Selective effects of perinatal ethanol exposure in medial prefrontal cortex and nucleus accumbens

Gestational ethanol exposure impairs motor skills in female mice through dysregulated striatal dopamine and acetylcholine function

Fetal alcohol exposure has deleterious consequences on the motor skills of patients affected by Fetal Alcohol Spectrum Disorder (FASD) and in pre-clinical models of gestational ethanol exposure (GEE). Deficits in striatal cholinergic interneurons (CINs) and dopamine function impair action learning and execution, yet the effects of GEE on acetylcholine (ACh) and striatal dopamine release remain unexplored. Here, we report that alcohol exposure during the first ten postnatal days (GEEP0-P10), which mimics ethanol consumption during the last gestational trimester in humans, induces sex-specific anatomical and motor skill deficits in female mice during adulthood. Consistent with these behavioral impairments, we observed increased stimulus evoked-dopamine levels in the dorsolateral striatum (DLS) of GEEP0-P10 female, but not male, mice. Further experiments revealed sex-specific deficits in β2-containing nicotinic ACh receptor (nAChR)-modulation of electrically evoked dopamine release. Moreover, we found a reduced decay of ACh transients and a decreased excitability of striatal CINs in DLS of GEEP0-P10 females, indicating striatal CIN dysfunctions. Finally, the administration of varenicline, a β2-containing nAChR partial agonist, and chemogenetic-mediated increase in CIN activity improved motor performance in adult GEEP0-P10 females. Altogether, these data shed new light on GEE-induced striatal deficits and establish potential pharmacological and circuit-specific interventions to ameliorate motor symptoms of FASD.

Cannabidiol repairs behavioral and brain disturbances in a model of fetal alcohol spectrum disorder

Fetal alcohol spectrum disorder (FASD) includes neuropsychiatric disturbances related to gestational and lactational ethanol exposure. Available treatments are minimal and do not modulate ethanol-induced damage. Developing animal models simulating FASD is essential for understanding the underlying brain alterations and searching for efficient therapeutic approaches. The main goal of this study was to evaluate the effects of early and chronic cannabidiol (CBD) administration on offspring exposed to an animal model of FASD. Ethanol gavage (3 g/kg/12 h, p.o.) was administered to C57BL/6 J female mice, with a previous history of alcohol consumption, between gestational day 7 and postnatal day 21. On the weaning day, pups were separated by sex, and CBD administration began (30 mg/kg/day, i.p.). After 4-6 weeks of treatment, behavioral and neurobiological changes were analyzed. Mice exposed to the animal model of FASD showed higher anxiogenic and depressive-like behaviors and cognitive impairment that were evaluated through several experimental tests. These behaviors were accompanied by alterations in the gene, cellular and metabolomic targets. CBD administration normalized FASD model-induced emotional and cognitive disturbances, gene expression, and cellular changes with sex-dependent differences. CBD modulates the metabolomic changes detected in the hippocampus and prefrontal cortex. Interestingly, no changes were found in mitochondria or the oxidative status of the cells. These results suggest that the early and repeated administration of CBD modulated the long-lasting behavioral, gene and protein alterations induced by the FASD model, encouraging the possibility of performing clinical trials to evaluate the effects of CBD in children affected with FASD.

Moderate prenatal alcohol exposure produces sex-specific social impairments and attenuates prelimbic excitability and amygdala-cortex modulation of adult social behaviour

Lifelong social impairments are common in individuals with prenatal alcohol exposure (PAE), and preclinical studies have identified gestational day (G)12 as a vulnerable timepoint for producing social deficits following binge-level PAE. While moderate (m)PAE also produces social impairments, the long-term neuroadaptations underlying them are poorly understood. Activity of the projection from the basolateral amygdala to the prelimbic cortex (BLA → PL) leads to social avoidance, and the PL is implicated in negative social behaviours, making each of these potential candidates for the neuroadaptations underlying mPAE-induced social impairments. To examine this, we first established that G12 mPAE produced sex-specific social impairments lasting into adulthood in Sprague-Dawley rats. We then chemogenetically inhibited the BLA → PL using clozapine N-oxide (CNO) during adult social testing. This revealed that CNO reduced social investigation in control males but had no effect on mPAE males or females of either exposure, indicating that mPAE attenuated the role of this projection in regulating male social behaviour and highlighting one potential mechanism by which mPAE affects male social behaviour more severely. Using whole-cell electrophysiology, we also examined mPAE-induced changes to PL pyramidal cell physiology and determined that mPAE reduced cell excitability, likely due to increased suppression by inhibitory interneurons. Overall, this work identified two mPAE-induced neuroadaptations that last into adulthood and that may underlie the sex-specific vulnerability to mPAE-induced social impairments. Future research is necessary to expand upon how these circuits modulate both normal and pathological social behaviours and to identify sex-specific mechanisms, leading to differential vulnerability in males and females.

Representation of prefrontal axonal efferents in the thalamic nucleus reuniens in a rodent model of fetal alcohol exposure during third trimester

Alcohol exposure (AE) during the prenatal period could result in fetal alcohol spectrum disorders (FASDs), one of many deficits of which is impaired executive functioning (EF). EF relies on the coordination of activity between the medial prefrontal cortex (mPFC) and hippocampus (HPC) by the thalamic nucleus reuniens (Re), a structure that has been shown to be damaged following high-dose AE in a rodent model of third trimester exposure. Notably, mPFC neurons do not project directly to HPC, but rather communicate with it via a disynaptic pathway where the first cortical axons synapse on neurons in Re, which in turn send axons to make contacts with hippocampal cells. This experiment investigated the effect of binge AE (5.25 g/kg/day, two doses 2 h apart) during postnatal days 4–9 on the length of medial prefrontal axonal projections within Re in Long Evans rat. AE reduced the cumulative length of mPFC-originating axon terminals in Re in female rats, with male rats exhibiting shorter cumulative lengths when compared to female procedural control animals. Additionally, Re volume was decreased in AE animals, a finding that reproduced previously reported data. This experiment helps us better understand how early life AE affects prefrontal-thalamic-hippocampal connectivity that could underlie subsequent EF deficits.

Fluoxetine exposure throughout neurodevelopment differentially influences basilar dendritic morphology in the motor and prefrontal cortices

The significance of serotonin (5HT) in mental health is underscored by the serotonergic action of many classes of psychiatric medication. 5HT is known to have a significant role in neurodevelopment, thus 5HT disruption during development may have a long term impact on brain structure and circuits. We previously generated a model of 5HT alteration throughout neurodevelopment by maternal administration of the selective serotonin reuptake inhibitor fluoxetine. We found resulting social behavior alterations in the offspring during both postnatal and adult ages. Previous work by others has indicated that early 5HT disruption influences neuronal morphology. Therefore, in the current study we sought to determine if dendritic morphological changes occur in areas involved in the social behavior deficits we previously observed, specifically the primary motor (M1) and medial prefrontal (mPFC) cortices. We quantified dendritic morphology of projection neurons in M1 and mPFC at postnatal day (P)10 and P79 in mice exposed to fluoxetine. Basilar dendritic complexity and spine density were persistently decreased in M1 fluoxetine-exposed neurons while in the mPFC, similar reductions were observed at P79 but were not present at P10. Our findings underscore that the developing brain, specifically the projection cortex, is vulnerable to 5HT system perturbation, which may be related to later behavioral disruptions.

Corticostriatal Circuit Models of Cognitive Impairments Induced by Fetal Exposure to Alcohol

The term fetal alcohol spectrum disorder includes a group of diseases caused by fetal alcohol exposure (FAE). Patients with fetal alcohol spectrum disorder display heterogeneous socioemotional and cognitive deficits, particularly in the domain of executive function, that share symptoms with other neuropsychiatric disorders. Despite the availability of several preclinical models, the developmental brain defects causally linked to behavioral deficits induced by FAE remain poorly understood. Here, we first review the effects of FAE on corticostriatal development and its impact on both corticostriatal pathway function and cognitive abilities. We propose three non-mutually exclusive circuit models of corticostriatal dysfunctions to account for some of the FAE-induced cognitive deficits. One model posits that associative-sensorimotor imbalance causes hyper goal-directed behavior, and a second model implies that alteration of prefrontal-striatal behavioral suppression circuits results in loss of behavioral inhibition. A third model suggests that local striatal circuit deficits affect striatal neuronal ensemble function to impair action selection and performance. Finally, we discuss how preclinical approaches applied to these circuit models could offer potential rescue strategies for executive function deficits in patients with fetal alcohol spectrum disorder.

Maternal Ethanol Exposure Acutely Elevates Src Family Kinase Activity in the Fetal Cortex

Fetal alcohol syndrome (FAS) is characterized by disrupted fetal brain development and postnatal cognitive impairment. The targets of alcohol are diverse, and it is not clear whether there are common underlying molecular mechanisms producing these disruptions. Prior work established that acute ethanol exposure causes a transient increase in tyrosine phosphorylation of multiple proteins in cultured embryonic cortical cells. In this study, we show that a similar tyrosine phosphorylation transient occurs in the fetal brain after maternal dosing with ethanol. Using phospho-specific antibodies and immunohistochemistry, we mapped regions of highest tyrosine phosphorylation in the fetal cerebral cortex and found that areas of dendritic and axonal growth showed elevated tyrosine phosphorylation 10 min after maternal ethanol exposure. These were also areas of Src expression and Src family kinase (SFK) activation loop phosphorylation (pY416) expression. Importantly, maternal pretreatment with the SFK inhibitor dasatinib completely prevents both the pY416 increase and the tyrosine phosphorylation response. The phosphorylation response was observed in the perisomatic region and neurites of immature migrating and differentiating primary neurons. Importantly, the initial phosphotyrosine transient (~ 30 min) targets both Src and Dab1, two critical elements in Reelin signaling, a pathway required for normal cortical development. This initial phosphorylation response is followed by sustained reduction in Ser3 phosphorylation of n-cofilin, a critical actin severing protein and an identified downstream effector of Reelin signaling. This biochemical disruption is associated with sustained reduction of F-actin content and disrupted Golgi apparatus morphology in developing cortical neurons. The finding outlines a model in which the initial activation of SFKs by ethanol has the potential to disrupt multiple developmentally important signaling systems for several hours after maternal exposure.

Dynamics of microglia and dendritic spines in early adolescent cortex after developmental alcohol exposure

Fetal alcohol spectrum disorder patients suffer from many cognitive disabilities. These include impaired auditory, visual, and tactile sensory information processing, making it more difficult for these patients to learn to navigate social scenarios. Rodent studies have shown that alcohol exposure during the brain growth spurt (BGS) can lead to acute neuronal apoptosis and an immunological response by microglia in the somatosensory cortex. Since microglia have critical physiological functions, including the support of excitatory synapse remodeling via interactions with dendritic spines, we sought to understand whether BGS alcohol exposure has long-term effects on microglial or dendritic spine dynamics. Using in vivo two-photon microscopy in 4-5 week old mice, we evaluated microglial functions such as process motility, the response to tissue injury, and the dynamics of physical interactions between microglial processes and dendritic spines. We also investigated potential differences in the morphology, density, or dynamics of dendritic spines in layer I/II primary sensory cortex of control and BGS alcohol exposed mice. We found that microglial process motility and contact with dendritic spines were not altered after BGS alcohol exposure. While the response of microglial processes toward tissue injury was not significantly altered by prior alcohol exposure, there was a trend suggesting that alcohol early in life may prime microglia to respond more quickly to secondary injury. Spine density, morphology, stability, and remodeling over time were not perturbed after BGS alcohol exposure. We demonstrate that after BGS alcohol exposure, the physiological functions of microglia and excitatory neurons remain intact in early adolescence.

Executive functioning-specific behavioral impairments in a rat model of human third trimester binge drinking implicate prefrontal-thalamo-hippocampal circuitry in Fetal Alcohol Spectrum Disorders

Individuals diagnosed with Fetal Alcohol Spectrum Disorders (FASD) often display behavioral impairments in executive functioning (EF). Specifically, the domains of working memory, inhibition, and set shifting are frequently impacted by prenatal alcohol exposure. Coordination between prefrontal cortex and hippocampus appear to be essential for these domains of executive functioning. The current study uses a rodent model of human third-trimester binge drinking to identify the extent of persistent executive functioning deficits following developmental alcohol by using a behavioral battery of hippocampus- and prefrontal cortex-dependent behavioral assays in adulthood. Alcohol added to milk formula was administered to Long Evans rat pups on postnatal days 4-9 (5.25 g/kg/day of ethanol; intragastric intubation), a period when rodent brain development undergoes comparable processes to human third-trimester neurodevelopment. Procedural control animals underwent sham intubation, without administration of any liquids (i.e., alcohol, milk solution). In adulthood, male rats were run on a battery of behavioral assays: novel object recognition, object-in-place associative memory, spontaneous alternation, and behavioral flexibility tasks. Alcohol-exposed rats demonstrated behavioral impairment in object-in-place preference and performed worse when the rule was switched on a plus maze task. All rats showed similar levels of novel object recognition, spontaneous alternation, discrimination learning, and reversal learning, suggesting alcohol-induced behavioral alterations are selective to executive functioning domains of spatial working memory and set-shifting in this widely-utilized rodent model. These specific behavioral alterations support the hypothesis that behavioral impairments in EF following prenatal alcohol exposure are caused by distributed damage to the prefrontal-thalamo-hippocampal circuit consisting of the medial prefrontal cortex, thalamic nucleus reuniens, and CA1 of hippocampus.

Neurodevelopmental signatures of narcotic and neuropsychiatric risk factors in 3D human-derived forebrain organoids

It is widely accepted that narcotic use during pregnancy and specific environmental factors (e.g., maternal immune activation and chronic stress) may increase risk of neuropsychiatric illness in offspring. However, little progress has been made in defining human-specific in utero neurodevelopmental pathology due to ethical and technical challenges associated with accessing human prenatal brain tissue. Here we utilized human induced pluripotent stem cells (hiPSCs) to generate reproducible organoids that recapitulate dorsal forebrain development including early corticogenesis. We systemically exposed organoid samples to chemically defined "enviromimetic" compounds to examine the developmental effects of various narcotic and neuropsychiatric-related risk factors within tissue of human origin. In tandem experiments conducted in parallel, we modeled exposure to opiates (μ-opioid agonist endomorphin), cannabinoids (WIN 55,212-2), alcohol (ethanol), smoking (nicotine), chronic stress (human cortisol), and maternal immune activation (human Interleukin-17a; IL17a). Human-derived dorsal forebrain organoids were consequently analyzed via an array of unbiased and high-throughput analytical approaches, including state-of-the-art TMT-16plex liquid chromatography/mass-spectrometry (LC/MS) proteomics, hybrid MS metabolomics, and flow cytometry panels to determine cell-cycle dynamics and rates of cell death. This pipeline subsequently revealed both common and unique proteome, reactome, and metabolome alterations as a consequence of enviromimetic modeling of narcotic use and neuropsychiatric-related risk factors in tissue of human origin. However, of our 6 treatment groups, human-derived organoids treated with the cannabinoid agonist WIN 55,212-2 exhibited the least convergence of all groups. Single-cell analysis revealed that WIN 55,212-2 increased DNA fragmentation, an indicator of apoptosis, in human-derived dorsal forebrain organoids. We subsequently confirmed induction of DNA damage and apoptosis by WIN 55,212-2 within 3D human-derived dorsal forebrain organoids. Lastly, in a BrdU pulse-chase neocortical neurogenesis paradigm, we identified that WIN 55,212-2 was the only enviromimetic treatment to disrupt newborn neuron numbers within human-derived dorsal forebrain organoids. Cumulatively this study serves as both a resource and foundation from which human 3D biologics can be used to resolve the non-genomic effects of neuropsychiatric risk factors under controlled laboratory conditions. While synthetic cannabinoids can differ from naturally occurring compounds in their effects, our data nonetheless suggests that exposure to WIN 55,212-2 elicits neurotoxicity within human-derived developing forebrain tissue. These human-derived data therefore support the long-standing belief that maternal use of cannabinoids may require caution so to avoid any potential neurodevelopmental effects upon developing offspring in utero.

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.

Increased ethanol intake is associated with social anxiety in offspring exposed to ethanol on gestational day 12

Prenatal alcohol exposure (PAE) can result in physical, cognitive, and neurological deficits termed Fetal Alcohol Spectrum Disorder (FASD). Deficits in social functioning associated with PAE are frequently observed and persist throughout the lifespan. Social impairments, such as social anxiety, are associated with increased alcohol abuse, which is also highly pervasive following PAE. Yet, the relationship between PAE-induced social alterations and alcohol intake later in life is not well understood. In order to test this relationship, we exposed pregnant female Sprague Dawley rats to a single instance of PAE on gestational day 12, a period of substantial neural development, and tested offspring in adulthood (postnatal day 63) in a modified social interaction test followed by alternating alone and social ethanol intake sessions. Consistent with our previous findings, we found that, in general, PAE reduced social preference (measure of social anxiety-like behavior) in female but not male adults. However, ethanol intake was significantly higher in the PAE group regardless of sex. When dividing subjects according to level of social anxiety-like behavior (low, medium, or high), PAE males (under both drinking contexts) and control females (under the social drinking context) with a high social anxiety phenotype showed the highest level of ethanol intake. Taken together, these data indicate that PAE differentially affects the interactions between social anxiety, ethanol intake, and drinking context in males and females. These findings extend our understanding of the complexity and persistence of PAE's sex-dependent effects into adulthood.

Nucleus reuniens of the midline thalamus of a rat is specifically damaged after early postnatal alcohol exposure

Individuals diagnosed with fetal alcohol spectrum disorders often show behavioral impairments in executive functioning. Mechanistic studies have implicated coordination between the prefrontal cortex and the hippocampus (through thalamic nucleus reuniens) as essential for such executive functions. This study is the first to report the long-term neuroanatomical alterations to the ventral midline thalamus after alcohol exposure on postnatal days 4-9 (a rodent model of binge drinking during the third-trimester of human pregnancy). Alcohol added to a milk formula was administered to female Long-Evans rat pups on postnatal days 4-9 (5.25 g/kg/day of ethanol, intragastric intubation). Control animals were intubated without the administration of liquid. In adulthood, brains were immunohistochemically labeled for a neuronal marker (NeuN) conjugated with Cy3 fluorophore and stained with Hoechst33342 to visualize nuclei. Total non-neuronal cell number (NeuN/Hoechst) and neuron number (NeuN/Hoechst), and total volume were estimated using unbiased stereology in two neighboring midline thalamic nuclei: reuniens and rhomboid. Estimates were analyzed using linear mixed modeling to account for animal and litter as clustering variables. A 21% reduction in the total neuron number (resulting in altered neuron-to-non-neuron ratio) and an 18% reduction in total volume were found exclusively in thalamic nucleus reuniens in rats exposed to ethanol. Non-neuronal cell number was not changed in reuniens. No ethanol-induced changes on any measures were observed in rhomboid nucleus. These specific neuroanatomical alterations provide a necessary foundation for further examination of circuit-level alterations that occur in fetal alcohol spectrum disorder.

Cholinergic rescue of neurocognitive insult following third-trimester equivalent alcohol exposure in rats

Neonatal ethanol exposure during the third trimester equivalent of human pregnancy in the rat significantly impairs hippocampal and prefrontal neurobehavioral functioning. Postnatal day [PD] 4-9 ethanol exposure in rats disrupts long-term context memory formation, resulting in abolished post-shock and retention test freezing in a variant of contextual fear conditioning called the Context Preexposure Facilitation Effect (CPFE). This behavioral impairment is accompanied by disrupted medial prefrontal, but not dorsal hippocampal expression of the immediate early genes (IEGs) c-Fos, Arc, Egr-1, and Npas4 (Heroux, Robinson-Drummer, Kawan, Rosen, & Stanton, 2019). The current experiment examined if systemic administration of the acetylcholinesterase inhibitor physostigmine (PHY) prior to context learning would rescue prefrontal IEG expression and freezing in the CPFE. From PD4-9, Long-Evans rats received oral intubation of ethanol (EtOH; 5.25 g/kg/day) or sham-intubation (SI). Rats received a systemic injection of saline (SAL) or PHY (0.01 mg/kg) prior to all three phases (Experiment 1) or just context exposure (Experiment 2) in the CPFE from PD31-33. A subset of rats were sacrificed 30 min after context learning to assay changes in IEG expression in the medial prefrontal cortex (mPFC), dorsal hippocampus (dHPC), and ventral hippocampus (vHPC). Administration of PHY prior to all three phases or just context learning rescued both post-shock and retention test freezing in the CPFE in EtOH rats without altering performance in SI rats. EtOH-SAL rats had significantly reduced mPFC but not dHPC expression of c-Fos, Arc, Egr-1, and Npas4. EtOH-PHY treatment rescued mPFC expression of c-Fos in ethanol-exposed rats and increased Arc and Npas4 regardless of dosing condition. While there was no effect of PHY on dHPC or vHPC expression of Arc, Egr-1, or Npas4, this treatment significantly boosted hippocampal expression of c-Fos regardless of ethanol treatment. These findings implicate impaired cholinergic and prefrontal function in cognitive deficits arising from 3rd-trimester equivalent alcohol exposure.

Effects of neonatal ethanol on cerebral cortex development through adolescence

Neonatal brain lesions cause deficits in structure and function of the cerebral cortex that sometimes are not fully expressed until adolescence. To better understand the onset and persistence of changes caused by postnatal day 7 (P7) ethanol treatment, we examined neocortical cell numbers, volume, surface area and thickness from neonatal to post-adolescent ages. In control mice, total neuron number decreased from P8 to reach approximately stable levels at about P30, as expected from normal programmed cell death. Cortical thickness reached adult levels by P14, but cortical volume and surface area continued to increase from juvenile (P20-30) to post-adolescent (P54-93) ages. P7 ethanol caused a reduction of total neurons by P14, but this deficit was transient, with later ages having only small and non-significant reductions. Previous studies also reported transient neuron loss after neonatal lesions that might be partially explained by an acute acceleration of normally occurring programmed cell death. GABAergic neurons expressing parvalbumin, calretinin, or somatostatin were reduced by P14, but unlike total neurons the reductions persisted or increased in later ages. Cortical volume, surface area and thickness were also reduced by P7 ethanol. Cortical volume showed evidence of a transient reduction at P14, and then was reduced again in post-adolescent ages. The results show a developmental sequence of neonatal ethanol effects. By juvenile ages the cortex overcomes the P14 deficit of total neurons, whereas P14 GABA cell deficits persist. Cortical volume reductions were present at P14, and again in post-adolescent ages.

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.

Neonatal ethanol exposure impairs long-term context memory formation and prefrontal immediate early gene expression in adolescent rats

Fetal alcohol exposure leads to severe disruptions in learning and memory involving the hippocampus and prefrontal cortex in humans. Animal model research on FASD has documented impairment of hippocampal neuroanatomy and function but animal studies of cognition involving the prefrontal cortex are sparse. We have found that a variant of contextual fear conditioning in which both the hippocampus and prefrontal cortex is required, the Context Preexposure Facilitation Effect (CPFE), is particularly sensitive to neurobehavioral disruption caused by neonatal ethanol exposure during the third trimester equivalent of human pregnancy in the rat (i.e., PD4-9). In the CPFE, learning about the context, acquiring a context-shock association, and retrieving contextual fear are temporally separated across three days. The current study asked whether neonatal alcohol exposure impairs context learning, consolidation, or retrieval and examined prefrontal and hippocampal molecular signaling as correlates of this impairment. Long-Evans rats that received oral intubation of ethanol (AE; 5.25 g/kg/day, split into two doses) or underwent sham-intubation (SI) from PND4-9 were tested on the CPFE on PD31-33. Extending our previous reports, ethanol abolished both post-shock and retention test freezing in the CPFE. Assays (qPCR) of immediate early gene expression revealed that ethanol disrupted prefrontal but not hippocampal expression of c-Fos, Arc, Egr-1, and Npas4 during context learning. Finally, ethanol-exposed animals were unimpaired in a standard contextual fear conditioning procedure in which learning about the context and acquiring a context-shock association occurs concurrently. These findings implicate impaired prefrontal function in cognitive deficits arising from 3rd-trimester equivalent alcohol exposure in the rat.

Impairment of the context preexposure facilitation effect in juvenile rats by neonatal alcohol exposure is associated with decreased Egr-1 mRNA expression in the prefrontal cortex

The context preexposure facilitation effect (CPFE) is a variant of contextual fear conditioning in which learning about the context (preexposure) and associating the context with a shock (training) occur on separate occasions. The CPFE is sensitive to a range of neonatal alcohol doses (Murawski & Stanton, 2011). The current study examined the impact of neonatal alcohol on Egr-1 mRNA expression in the infralimbic (IL) and prelimbic (PL) subregions of the mPFC, the CA1 of dorsal hippocampus (dHPC), and the lateral nucleus of the amygdala (LA), following the preexposure and training phases of the CPFE. Rat pups were exposed to a 5.25 g/kg/day single binge-like dose of alcohol (Group EtOH) or were sham intubated (SI; Group SI) over postnatal days (PD) 7-9. In behaviorally tested rats, alcohol administration disrupted freezing. Following context preexposure, Egr-1 mRNA was elevated in both EtOH and SI groups compared with baseline control animals in all regions analyzed. Following both preexposure and training, Group EtOH displayed a significant decrease in mPFC Egr-1 mRNA expression compared with Group SI. However, this decrease was greatest after training. Training day decreases in Egr-1 expression were not found in LA or CA1 in Group EtOH compared with Group SI. A second experiment confirmed that the EtOH-induced training-day deficits in mPFC Egr-1 mRNA expression were specific to groups which learned contextual fear (vs. nonassociative controls). Thus, memory processes that engage the mPFC during the context-shock association may be most susceptible to the teratogenic effects of neonatal alcohol. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Prenatal alcohol exposure disrupts male adolescent social behavior and oxytocin receptor binding in rodents

Social behavior deficits resulting from prenatal alcohol exposure (PAE) emerge early in life and become more pronounced across development. Maturational changes associated with adolescence, including pubertal onset, can have significant consequences for social behavior development, making adolescence a unique period of increased vulnerability to social behavior dysfunction. Unfortunately, little is known about the underlying neurobiology supporting PAE-related social behavior impairments, particularly in the context of adolescence, when the transition to a more complex social environment may exacerbate existing deficits in social behavior function. Here we perform a comprehensive evaluation of social behavior development in PAE animals during two different periods in adolescence using three separate but related tests of social behavior in increasingly complex social contexts: the social interaction test, the social recognition memory test (i.e. habituation-dishabituation test), and the social discrimination test. Additionally, we investigated the underlying neurobiology of the oxytocin (OT) and vasopressin (AVP) systems following PAE, given their well-documented role in mediating social behavior. Our results demonstrate that compared to controls, early adolescent PAE animals showed impairments on the social recognition memory test and increased OT receptor binding in limbic networks, while late adolescent PAE animals exhibited impairments on the social discrimination test and increased OTR binding in forebrain reward systems. Taken together, these data indicate that PAE impairs adolescent social behavior - especially with increasing complexity of the social context - and that impairments are associated with altered development of the OT but not the AVP system.

Meta-Analyses of Externalizing Disorders: Genetics or Prenatal Alcohol Exposure?

BACKGROUND

Externalizing disorders are heritable precursors to alcohol dependence, common in children of alcoholics (COA), and in children with prenatal alcohol exposure (PAE). Pregnancies involving alcohol exposure sufficient to affect the fetus may involve women with genetic risk for alcohol dependence. We hypothesized that known PAE will increase the odds of having an externalizing disorder compared to COA.

METHODS

The odds ratios of 3 externalizing disorders (attention-deficit hyperactivity disorder [ADHD], conduct disorder [CD], and oppositional defiant disorder [ODD]) were obtained for 2 domains: (i) PAE and (ii) COA, by estimating the logged odds ratio (LOR) for each study. Permutation tests were implemented to compare LORs for PAE versus COA studies within each disorder, including PAE versus an alcohol dependent (AD) mother and PAE versus an AD father.

RESULTS

In PAE studies, the odds of ADHD and CD were elevated. Rates of all 3 disorders were elevated in COA studies. Permutation tests revealed that the mean LOR for ADHD was significantly higher in PAE studies compared to: COA (p = 0.01), AD mother (p < 0.05), and AD father (p = 0.03). No differences were found for ODD (p = 0.09) or CD (p = 0.21).

CONCLUSIONS

These results provide compelling evidence of an increased risk of ADHD in those with PAE beyond that due to parental alcohol dependence or a genetic liability, consistent with a unique etiology most likely due to direct alcohol exposure during prenatal development.

Developmental ethanol exposure alters the morphology of mouse prefrontal neurons in a layer-specific manner

Chronic developmental exposure to ethanol can lead to a wide variety of teratogenic effects, which in humans are known as fetal alcohol spectrum disorders (FASD). Individuals affected by FASD may exhibit persistent impairments to cognitive functions such as learning, memory, and attention, which are highly dependent on medial prefrontal cortex (mPFC) circuitry. The objective of this study was to determine long-term effects of chronic developmental ethanol exposure on mPFC neuron morphology, in order to better-understand potential neuronal mechanisms underlying cognitive impairments associated with FASD. C57BL/6-strain mice were exposed to ethanol or an isocaloric/isovolumetric amount of sucrose (control) via oral gavage, administered both to the dam from gestational day 10-18 and directly to pups from postnatal day 4-14. Brains from male mice were collected at postnatal day 90 and neurons were stained using a modified Golgi-Cox method. Pyramidal neurons within layers II/III, V and VI of the mPFC were imaged, traced in three dimensions, and assessed using Sholl and branch structure analyses. Developmental ethanol exposure differentially impacted adult pyramidal neuron morphology depending on mPFC cortical layer. Neurons in layer II/III exhibited increased size and diameter of dendrite trees, whereas neurons in layer V were not affected. Layer VI neurons with long apical dendrites had trees with decreased diameter that extended farther from the soma, and layer VI neurons with short apical dendrite trees exhibited decreased tree size overall. These layer-specific alterations to mPFC neuron morphology may form a novel morphological mechanism underlying long-term mPFC dysfunction and resulting cognitive impairments in FASD.

DNA Methylation program in normal and alcohol-induced thinning cortex

While cerebral underdevelopment is a hallmark of fetal alcohol spectrum disorders (FASD), the mechanism(s) guiding the broad cortical neurodevelopmental deficits are not clear. DNA methylation is known to regulate early development and tissue specification through gene regulation. Here, we examined DNA methylation in the onset of alcohol-induced cortical thinning in a mouse model of FASD. C57BL/6 (B6) mice were administered a 4% alcohol (v/v) liquid diet from embryonic (E) days 7-16, and their embryos were harvested at E17, along with isocaloric liquid diet and lab chow controls. Cortical neuroanatomy, neural phenotypes, and epigenetic markers of methylation were assessed using immunohistochemistry, Western blot, and methyl-DNA assays. We report that cortical thickness, neuroepithelial proliferation, and neuronal migration and maturity were found to be deterred by alcohol at E17. Simultaneously, DNA methylation, including 5-methylcytosine (5mC) and 5-hydroxcylmethylcytosine (5hmC), which progresses as an intrinsic program guiding normal embryonic cortical development, was severely affected by in utero alcohol exposure. The intricate relationship between cortical thinning and this DNA methylation program disruption is detailed and illustrated. DNA methylation, dynamic across the multiple cortical layers during the late embryonic stage, is highly disrupted by fetal alcohol exposure; this disruption occurs in tandem with characteristic developmental abnormalities, ranging from structural to molecular. Finally, our findings point to a significant question for future exploration: whether epigenetics guides neurodevelopment or whether developmental conditions dictate epigenetic dynamics in the context of alcohol-induced cortical teratogenesis.

Neurotrophins in the Brain: Interaction With Alcohol Exposure During Development

Fetal alcohol spectrum disorders (FASDs) are a result of the teratogenic effects of alcohol on the developing fetus. Decades of research examining both individuals with FASDs and animal models of developmental alcohol exposure have revealed the devastating effects of alcohol on brain structure, function, behavior, and cognition. Neurotrophic factors have an important role in guiding normal brain development and cellular plasticity in the adult brain. This chapter reviews the current literature showing that alcohol exposure during the developmental period impacts neurotrophin production and proposes avenues through which alcohol exposure and neurotrophin action might interact. These areas of overlap include formation of long-term potentiation, oxidative stress processes, neuroinflammation, apoptosis and cell loss, hippocampal adult neurogenesis, dendritic morphology and spine density, vasculogenesis and angiogenesis, and behaviors related to spatial memory, anxiety, and depression. Finally, we discuss how neurotrophins have the potential to act in a compensatory manner as neuroprotective molecules that can combat the deleterious effects of in utero alcohol exposure.

Behavioral deficits induced by third-trimester equivalent alcohol exposure in male C57BL/6J mice are not associated with reduced adult hippocampal neurogenesis but are still rescued with voluntary exercise

Prenatal alcohol exposure can produce permanent alterations in brain structure and profound behavioral deficits. Mouse models can help discover mechanisms and identify potentially useful interventions. This study examined long-term influences of either a single or repeated alcohol exposure during the third-trimester equivalent on survival of new neurons in the hippocampus, behavioral performance on the Passive avoidance and Rotarod tasks, and the potential role of exercise as a therapeutic intervention. C57BL/6J male mice received either saline or 5g/kg ethanol split into two s.c. injections, two hours apart, on postnatal day (PD)7 (Experiment 1) or on PD5, 7 and 9 (Experiment 2). All mice were weaned on PD21 and received either a running wheel or remained sedentary from PD35-PD80/81. From PD36-45, mice received i.p. injections of 50mg/kg bromodeoxyuridine (BrdU) to label dividing cells. Behavioral testing occurred between PD72-79. Number of surviving BrdU+ cells and immature neurons (doublecortin; DCX+) was measured at PD80-81. Alcohol did not affect number of BrdU+ or DCX+ cells in either experiment. Running significantly increased number of BrdU+ and DCX+ cells in both treatment groups. Alcohol-induced deficits on Rotarod performance and acquisition of the Passive avoidance task (Day 1) were evident only in Experiment 2 and running rescued these deficits. These data suggest neonatal alcohol exposure does not result in long-term impairments in adult hippocampal neurogenesis in the mouse model. Three doses of ethanol were necessary to induce behavioral deficits. Finally, the mechanisms by which exercise ameliorated the neonatal alcohol induced behavioral deficits remain unknown.

Selective reduction of cerebral cortex GABA neurons in a late gestation model of fetal alcohol spectrum disorder

Fetal alcohol spectrum disorders (FASD) are associated with cognitive and behavioral deficits, and decreased volume of the whole brain and cerebral cortex. Rodent models have shown that early postnatal treatments, which mimic ethanol toxicity in the third trimester of human pregnancy, acutely induce widespread apoptotic neuronal degeneration and permanent behavioral deficits. However, the lasting cellular and anatomical effects of early ethanol treatments are still incompletely understood. This study examined changes in neocortex volume, thickness, and cellular organization that persist in adult mice after postnatal day 7 (P7) ethanol treatment. Post mortem brain volumes, measured by both MRI within the skull and by fluid displacement of isolated brains, were reduced 10-13% by ethanol treatment. The cerebral cortex showed a similar reduction (12%) caused mainly by lower surface area (9%). In spite of these large changes, several features of cortical organization showed little evidence of change, including cortical thickness, overall neuron size, and laminar organization. Estimates of total neuron number showed a trend level reduction of about 8%, due mainly to reduced cortical volume but unchanged neuron density. However, counts of calretinin (CR) and parvalbumin (PV) subtypes of GABAergic neurons showed a striking >30% reduction of neuron number. Similar ethanol effects were found in male and female mice, and in C57BL/6By and BALB/cJ mouse strains. Our findings indicate that the cortex has substantial capacity to develop normal cytoarchitectonic organization after early postnatal ethanol toxicity, but there is a selective and persistent reduction of GABA cells that may contribute to the lasting cognitive and behavioral deficits in FASD.

Voluntary exercise partially reverses neonatal alcohol-induced deficits in mPFC layer II/III dendritic morphology of male adolescent rats

Developmental alcohol exposure in humans can produce a wide range of deficits collectively referred to as fetal alcohol spectrum disorders (FASD). FASD-related impairments in executive functioning later in life suggest long-term damage to the prefrontal cortex (PFC). In rodent neonates, moderate to high levels of alcohol exposure decreased frontal lobe brain size and altered medial PFC pyramidal neuron dendritic morphology. Previous research in our lab demonstrated that neonatal alcohol exposure decreased basilar dendritic complexity but did not affect spine density in Layer II/III pyramidal neurons in 26- to 30-day-old rats. The current study adds to the literature by evaluating the effect of neonatal alcohol exposure on mPFC Layer II/III basilar dendritic morphology in adolescent male rats. Additionally, it examines the potential for voluntary exercise to mitigate alcohol-induced deficits on mPFC dendritic complexity. An animal model of binge drinking during the third trimester of pregnancy was used. Rats were intubated with alcohol (alcohol-exposed, AE; 5.25 g kg(-1) day(-1)) on postnatal days (PD) 4-9; two control groups were included (suckle control and sham-intubated). Rats were anesthetized and perfused with heparinized saline solution on PD 42, and brains were processed for Golgi-Cox staining. Developmental alcohol exposure decreased spine density and dendritic complexity of basilar dendrites of Layer II/III neurons in the medial PFC (mPFC) compared to dendrites of control animals. Voluntary exercise increased spine density and dendritic length in AE animals resulting in elimination of the differences between AE and SH rats. Thus, voluntary exercise during early adolescence selectively rescued alcohol-induced morphological deficits in the mPFC.

Moderate prenatal alcohol exposure enhances GluN2B containing NMDA receptor binding and ifenprodil sensitivity in rat agranular insular cortex

Prenatal exposure to alcohol affects the expression and function of glutamatergic neurotransmitter receptors in diverse brain regions. The present study was undertaken to fill a current gap in knowledge regarding the regional specificity of ethanol-related alterations in glutamatergic receptors in the frontal cortex. We quantified subregional expression and function of glutamatergic neurotransmitter receptors (AMPARs, NMDARs, GluN2B-containing NMDARs, mGluR1s, and mGluR5s) by radioligand binding in the agranular insular cortex (AID), lateral orbital area (LO), prelimbic cortex (PrL) and primary motor cortex (M1) of adult rats exposed to moderate levels of ethanol during prenatal development. Increased expression of GluN2B-containing NMDARs was observed in AID of ethanol-exposed rats compared to modest reductions in other regions. We subsequently performed slice electrophysiology measurements in a whole-cell patch-clamp preparation to quantify the sensitivity of evoked NMDAR-mediated excitatory postsynaptic currents (EPSCs) in layer II/III pyramidal neurons of AID to the GluN2B negative allosteric modulator ifenprodil. Consistent with increased GluN2B expression, ifenprodil caused a greater reduction in NMDAR-mediated EPSCs from prenatal alcohol-exposed rats than saccharin-exposed control animals. No alterations in AMPAR-mediated EPSCs or the ratio of AMPARs/NMDARs were observed. Together, these data indicate that moderate prenatal alcohol exposure has a significant and lasting impact on GluN2B-containing receptors in AID, which could help to explain ethanol-related alterations in learning and behaviors that depend on this region.

Effects of ethanol exposure and withdrawal on dendritic morphology and spine density in the nucleus accumbens core and shell

Exposure to drugs of abuse can result in profound structural modifications on neurons in circuits involved in addiction that may contribute to drug dependence, withdrawal and related processes. Structural alterations on medium spiny neurons (MSNs) of the nucleus accumbens (NAc) have been observed following exposure to and withdrawal from a variety of drugs; however, relatively little is known about the effects of alcohol exposure and withdrawal on structural alterations of NAc MSNs. In the present study male rats were chronically exposed to vaporized ethanol for 10 days and underwent 1 or 7 days of withdrawal after which the brains were processed for Golgi-Cox staining and analysis of dendritic length, branching and spine density. MSNs of the NAc shell and core underwent different patterns of changes following ethanol exposure and withdrawal. At 1 day of withdrawal there were modest reductions in the dendritic length and branching of MSNs in both the core and the shell compared to control animals exposed only to air. At 7 days of withdrawal the length and branching of shell MSNs was reduced, whereas the length and branching of core MSNs were increased relative to the shell. The density of mature spines was increased in the core at 1 day of withdrawal, whereas the density of less mature spines was increased in both regions at 7 days of withdrawal. Collectively, these observations indicate that MSNs of the NAc core and shell undergo distinct patterns of structural modifications following ethanol exposure and withdrawal suggesting that modifications in dendritic structure in these regions may contribute differentially to ethanol withdrawal.

Brain development, experience, and behavior

Brain development progresses through a series of stages beginning with neurogenesis and progressing to neural migration, maturation, synaptogenesis, pruning, and myelin formation. This review examines the literature on how early experiences alter brain development, including environmental events such as sensory stimuli, early stress, psychoactive drugs, parent-child relationships, peer relationships, intestinal flora, diet, and radiation. This sensitivity of the brain to early experiences has important implications for understanding neurodevelopmental disorders as well as the effect of medical interventions in children.

Activity and social behavior in a complex environment in rats neonatally exposed to alcohol

Environmental complexity (EC) is a powerful, stimulating paradigm that engages animals through a variety of sensory and motor pathways. Exposure to EC (30 days) following 12 days of wheel running preserves hippocampal neuroplasticity in male rats neonatally exposed to alcohol during the third-trimester equivalent (binge-like exposure on postnatal days [PD] 4-9). The current experiment investigates the importance of various components of EC (physical activity, exploration, social interaction, novelty) and examines whether neonatal alcohol exposure affects how male rats interact with their environment and other male rats. Male pups were assigned to 1 of 3 neonatal conditions from PD 4-9: suckle control (SC), sham-intubated (SI), or alcohol-exposed (AE, 5.25 g/kg/day). From PD 30-42 animals were housed with 24-h access to a voluntary running wheel. The animals were then placed in EC from PD 42-72 (9 animals/cage, counterbalanced by neonatal condition). During EC, the animals were filmed for five 30-min sessions (PD 42, 48, 56, 64, 68). For the first experiment, the videos were coded for distance traveled in the cage, overall locomotor activity, time spent near other animals, and interaction with toys. For the second experiment, the videos were analyzed for wrestling, mounting, boxing, grooming, sniffing, and crawling over/under. AE animals were found to be less active and exploratory and engaged in fewer mounting behaviors compared to control animals. Results suggest that after exposure to wheel running, AE animals still have deficits in activity and social behaviors while housed in EC compared to control animals with the same experience.

Postnatal ethanol exposure simplifies the dendritic morphology of medium spiny neurons independently of adenylyl cyclase 1 and 8 activity in mice

BACKGROUND

Fetal exposure to alcohol can have multiple deleterious effects, including learning disorders and behavioral and executive functioning abnormalities, collectively termed fetal alcohol spectrum disorders. Neonatal mice lacking both calcium-/calmodulin-stimulated adenylyl cyclases (ACs) 1 and 8 demonstrate increased vulnerability to ethanol (EtOH)-induced neurotoxicity in the striatum compared with wild-type (WT) controls. However, the developmental impact on surviving neurons is still unclear.

METHODS

WT and AC1/8 double knockout (DKO) mice were administered 1 dose of EtOH (2.5 g/kg) between postnatal days 5 to 7 (P5-7). At P30, brains were removed and processed for Golgi-Cox staining. Medium spiny neurons (MSNs) from the caudate putamen were analyzed for changes in dendritic complexity; number of branches, branch points and terminals, total and average dendritic length; spine density and soma size.

RESULTS

EtOH significantly reduced the dendritic complexity and soma size in surviving MSNs regardless of genotype without affecting spine density. In the absence of EtOH, genetic deletion of AC1/8 reduced the dendritic complexity, number of branch points, spine density, and soma size of MSNs compared with WT controls.

CONCLUSIONS

These data indicate that neonatal exposure to a single dose of EtOH is sufficient to cause long-term alterations in the dendritic complexity of MSNs and that this outcome is not altered by the functional status of AC1 and AC8. Therefore, although deletion of AC1/8 demonstrates a role for the ACs in normal morphologic development and EtOH-induced neurodegeneration, loss of AC1/8 activity does not exacerbate the effects of EtOH on dendritic morphology or spine density.

Differential striatal spine pathology in Parkinson's disease and cocaine addiction: a key role of dopamine?

In the striatum, the dendritic tree of the two main populations of projection neurons, called "medium spiny neurons (MSNs)", are covered with spines that receive glutamatergic inputs from the cerebral cortex and thalamus. In Parkinson's disease (PD), striatal MSNs undergo an important loss of dendritic spines, whereas aberrant overgrowth of striatal spines occurs following chronic cocaine exposure. This review examines the possibility that opposite dopamine dysregulation is one of the key factors that underlies these structural changes. In PD, nigrostriatal dopamine degeneration results in a significant loss of dendritic spines in the dorsal striatum, while rodents chronically exposed to cocaine and other psychostimulants, display an increase in the density of "thin and immature" spines in the nucleus accumbens (NAc). In rodent models of PD, there is evidence that D2 dopamine receptor-containing MSNs are preferentially affected, while D1-positive cells are the main targets of increased spine density in models of addiction. However, such specificity remains to be established in primates. Although the link between the extent of striatal spine changes and the behavioral deficits associated with these disorders remains controversial, there is unequivocal evidence that glutamatergic synaptic transmission is significantly altered in both diseased conditions. Recent studies have suggested that opposite calcium-mediated regulation of the transcription factor myocyte enhancer factor 2 (MEF2) function induces these structural defects. In conclusion, there is strong evidence that dopamine is a major, but not the sole, regulator of striatal spine pathology in PD and addiction to psychostimulants. Further studies of the role of glutamate and other genes associated with spine plasticity in mediating these effects are warranted.

The atypical dopamine transport inhibitor, JHW 007, prevents amphetamine-induced sensitization and synaptic reorganization within the nucleus accumbens

Benztropine (BZT) analogs, a family of agents with high affinity for the dopamine transporter have been postulated as potential treatments in stimulant abuse due to their ability to attenuate a wide range of effects evoked by psychomotor stimulants such as cocaine and amphetamine (AMPH). Repeating administration of drugs, including stimulants, can result in behavioral sensitization, a progressive increase in their psychomotor activating effects. We examined in mice the sensitizing effects and the neuroplasticity changes elicited by chronic AMPH exposure, and the modulation of these effects by the BZT derivative and atypical dopamine uptake inhibitor, JHW007, a candidate medication for stimulant abuse. The results indicated that JHW007 did not produce sensitized locomotor activity when given alone but prevented the sensitized motor behavior induced by chronic AMPH administration. Morphological analysis of medium spiny neurons of the nucleus accumbens revealed that JHW 007 prevented the neuroadaptations induced by chronic AMPH exposure, including increments in dendritic arborization, lengthening of dendritic processes and increases in spine density. Furthermore, data revealed that AMPH produced an increase in the density of asymmetric, possibly glutamatergic synapses in the nucleus accumbens, an effect that was also blocked by JHW007 pretreatment. The present observations demonstrate that JHW007 is able to prevent not only AMPH-induced behavioral sensitization but also the long-term structural changes induced by chronic AMPH in the nucleus accumbens. Such findings support the development and evaluation of BZT derivatives as possible leads for treatment in stimulant addiction.

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.

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

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

Stress-induced grey matter loss determined by MRI is primarily due to loss of dendrites and their synapses

Stress, unaccompanied by signs of post-traumatic stress disorder, is known to decrease grey matter volume (GMV) in the anterior cingulate cortex (ACC) and hippocampus but not the amygdala in humans. We sought to determine if this was the case in stressed mice using high-resolution magnetic resonance imaging (MRI) and to identify the cellular constituents of the grey matter that quantitatively give rise to such changes. Stressed mice showed grey matter losses of 10 and 15 % in the ACC and hippocampus, respectively but not in the amygdala or the retrosplenial granular area (RSG). Concurrently, no changes in the number or volumes of the somas of neurons, astrocytes or oligodendrocytes were detected. A loss of synaptic spine density of up to 60 % occurred on different-order dendrites in the ACC and hippocampus (CA1) but not in the amygdala or RSG. The loss of spines was accompanied by decreases in cumulative dendritic length of neurons of over 40 % in the ACC and hippocampus (CA1) giving rise to decreases in volume of dendrites of 2.6 mm(3) for the former and 0.6 mm(3) for the latter, with no change in the amygdala or RSG. These values are similar to the MRI-determined loss of GMV following stress of 3.0 and 0.8 mm(3) in ACC and hippocampus, respectively, with no changes in the amygdala or RSG. This quantitative study is the first to relate GMV changes in the cortex measured with MRI to volume changes in cellular constituents of the grey matter.

Ethanol-induced disruption of Golgi apparatus morphology, primary neurite number and cellular orientation in developing cortical neurons

Prenatal ethanol exposure disrupts cortical neurite initiation and outgrowth, but prior studies have reported both ethanol-dependent growth promotion and inhibition. To resolve this ambiguity and better approximate in vivo conditions, we quantitatively analyzed neuronal morphology using a new, whole hemisphere explant model. In this model, Layer 6 (L6) cortical neurons migrate, laminate and extend neurites in an organotypic fashion. To selectively label L6 neurons, we performed ex utero electroporation of a GFP expression construct at embryonic day 13 and allowed the explants to develop for 2 days in vitro. Explants were exposed to (400 mg/dL) ethanol for either 4 or 24 h prior to fixation. Complete 3-D reconstructions were made of >80 GFP-positive neurons in each experimental condition. Acute responses to ethanol exposure included compaction of the Golgi apparatus accompanied by elaboration of supernumerary primary apical neurites, as well as a modest (∼15%) increase in higher order apical neurite length. With longer exposure time, ethanol exposure leads to a consistent, significant disorientation of the cell (cell body, primary apical neurite, and Golgi) with respect to the pial surface. The effects on cellular orientation were accompanied by decreased expression of cytoskeletal elements, microtubule-associated protein 2 and F-actin. These findings indicate that upon exposure to ethanol, developing L6 neurons manifest disruptions in Golgi apparatus and cytoskeletal elements which may in turn trigger selective and significant perturbations to primary neurite formation and neuronal polarity.

Experience and the developing prefrontal cortex

The prefrontal cortex (PFC) receives input from all other cortical regions and functions to plan and direct motor, cognitive, affective, and social behavior across time. It has a prolonged development, which allows the acquisition of complex cognitive abilities through experience but makes it susceptible to factors that can lead to abnormal functioning, which is often manifested in neuropsychiatric disorders. When the PFC is exposed to different environmental events during development, such as sensory stimuli, stress, drugs, hormones, and social experiences (including both parental and peer interactions), the developing PFC may develop in different ways. The goal of the current review is to illustrate how the circuitry of the developing PFC can be sculpted by a wide range of pre- and postnatal factors. We begin with an overview of prefrontal functioning and development, and we conclude with a consideration of how early experiences influence prefrontal development and behavior.

Prenatal ethanol exposure stimulates neurogenesis in hypothalamic and limbic peptide systems: possible mechanism for offspring ethanol overconsumption

Exposure to ethanol during the prenatal period contributes to increased alcohol consumption and preference in rodents and increased risk for alcoholism in humans. With studies in adult animals showing the orexigenic peptides, enkephalin (ENK), galanin (GAL) and orexin (OX), to stimulate ethanol consumption, the question addressed here is whether prenatal ethanol alters the development in utero of specific neurons that express these peptides. With reports describing suppressive effects of high doses of ethanol, we examined the offspring of dams gavaged from embryonic day 9 to parturition with a control solution or lower ethanol doses, 1 and 3g/kg/day, known to promote ethanol consumption in the offspring. To understand underlying mechanisms, measurements were taken in postnatal offspring of the expression of ENK in the hypothalamic paraventricular nucleus (PVN) and nucleus accumbens (NAc), GAL in the PVN, and OX in the perifornical lateral hypothalamus (PFLH) using real-time qPCR and in situ hybridization, and also of the cell proliferation marker, 5-bromo-2-deoxyuridine (BrdU), and its double-labeling with either neuronal nuclei (NeuN), a marker of mature neurons, or the peptides. On postnatal day 15 (P15), after two weeks without ethanol, the offspring showed increased expression of ENK in the PVN and NAc core but not shell, GAL in the PVN, and OX in the PFLH. In these same areas, prenatal ethanol compared to control increased the density at birth (P0) of neurons expressing these peptides and at P0 and P15 of neurons double-labeling BrdU and NeuN, indicating increased neurogenesis. These BrdU-positive neurons were found to express ENK, GAL and OX, indicating that prenatal ethanol promotes neurogenesis in these specific peptide systems. There were no changes in gliogenesis or apoptosis. This increase in neurogenesis and density of peptide-expressing neurons suggests the involvement of these hypothalamic and accumbal peptide systems in mediating the increased alcohol consumption observed in prenatal ethanol-exposed offspring.