Fetal alcohol exposure alters serotonin transporter sites in rat brain

Gestational Factors throughout Fetal Neurodevelopment: The Serotonin Link

Serotonin (5-HT) is a critical player in brain development and neuropsychiatric disorders. Fetal 5-HT levels can be influenced by several gestational factors, such as maternal genotype, diet, stress, medication, and immune activation. In this review, addressing both human and animal studies, we discuss how these gestational factors affect placental and fetal brain 5-HT levels, leading to changes in brain structure and function and behavior. We conclude that gestational factors are able to interact and thereby amplify or counteract each other's impact on the fetal 5-HT-ergic system. We, therefore, argue that beyond the understanding of how single gestational factors affect 5-HT-ergic brain development and behavior in offspring, it is critical to elucidate the consequences of interacting factors. Moreover, we describe how each gestational factor is able to alter the 5-HT-ergic influence on the thalamocortical- and prefrontal-limbic circuitry and the hypothalamo-pituitary-adrenocortical-axis. These alterations have been associated with risks to develop attention deficit hyperactivity disorder, autism spectrum disorders, depression, and/or anxiety. Consequently, the manipulation of gestational factors may be used to combat pregnancy-related risks for neuropsychiatric disorders.

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.

Prenatal alcohol exposure reduces 5-HT concentration in mouse intestinal muscle and mucosa

The influence of prenatal alcohol exposure on the serotoninergic system in the brain has been well studied, however its influence on the serotoninergic system in the gastrointestinal system remains unknown. The objective of the study was to use a mouse model of prenatal alcohol exposure to investigate the effects on serotonin and its metabolites and precursors in colonic tissue. This study used treatment of mouse breeding harems with 5% ethanol with saccharin via drinking water throughout pregnancy and compared the results with a saccharin control group. Tryptophan, serotonin (5-HT) and 5- hydroxyindoleacetic acid (5-HIAA) concentrations were measured in the longitudinal muscle myenteric plexus (LMMP) and mucosa of intestinal tissue by high-performance liquid chromatography (HPLC). Decreased 5-HT concentrations in mucosa and LMMP (females only) were observed in prenatally exposed mice compared to controls. Increases in mucosal and LMMP tryptophan concentration were only observed in prenatally exposed female mice. In conclusion, prenatal alcohol exposure causes a decrease in conversion of tryptophan to 5-HT in both muscle and mucosa although the effect is more pronounced in females. The observed sex difference may be related to changes associated with the estrous cycle.

An Update on Fetal Alcohol Syndrome-Pathogenesis, Risks, and Treatment

Alcohol is a well-established teratogen that can cause variable physical and behavioral effects on the fetus. The most severe condition in this spectrum of diseases is known as fetal alcohol syndrome (FAS). The differences in maternal and fetal enzymes, in terms of abundance and efficiency, in addition to reduced elimination, allow for alcohol to have a prolonged effect on the fetus. This can act as a teratogen through numerous methods including reactive oxygen species (generated as by products of CYP2E1), decreased endogenous antioxidant levels, mitochondrial damage, lipid peroxidation, disrupted neuronal cell-cell adhesion, placental vasoconstriction, and inhibition of cofactors required for fetal growth and development. More recently, alcohol has also been shown to have epigenetic effects. Increased fetal exposure to alcohol and sustained alcohol intake during any trimester of pregnancy is associated with an increased risk of FAS. Other risk factors include genetic influences, maternal characteristics, for example, lower socioeconomic statuses and smoking, and paternal chronic alcohol use. The treatment options for FAS have recently started to be explored although none are currently approved clinically. These include prenatal antioxidant administration food supplements, folic acid, choline, neuroactive peptides, and neurotrophic growth factors. Tackling the wider impacts of FAS, such as comorbidities, and the family system have been shown to improve the quality of life of FAS patients. This review aimed to focus on the pathogenesis, especially mechanisms of alcohol teratogenicity, and risks of developing FAS. Recent developments in potential management strategies, including prenatal interventions, are discussed.

Serotonergic Neuroplasticity in Alcohol Addiction

Alcohol addiction is a debilitating disorder producing maladaptive changes in the brain, leading drinkers to become more sensitive to stress and anxiety. These changes are key factors contributing to alcohol craving and maintaining a persistent vulnerability to relapse.

Serotonin (5-Hydroxytryptamine, 5-HT) is a monoamine neurotransmitter widely expressed in the central nervous system where it plays an important role in the regulation of mood. The serotonin system has been extensively implicated in the regulation of stress and anxiety, as well as the reinforcing properties of all of the major classes of drugs of abuse, including alcohol. Dysregulation within the 5-HT system has been postulated to underlie the negative mood states associated with alcohol use disorders.

This review will describe the serotonergic (5-HTergic) neuroplastic changes observed in animal models throughout the alcohol addiction cycle, from prenatal to adulthood exposure. The first section will focus on alcohol-induced 5-HTergic neuroadaptations in offspring prenatally exposed to alcohol and the consequences on the regulation of stress/anxiety. The second section will compare alterations in 5-HT signalling induced by acute or chronic alcohol exposure during adulthood and following alcohol withdrawal, highlighting the impact on the regulation of stress/anxiety signalling pathways. The third section will outline 5-HTergic neuroadaptations observed in various genetically-selected ethanol preferring rat lines. Finally, we will discuss the pharmacological manipulation of the 5-HTergic system on ethanol- and anxiety/stress-related behaviours demonstrated by clinical trials, with an emphasis on current and potential treatments.

Prenatal alcohol exposure alters methyl metabolism and programs serotonin transporter and glucocorticoid receptor expression in brain

Prenatal alcohol exposure (PAE) programs the fetal hypothalamic-pituitary-adrenal (HPA) axis, resulting in HPA dysregulation and hyperresponsiveness to stressors in adulthood. Molecular mechanisms mediating these alterations are not fully understood. Disturbances in one-carbon metabolism, a source of methyl donors for epigenetic processes, contributes to alcoholic liver disease. We assessed whether PAE affects one-carbon metabolism (including Mtr, Mat2a, Mthfr, and Cbs mRNA) and programming of HPA function genes (Nr3c1, Nr3c2, and Slc6a4) in offspring from ethanol-fed (E), pair-fed (PF), and ad libitum-fed control (C) dams. At gestation day 21, plasma total homocysteine and methionine concentrations were higher in E compared with C dams, and E fetuses had higher plasma methionine concentrations and lower whole brain Mtr and Mat2a mRNA compared with C fetuses. In adulthood (55 days), hippocampal Mtr and Cbs mRNA was lower in E compared with C males, whereas Mtr, Mat2a, Mthfr, and Cbs mRNA were higher in E compared with C females. We found lower Nr3c1 mRNA and lower nerve growth factor inducible protein A (NGFI-A) protein in the hippocampus of E compared with PF females, whereas hippocampal Slc6a4 mRNA was higher in E than C males. By contrast, hypothalamic Slc6a4 mRNA was lower in E males and females compared with C offspring. This was accompanied by higher hypothalamic Slc6a4 mean promoter methylation in E compared with PF females. These findings demonstrate that PAE is associated with alterations in one-carbon metabolism and has long-term and region-specific effects on gene expression in the brain. These findings advance our understanding of mechanisms of HPA dysregulation associated with PAE.

The utility of zebrafish to study the mechanisms by which ethanol affects social behavior and anxiety during early brain development

Exposure to moderate levels of ethanol during brain development has a number of effects on social behavior but the molecular mechanisms that mediate this are not well understood. Gaining a better understanding of these factors may help to develop therapeutic interventions in the future. Zebrafish offer a potentially useful model in this regard. Here, we introduce a zebrafish model of moderate prenatal ethanol exposure. Embryos were exposed to 20mM ethanol for seven days (48hpf-9dpf) and tested as adults for individual social behavior and shoaling. We also tested their basal anxiety with the novel tank diving test. We found that the ethanol-exposed fish displayed reductions in social approach and shoaling, and an increase in anxiety in the novel tank test. These behavioral differences corresponded to differences in hrt1aa, slc6a4 and oxtr expression. Namely, acute ethanol caused a spike in oxtr and ht1aa mRNA expression, which was followed by down-regulation at 7dpf, and an up-regulation in slc6a4 at 72hpf. This study confirms the utility of zebrafish as a model system for studying the molecular basis of developmental ethanol exposure. Furthermore, it proposes a putative developmental mechanism characterized by ethanol-induced OT inhibition leading to suppression of 5-HT and up-regulation of 5-HT1A, which leads, in turn, to possible homeostatic up-regulation of 5-HTT at 72hpf and subsequent imbalance of the 5-HT system.

Neurotrophic peptides, ADNF-9 and NAP, prevent alcohol-induced apoptosis at midgestation in fetal brains of C57BL/6 mouse

Prenatal alcohol exposure is known to induce fetal brain growth deficits at different embryonic stages. We focused this study on investigating the neuroprotective effects against alcohol-induced apoptosis at midgestation using activity-dependent neurotrophic factor (ADNF)-9, a peptide (SALLRSIPA) derived from activity-dependent neurotrophic factor, and NAP, a peptide (NAPVSIPQ) derived from activity-dependent neuroprotective protein. We used an established fetal alcohol exposure mouse model. On embryonic day 7 (E7), weight-matched pregnant females were assigned to the following groups: (1) ethanol liquid diet (ALC) group with 25 % (4.49 %, v/v) ethanol-derived calories, (2) pair-fed (PF) control group, (3) ALC combined with i.p. injections (1.5 mg/kg) of ADNF-9 (ALC/ADNF-9) group, (4) ALC combined with i.p. injections (1.5 mg/kg) of NAP (ALC/NAP) group, (5) PF liquid diet combined with i.p. injections of ADNF-9 (PF/ADNF-9) group, and (6) PF liquid diet combined with i.p. injections of NAP (PF/NAP) group. On day 15 (E15), fetal brains were collected, weighed, and assayed for TdT-mediated dUTP nick end labeling (TUNEL) staining. ADNF-9 or NAP was administered daily from E7 to E15 alongside PF or ALC liquid diet exposure. Our results show that NAP and ADNF-9 significantly prevented alcohol-induced weight reduction of fetal brains. Apoptosis was determined by TUNEL staining; NAP or ADNF-9 administration alongside alcohol exposure significantly prevented alcohol-induced increase in TUNEL-positive cells in primordium of the cingulate cortex and ganglionic eminence. These findings may pave the path toward potential therapeutics against alcohol intoxication during pregnancy stages.

The serotonergic anatomy of the developing human medulla oblongata: implications for pediatric disorders of homeostasis

The caudal serotonergic (5-HT) system is a critical component of a medullary "homeostatic network" that regulates protective responses to metabolic stressors such as hypoxia, hypercapnia, and hyperthermia. We define anatomically the caudal 5-HT system in the human medulla as 5-HT neuronal cell bodies located in the raphé (raphé obscurus, raphé magnus, and raphé pallidus), extra-raphé (gigantocellularis, paragigantocellularis lateralis, intermediate reticular zone, lateral reticular nucleus, and nucleus subtrigeminalis), and ventral surface (arcuate nucleus). These 5-HT neurons are adjacent to all of the respiratory- and autonomic-related nuclei in the medulla where they are positioned to modulate directly the responses of these effector nuclei. In the following review, we highlight the topography and development of the caudal 5-HT system in the human fetus and infant, and its inter-relationships with nicotinic, GABAergic, and cytokine receptors. We also summarize pediatric disorders in early life which we term "developmental serotonopathies" of the caudal (as well as rostral) 5-HT domain and which are associated with homeostatic imbalances. The delineation of the development and organization of the human caudal 5-HT system provides the critical foundation for the neuropathologic elucidation of its disorders directly in the human brain.

Extensive deep gray matter volume reductions in children and adolescents with fetal alcohol spectrum disorders

BACKGROUND

The link between the numerous cognitive, motor, and behavioral difficulties of individuals with fetal alcohol spectrum disorders (FASD) and underlying specific structural brain injuries can be investigated using high-resolution imaging. Differential sensitivity of the brain's "relay" stations, namely the deep gray matter structures, may play a key factor given their multifaceted role in brain function. The purpose of our study was to analyze differences in deep gray matter volumes of children and adolescents with FASD relative to age/sex-matched controls and to examine whether any volume differences were consistent across the age range of neurodevelopment.

METHODS

Children and adolescents (N = 28, 6 to 17 years) diagnosed with FASD and 56 age- and sex-matched healthy controls (i.e., 2 matched controls per FASD subject) underwent 3-dimensional T1-weighted MRI scans that were used for the automated volume measurement (FreeSurfer) of the intracranial space, total white matter, cortical gray matter, and 6 deep gray matter structures, namely the hippocampus, amygdala, thalamus, caudate, putamen, and globus pallidus, with left and right measured separately. Volumes were compared between FASD and controls, as well as changes with age.

RESULTS

Significant reductions of volume in FASD were observed for the intracranial vault (7.6%), total white matter (8.6%), total cortical gray matter (7.8%), and total deep gray matter (13.1%). All 6 deep gray matter structures showed significant volume reductions bilaterally with the caudate (approximately 16%) and globus pallidus (approximately 18%) being most affected. The hippocampus, thalamus, and globus pallidus showed reductions in all 3 age subgroups (6 to 9, 10 to 13, and 14 to 17 years) but the caudate and putamen had smaller volumes for FASD only within the 2 youngest subgroups; the amygdala was only smaller for FASD in the 2 oldest subgroups.

CONCLUSIONS

Significant, but variable, volume reductions throughout the deep gray matter are observed over a wide age range of 6 to 17 years in FASD.

Prenatal alcohol exposure: fetal programming and later life vulnerability to stress, depression and anxiety disorders

Children with fetal alcohol spectrum disorder (FASD) exhibit cognitive, neuropsychological and behavioral problems, and numerous secondary disabilities including depression and anxiety disorders. Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis is common in depression/anxiety, reflected primarily in increased HPA tone or activity. Prenatal alcohol exposure (PAE) increases HPA tone and results in HPA dysregulation throughout life, paralleling many of the HPA changes in depression/anxiety. We review data demonstrating altered HPA function and increased depression/anxiety in FASD. In the context of the stress-diathesis model, we discuss the hypothesis that fetal programming of the HPA axis by PAE alters neuroadaptive mechanisms that mediate the stress response, thus sensitizing the organism to stressors encountered later in life, and mediating, at least partly, the increased vulnerability to depression/anxiety disorders. Furthermore, we present evidence demonstrating sex-specific alterations in both hormonal and behavioral responsiveness to tasks measuring depressive- and anxiety-like behaviors in PAE offspring. Overall, the research suggests that the stress-diathesis model provides a powerful approach for elucidating mechanisms underlying the increased vulnerability to mental illness among individuals with FASD, and developing appropriate treatments for these individuals. Dr. Seymour Levine's seminal work on the long-term consequences of early life experiences formed a framework for the development of the research described in this review.

Prenatal alcohol exposure alters biobehavioral reactivity to pain in newborns

OBJECTIVES

To examine biobehavioral responses to an acute pain event in a Cape Town, South Africa, cohort consisting of 28 Cape Colored (mixed ancestry) newborns (n = 14) heavily exposed to alcohol during pregnancy (exposed), and born to abstainers (n = 14) or light (< or = 0.5 oz absolute alcohol/d) drinkers (controls).

METHODS

Mothers were recruited during the third trimester of pregnancy. Newborn data were collected on postpartum day 3 in the maternity obstetrical unit where the infant had been delivered. Heavy prenatal alcohol exposure was defined as maternal consumption of at least 14 drinks/wk or at least 1 incident of binge drinking/mo. Acute stress-related biobehavioral markers [salivary cortisol, heart rate (HR), respiratory sinus arrhythmia (RSA), spectral measures of heart rate variability (HRV), and videotaped facial actions] were collected thrice during a heel lance blood collection (baseline, lance, and recovery). After a feeding and nap, newborns were administered an abbreviated Brazelton Neonatal Behavioral Assessment Scale.

RESULTS

There were no between-group differences in maternal age, marital status, parity, gravidity, depression, anxiety, pregnancy smoking, maternal education, or infant gestational age at birth (all ps > 0.15). In both groups, HR increased with the heel lance and decreased during the postlance period. The alcohol-exposed group had lower mean HR than controls throughout, and showed no change in RSA over time. Cortisol levels showed no change over time in controls but decreased over time in exposed infants. Although facial action analyses revealed no group differences in response to the heel lance, behavioral responses assessed on the Brazelton Neonatal Scale showed less arousal in the exposed group.

CONCLUSIONS

Both cardiac autonomic and hypothalamic-pituitary-adrenal stress reactivity measures suggest a blunted response to an acute noxious event in alcohol-exposed newborns. This is supported by results on the Brazelton Neonatal Scale indicating reduced behavioral arousal in the exposed group. To our knowledge, these data provide the first biobehavioral examination of early pain reactivity in alcohol-exposed newborns and have important implications for understanding neuro-/biobehavioral effects of prenatal alcohol exposure in the newborn period.

Tolerance to ethanol sedation and withdrawal hyper-excitability is mediated via neuropeptide Y Y1 and Y5 receptors

AIMS

Neuropeptide Y (NPY) is widely distributed throughout the brain and has been implicated in some of the actions of ethanol. The aim of the present study was to characterize the subtypes of NPY receptors in ethanol induced sedation, tolerance and withdrawal hyper-excitability.

MAIN METHODS

The loss of righting reflex paradigm was used to record the sleep duration in mice.

KEY FINDINGS

The acute administration of ethanol (3-4g per kg, i.p., 20%v/v) resulted in marked sedation. While prolonged ethanol consumption led to the development of tolerance, the mice showed hyper-excitability following ethanol withdrawal. Prior acute intracerebroventricular (i.c.v.) injection of NPY (5-20 ng per mouse) or NPY Y1 and Y5 receptors agonist [Leu(31), Pro(34)]-NPY (0.02-0.2 ng per mouse) potentiated ethanol induced sedation. On the other hand, administration of selective NPY Y1 receptor antagonist BIBP3226 (5 ng per mouse, i.c.v.) inhibited ethanol induced sedation. Chronic concomitant treatment of NPY (20 ng per mouse, i.c.v.) or [Leu(31), Pro(34)]-NPY (0.2 ng per mouse, i.c.v.) to ethanol-fed groups prevented the development of tolerance and attenuated withdrawal hyper-excitability. Moreover, acute treatment of NPY (5 ng per mouse, i.c.v.) or [Leu(31), Pro(34)]-NPY (0.02 ng per mouse, i.c.v.) reversed the peak ethanol withdrawal hyper-excitability.

SIGNIFICANCE

The results underscore a role for NPY Y1 and Y5 receptors in the ethanol induced sedation, tolerance and withdrawal hyper-excitability. We suggest that modulation of NPY Y1 and Y5 receptors may be a strategy to address the ethanol withdrawal conditions.

Prenatal alcohol exposure: foetal programming, the hypothalamic-pituitary-adrenal axis and sex differences in outcome

Prenatal exposure to alcohol has adverse effects on offspring neuroendocrine and behavioural functions. Alcohol readily crosses the placenta, thus directly affecting developing foetal endocrine organs. In addition, alcohol-induced changes in maternal endocrine function can disrupt the normal hormonal interactions between the pregnant female and foetal systems, altering the normal hormone balance and, indirectly, affecting the development of foetal metabolic, physiological and endocrine functions. The present review focuses on the adverse effects of prenatal alcohol exposure on offspring neuroendocrine function, with particular emphasis on the hypothalamic-pituitary-adrenal (HPA) axis, a key player in the stress response. The HPA axis is highly susceptible to programming during foetal and neonatal development. Here, we review data demonstrating that alcohol exposure in utero programmes the foetal HPA axis such that HPA tone is increased throughout life. Importantly, we show that, although alterations in HPA responsiveness and regulation are robust phenomena, occurring in both male and female offspring, sexually dimorphic effects of alcohol are frequently observed. We present updated findings on possible mechanisms underlying differential effects of alcohol on male and female offspring, with special emphasis on effects at different levels of the HPA axis, and on modulatory influences of the hypothalamic-pituitary-gonadal hormones and serotonin. Finally, possible mechanisms underlying foetal programming of the HPA axis, and the long-term implications of increased exposure to endogenous glucocorticoids for offspring vulnerability to illnesses or disorders later in life are discussed.

Early adversity and alcohol availability persistently modify serotonin and hypothalamic–pituitary–adrenal-axis metabolism and related behavior: What experimental research on rodents and primates can tell us

Early experiences have profound influences on individual developmental trajectories. For example alcohol exposure during central nervous system development relates to a number of pathological consequences in adulthood. An increased risk of developing psychiatric disorders, like major depression and impulse-control-related pathologies is associated with alcohol exposure during fetal life and/or during adolescence. Additionally, adverse life experiences occurring early in development may exacerbate these consequences, while impinging on the same neural systems affected by precocious alcohol exposure. Conversely, a protective and/or stimulating environment may mitigate these alcohol-related negative outcomes. Experimental research in animal models constitutes a primary source of information in understanding both functional and dysfunctional human adaptations to these events. In this review, a selection of rodent and primate studies shows that developmental ethanol exposure on the one hand, and environmental treatments aimed at modifying the mother-offspring interaction on the other hand, independently modulate similar neuro-endocrine systems. In particular, we discuss the effects that the above-mentioned independent variables exert on the hypothalamic-pituitary-adrenal (HPA)-axis and on brain serotonergic pathways. Experimental evidence indicates that pathological adaptations of these systems are valuable predictors of human neuro-behavioral abnormalities like depression, impaired impulse control and alcohol abuse. Finally, a working hypothesis is proposed, which combines primate and rodent studies aimed: (i) at studying functional and pathological individual development following early ethanol consumption, and (ii) at heading towards a better definition of potential intervention strategies.

Fetal Alcohol Exposure Reduces Serotonin Innervation and Compromises Development of the Forebrain Along the Serotonergic Pathway

BACKGROUND

We reported previously that a moderate level of fetal alcohol treatment reduces the birth, maturation, and migration of serotonin (5-HT) neurons at embryonic days 11 to 15 (E11-E15). Because 5-HT is known as a differentiation signal for forebrain development, we investigated whether alcohol affects 5-HT innervation to the developing brain and how the target brain areas grow as they receive 5-HT innervation between E15 and E18.

METHODS

Pregnant dams were divided into three groups and treated from E7 to E15 or E18 with one of the following conditions: (1) liquid diet that contained 25% ethanol-derived calories (ALC), (2) isocaloric liquid diet pair-fed (PF), or (3) chow fed (Chow). The 5-HT immunostained (5-HT-IM) fibers and size of brain areas were examined as an index of growth along the ascending 5-HT pathway.

RESULT

We found that 5-HT-IM fibers innervate the brain regions specifically under active differentiation and that there were three sets of correlated dysmorphology in the ALC group as compared with those of the PF and Chow groups. The three sets are as follows: (1) fewer 5-HT-IM fibers in the medial forebrain bundle and along the projecting pathway through the hypothalamus, septal nucleus, frontal and parietal cortices, and subiculum/hippocampus; (2) underdevelopment of the brain regions along 5-HT fiber projections; and (3) underdevelopment of somatosensory thalamocortical projections, which are known to transiently express 5-HT transporters and to be regulated by 5-HT. No such differences were found between the PF and Chow groups.

CONCLUSION

We found that fewer 5-HT fibers grew in the embryos that were exposed to alcohol. As forebrain regions differentiated along the 5-HT projection, we found two reductions: (1) the growth of brain regions along 5-HT projection and (2) the growth of the thalamocortical sensory projection regulated by 5-HT. The reduced 5-HT innervation is in agreement with our previous observation of fewer 5-HT neurons. The subsequent retardation of forebrain growth and sensory thalamocortical fibers along the pathway of reduced 5-HT projection is consistent with the role of 5-HT as a signal for forebrain differentiation.

Prenatal Alcohol Exposure Causes Long-Term Serotonin Neuron Deficit in Mice

BACKGROUND

Previous work from this laboratory showed that prenatal alcohol exposure at approximately 100 mg/dl from embryonic day (E)7 to early midgestation reduced the number and retarded the migration of serotonin (5-HT) neurons in the raphe nuclei in C57BL/6 mice. In this study, we report that the deficit of 5-HT neurons found in midgestation persisted on E18 and into young adulthood.

METHODS

Pregnant dams were treated from E7 to E18 in three groups--(1) the alcohol group, fed with liquid diet with 25% ethanol-derived calories; (2) the isocaloric pair-fed group; and (3) the chow group for analysis of concentrations of active caspase-3--to study apoptosis at E18 in the brainstem and the number of 5-HT neurons at E18 and postnatal day 45. The concentrations of active caspase-3 were determined by using a colorimetric assay, and the 5-HT neurons were determined by immunocytochemistry.

RESULTS

Prenatal alcohol exposure increased the concentration of active caspase-3 in the brainstem and caused reductions in brain weight by 20% and in the total number of 5-HT-immunostaining neurons in the dorsal and median raphe nuclei by 20% at E18 as compared with those of the pair-fed and chow controls. Continuous observation from prenatal to postnatal stages showed that the reduction of 5-HT-immunostaining neurons in the dorsal and median raphe nuclei persisted in the young adult stage.

CONCLUSIONS

Upon prenatal alcohol exposure, an increased concentration of active caspase-3 and a decreased number of 5-HT-immunostaining neurons in the brainstem were observed at E18. The decreased number of 5-HT neurons persisted to the young adult stage of postnatal day 45. This suggests that ethanol has a long-lasting effect on 5-HT deficit. A fetal alcohol exposure-rendered lasting deficit of 5-HT and other transmitter systems may underlie the neuropsychiatric deficits in fetal alcohol spectrum disorder.

Deep serotonergic and dopaminergic structures in fetal alcoholic syndrome: a study with nor-beta-CIT-single-photon emission computed tomography and magnetic resonance imaging volumetry

BACKGROUND

In prenatally alcohol exposed children, the relationship between brain structure and function is highlighted to be important to study.

METHODS

We studied 12 children with fetal alcoholic syndrome (FAS) and fetal alcoholic effects (FAE) by magnetic resonance imaging volumetry and by single-photon emission computed tomography with iodine-123 labeled 2beta-carbomethoxy-3beta-(4-iodophenyl) ([123I]nor-beta-CIT) and related these findings to those from neuropsychological and psychiatric tests.

RESULTS

The absolute volumes of studied nuclei, including the brain volume, were significantly smaller in FAS/FAE children than in control patients. After normalization of volumes, significant differences were not found. Left hippocampus was smaller than the right (p<.003) but did not significantly differ from the control subjects. The children with FAS/FAE showed reduced serotonin (p=.02) in the medial frontal cortex and slightly increased striatal dopamine transporter binding. All FAS/FAE children had attention-deficit/hyperkinetic disorder (ADHD). None had depression. The internalization scores correlated with dopamine transporter binding (r=-.65; p=.03).

CONCLUSIONS

The results indicate that the serotonin (5-HT) system may be vulnerable to the effects of ethanol in utero. The high dopamine transporter levels may correlate with the ADHD findings. Reduced serotonin and increased binding of dopamine transporter are also seen in type 2 alcoholism. Some behavioral problems of FAS/FAE might be preventable by early intervention and treatment.

Effects of prenatal alcohol exposure on the development of the vibrissal somatosensory cortical barrel network

We have previously shown that the serotonin (5-HT) and its thalamocortical afferents are compromised by prenatal alcohol exposure (PAE). The development of the sensory cortical barrels is regulated by 5-HT-rich thalamocortical afferents. Therefore, it is hypothesized that PAE will deleteriously affect the postnatal development of the cortical barrel formations. On embryonic day (E)7, C57BL/6 mice were grouped into: Alcohol (Alc), Pair-fed (PF), or Chow, and maintained on diet until E18. On postnatal day 7, cortices were stained with 5-HT for thalamocortical fibers, and a NeuN for identification of mature neurons. The area of the posterior medial barrel subfield (PMBSF), was measured as well as the number of NeuN+ neurons within the barrel patches. Though brain weight and brain volume were similar among the three groups, a significant reduction was seen in total area of the PMBSF, and in the average individual barrel area in the Alc group as compared to Chow. Furthermore, the volumes of the B, but not C row barrels were significantly reduced. Barrels were found missing in layer IV, specifically in the posterior aspects of the A, B, and straddler row in the Alc group. Cell counts demonstrated a nearly 50% reduction in NeuN+ neuron number in both rows. This reduction in size of the PMBSF and fewer neurons within these sensory barreloids may underlie a change in the development of the discriminatory sensitivity of the whiskers and serves as an excellent model for the study of a compromised sensory modality following PAE.

Ethanol induces expression of the glutamate transporters EAAT1 and EAAT2 in organotypic cortical slice cultures

BACKGROUND

Exposure of the developing brain to ethanol disposes the fetus to fetal alcohol syndrome and causes a number of changes in several neurochemical systems. In particular, the glutamatergic system is affected by ethanol. Thus, increased sensitivity of glutamate receptors and enhanced transmembrane transport of glutamate were found in primary astrocyte cultures. However, in these in vitro studies, changes in the expression of glutamate transporters were not detected. To further characterize the influence of chronic ethanol exposure on the developing brain, we assessed the transcriptional and translational regulation of glutamate transporters in a less artificial in vitro system.

METHODS

We exposed postnatal rat cortical organotypic slice cultures to ethanol (100 mM) for 4 and 8 days. Expression of the excitatory amino acid transporters EAAT1 and EAAT2 was analyzed in comparison to untreated controls with semiquantitative reverse transcriptase-polymerase chain reaction. In addition, changes in protein expression were detected by Western blotting.

RESULTS

In ethanol-exposed cortical slices, we observed more prominent fiber outgrowth and significantly increased gene expression (EAAT1: +35%, p = 0.029; EAAT2: +251%, p = 0.015). These findings could be verified on the protein level, because Western blot analysis revealed significantly higher levels of EAAT1 (+76%; p = 0.008) and EAAT2 (+104%; p = 0.018) in ethanol-treated slices compared with controls.

CONCLUSIONS

Our results are in concert with earlier studies describing the induction of glutamate transport by ethanol. Enhanced expression of EAAT1 and EAAT2 after ethanol exposure can be viewed as a maladaptive process that disposes the developing brain to fetal alcohol syndrome.

Deviations in brain early serotonergic development as a result of fetal alcohol exposure

Serotonin (5-HT) has specific roles not only as a transmitter but also as a signal for differentiation. We recently found that alcohol drinking during pregnancy resulted in incomplete-neural-tube-fusion which hindered the development of midline cells such as 5-HT neurons in mice. We now report that, at the birth of 5-HT neurons (E11), the 5-HT immunoreative (5-HT-im) neurons are often found missing medial projecting fibers towards ventricle in the Alcohol treated group (ALC) as compared with pair-fed (PF) and Chow-fed groups (Chow) in mice. At E13, there are fewer 5-HT-im neurons in either dorsal or median raphe of ALC as compared with PF or Chow; furthermore, neurite outgrowth and migration of the 5-HT neurons are also compromised with alcohol exposure. We, thus, demonstrated that fetal alcohol exposure compromised 5-HT development as early as at the 5-HT neuron birth. Since 5-HT is a signal for development of many forebrain neurons, the deviation of 5-HT in early life may have consequences on brain development that extend beyond those seen in the 5-HT system.

Neurodevelopmental liabilities of substance abuse

The perinate is particularly risk-prone to chemical species which have the potential of inducing neuronal apoptosis or necrosis and thereby adversely altering development of the brain, to produce life-long functional and behavioral deficits. This paper is an overview for many substances of abuse, but the purview is much more broadened by the realization that even elevated levels of estrogens and corticosteroids in the pregnant mother can act as neuroteratogens, by passing via the placenta and altering neural development or inducing apoptosis in the perinate. Finally, therapeutic risks of anesthetics are highlighted, as these too induce neuronal apoptosis in the neonate by either blocking N-methyl-D-aspartate receptors or by acting as gamma-aminobutyric acid agonists. By understanding the mechanisms involved it may ultimately be possible to interrupt the mechanistic scheme and thereby prevent neuroteratological processes.

Alcohol deters the outgrowth of serotonergic neurons at midgestation

We have previously demonstrated that treatment of pregnant C57BL mice from gestation days 8 to 14 with alcohol with 20% ethanol-derived calories (EDC) reduced the number of serotonin (5-HT) neurons and retarded their migration in the fetal brains. In the present study, we obtained similar results with the use of 25% EDC and extended our previous findings by demonstrating that besides the alteration of the number of 5-HT neurons, prenatal alcohol exposure also affects their projecting fibers in their early development. Pregnant C57BL mice were divided into an alcohol-exposed (ALC) group given 25% EDC (4.49%, v/v), a pair-fed group to the ethanol-fed group (PF) and a chow-fed group (Chow). The PF and Chow groups served as controls. Our results showed that in the ALC group, when compared with the control groups, prenatal alcohol exposure with 25% EDC reduced the number of 5-HT-immunoreactive neurons in both the median and dorsal raphe, and the amount of 5-HT-immunoreactive fibers in the medial forebrain bundle (MFB). The diameter of the 5-HT-immunoreactive MFB was also reduced as a result of treatment. No significant differences of the above parameters were found between the PF and Chow groups. The previous and present work confirmed that alcohol reduces the normal formation and growth of 5-HT neurons in the midbrain. Furthermore, the projection of 5-HT fibers, in density as well as in distribution, is reduced in the major trajectory bundle. This may affect the amount of 5-HT fibers available to the forebrain. In light of the importance of the 5-HT system in brain development, alcohol may affect the growth of the forebrain through its effect on 5-HT signaling.