loss of smell sensation (hyposmia) and pathologically as generalized white matter atrophy and focal neuronal loss. The exact mechanism linking chronic alcohol intoxication with alcohol-related brain damage remains largely unknown but rodent models suggest that decreased neurogenesis is an important component. We investigated this idea by comparing proliferative events in the subventricular zone and olfactory bulb of a well-characterized cohort of 15 chronic alcoholics and 16 age-matched controls. In contrast to the findings in animal models there was no difference in the number of proliferative cell nuclear antigen-positive cells in the subventricular zone of alcoholics (mean±SD=28.7±20.0) and controls (27.6±18.9, p=1.0). There were also no differences in either the total (p=0.89) or proliferative cells (p=0.98) in the granular cell layer of the olfactory bulb. Our findings show that chronic alcohol consumption does not affect cell proliferation in the human SVZ or olfactory bulb. In fact only microglial proliferation could be demonstrated in the latter. Therefore neurogenic deficits are unlikely to contribute to hyposmia in chronic alcoholics.

Prenatal stress inhibits hippocampal neurogenesis but spares olfactory bulb neurogenesis

The dentate gyrus (DG) and the olfactory bulb (OB) are two regions of the adult brain in which new neurons are integrated daily in the existing networks. It is clearly established that these newborn neurons are implicated in specific functions sustained by these regions and that different factors can influence neurogenesis in both structures. Among these, life events, particularly occurring during early life, were shown to profoundly affect adult hippocampal neurogenesis and its associated functions like spatial learning, but data regarding their impact on adult bulbar neurogenesis are lacking. We hypothesized that prenatal stress could interfere with the development of the olfactory system, which takes place during the prenatal period, leading to alterations in adult bulbar neurogenesis and in olfactory capacities. To test this hypothesis we exposed pregnant C57Bl/6J mice to gestational restraint stress and evaluated behavioral and anatomic consequences in adult male offspring.

We report that prenatal stress has no impact on adult bulbar neurogenesis, and does not alter olfactory functions in adult male mice. However, it decreases cell proliferation and neurogenesis in the DG of the hippocampus, thus confirming previous reports on rats. Altogether our data support a selective and cross-species long-term impact of prenatal stress on neurogenesis.

Fetal Alcohol Spectrum Disorder (FASD) Associated Neural Defects: Complex Mechanisms and Potential Therapeutic Targets

Fetal alcohol spectrum disorder (FASD), caused by prenatal alcohol exposure, can result in craniofacial dysmorphism, cognitive impairment, sensory and motor disabilities among other defects. FASD incidences are as high as 2% to 5 % children born in the US, and prevalence is higher in low socioeconomic populations. Despite various mechanisms being proposed to explain the etiology of FASD, the molecular targets of ethanol toxicity during development are unknown. Proposed mechanisms include cell death, cell signaling defects and gene expression changes. More recently, the involvement of several other molecular pathways was explored, including non-coding RNA, epigenetic changes and specific vitamin deficiencies. These various pathways may interact, producing a wide spectrum of consequences. Detailed understanding of these various pathways and their interactions will facilitate the therapeutic target identification, leading to new clinical intervention, which may reduce the incidence and severity of these highly prevalent preventable birth defects. This review discusses manifestations of alcohol exposure on the developing central nervous system, including the neural crest cells and sensory neural placodes, focusing on molecular neurodevelopmental pathways as possible therapeutic targets for prevention or protection.

Emodin prevents ethanol-induced developmental anomalies in cultured mouse fetus through multiple activities

BACKGROUND

Maternal alcohol ingestion on pregnant period causes fetal alcohol syndrome including psychological and behavioral problems, and developmental abnormality. In this study, we investigated the effect of emodin, an active anthraquinone component found in the roots and bark of the genus Rhamnus (Buckthorn), on ethanol-induced teratogenesis during embryonic organogenesis.

METHODS

We cultured mouse embryos on embryonic day 8.5 for 2 days with ethanol (5 μl/3 ml) and/or emodin (1×10(-5) and 1×10(-4) μg/ml) using a whole embryo culture system and then investigated the developmental evaluation, superoxide dismutase (SOD) activity, and expression patterns of cytoplasmic SOD (SOD1), mitochondrial SOD (SOD2), cytosolic glutathione peroxidase (cGPx), tumor necrosis factor-α (TNF-α), caspase 3, and hypoxia inducible factor 1α (HIF-1α).

RESULTS

Morphological parameters, including growth in yolk sac and fetal head, body length, and development of the central nervous system, circulation system, sensory organs, skeletal system, and limbs in embryos exposed to ethanol were significantly decreased compared to those of the normal control group, but co-treatment with emodin (1 × 10(-5) and 1 × 10(-4) μg/ml) significantly improved these parameters. Furthermore, the reduced levels of SOD activity, and SOD1, SOD2, cGPx, and HIF-1α and the increased gene levels of TNF-α and caspase-3 due to ethanol exposure were significantly restored by cotreatment with emodin. Birth Defects Res (Part B) 98:268-275, 2013. © 2013 Wiley Periodicals, Inc.

CONCLUSIONS

This study revealed that cotreatment with emodin significantly prevented teratogenesis induced by ethanol, not only by modulating hypoxia and antioxidant enzymes, but also by attenuating the enhanced levels of TNF-α and caspase 3 in cultured embryos. Therefore, emodin may be an effective preventive agent for ethanol-induced teratogenesis.

Long-lasting neural circuit dysfunction following developmental ethanol exposure

Fetal Alcohol Spectrum Disorder (FASD) is a general diagnosis for those exhibiting long-lasting neurobehavioral and cognitive deficiencies as a result of fetal alcohol exposure. It is among the most common causes of mental deficits today. Those impacted are left to rely on advances in our understanding of the nature of early alcohol-induced disorders toward human therapies. Research findings over the last decade have developed a model where ethanol-induced neurodegeneration impacts early neural circuit development, thereby perpetuating subsequent integration and plasticity in vulnerable brain regions. Here we review our current knowledge of FASD neuropathology based on discoveries of long-lasting neurophysiological effects of acute developmental ethanol exposure in animal models. We discuss the important balance between synaptic excitation and inhibition in normal neural network function, and relate the significance of that balance to human FASD as well as related disease states. Finally, we postulate that excitation/inhibition imbalance caused by early ethanol-induced neurodegeneration results in perturbed local and regional network signaling and therefore neurobehavioral pathology.

Ontogeny of contextual fear memory formation, specificity, and persistence in mice

Pinpointing the precise age when young animals begin to form memories of aversive events is valuable for understanding the onset of anxiety and mood disorders and for detecting early cognitive impairment in models of childhood-onset disorders. Although these disorders are most commonly modeled in mice, we know little regarding the development of learning and memory in this species because most previous studies have been restricted to rats. Therefore, in the present study, we constructed an ontogenetic timeline of contextual fear memory ranging from infancy to adulthood in mice. We found that the ability of mice to form long-term context-shock associations emerged ∼13-14 d of age, which is several days earlier than previously reported for rats. Although the ability to form contextual fear memories remained stable from infancy into adulthood, infant mice had shorter-lasting memories than adolescent and adult mice. Furthermore, we found that mice subjected to fetal alcohol exposure showed a delay in the developmental emergence of contextual fear memory, illustrating the utility of this ontogenetic approach in detecting developmental delays in cognitive function stemming from maladaptive early life experience.

Ethanol-induced face-brain dysmorphology patterns are correlative and exposure-stage dependent

Prenatal ethanol exposure is the leading preventable cause of congenital mental disability. Whereas a diagnosis of fetal alcohol syndrome (FAS) requires identification of a specific pattern of craniofacial dysmorphology, most individuals with behavioral and neurological sequelae of heavy prenatal ethanol exposure do not exhibit these defining facial characteristics. Here, a novel integration of MRI and dense surface modeling-based shape analysis was applied to characterize concurrent face-brain phenotypes in C57Bl/6J fetuses exposed to ethanol on gestational day (GD)7 or GD8.5. The facial phenotype resulting from ethanol exposure depended upon stage of insult and was predictive of unique patterns of corresponding brain abnormalities. Ethanol exposure on GD7 produced a constellation of dysmorphic facial features characteristic of human FAS, including severe midfacial hypoplasia, shortening of the palpebral fissures, an elongated upper lip, and deficient philtrum. In contrast, ethanol exposure on GD8.5 caused mild midfacial hypoplasia and palpebral fissure shortening, a shortened upper lip, and a preserved philtrum. These distinct, stage-specific facial phenotypes were associated with unique volumetric and shape abnormalities of the septal region, pituitary, and olfactory bulbs. By demonstrating that early prenatal ethanol exposure can cause more than one temporally-specific pattern of defects, these findings illustrate the need for an expansion of current diagnostic criteria to better capture the full range of facial and brain dysmorphology in fetal alcohol spectrum disorders.

Does moderate drinking harm the fetal brain? Insights from animal models

Although public health campaigns advise pregnant women to abstain from ethanol, drinking during pregnancy is pervasive. Here, we highlight recent studies that have clearly demonstrated long-lasting neurobehavioral deficits in the offspring of laboratory animals exposed to moderate levels of ethanol during development. Alterations in learning, memory, motor coordination, social behavior, and stress responses were identified in these animals. Increased vulnerability to substance abuse was also demonstrated. These behavioral alterations have been associated with impairments in neurotransmitter systems, neuromodulators, and/or synaptic plasticity in several brain regions. With this review we hope to contribute to a better appreciation of the potential effects of developmental exposure to moderate ethanol levels, leading to better interventions aimed at relieving fetal alcohol spectrum disorders.

Lithium prevents long-term neural and behavioral pathology induced by early alcohol exposure

Fetal alcohol exposure can cause developmental defects in offspring known as fetal alcohol spectrum disorder (FASD). FASD symptoms range from obvious facial deformities to changes in neuroanatomy and neurophysiology that disrupt normal brain function and behavior. Ethanol exposure at postnatal day 7 in C57BL/6 mice induces neuronal cell death and long-lasting neurobehavioral dysfunction. Previous work has demonstrated that early ethanol exposure impairs spatial memory task performance into adulthood and perturbs local and interregional brain circuit integrity in the olfacto-hippocampal pathway. Here we pursue these findings to examine whether lithium prevents anatomical, neurophysiological, and behavioral pathologies that result from early ethanol exposure. Lithium has neuroprotective properties that have been shown to prevent ethanol-induced apoptosis. Here we show that mice co-treated with lithium on the same day as ethanol exposure exhibit dramatically reduced acute neurodegeneration in the hippocampus and retain hippocampal-dependent spatial memory as adults. Lithium co-treatment also blocked ethanol-induced disruption in synaptic plasticity in slice recordings of hippocampal CA1 in the adult mouse brain. Moreover, long-lasting dysfunctions caused by ethanol in olfacto-hippocampal networks, including sensory-evoked oscillations and resting state coherence, were prevented in mice co-treated with lithium. Together, these results provide behavioral and physiological evidence that lithium is capable of preventing or reducing immediate and long-term deleterious consequences of early ethanol exposure on brain function.