Hypothalamic-pituitary-adrenal axis and behavioral dysfunction following early binge-like prenatal alcohol exposure in mice.

The range of defects that fall within fetal alcohol spectrum disorder (FASD) includes persistent behavioral problems, with anxiety and depression being two of the more commonly reported issues. Previous studies of rodent FASD models suggest that interference with hypothalamic-pituitary-adrenal (HPA) axis structure and/or function may be the basis for some of the prenatal alcohol (ethanol) exposure (PAE)-induced behavioral abnormalities. Included among the previous investigations are those illustrating that maternal alcohol treatment limited to very early stages of pregnancy (i.e., gestational day [GD]7 in mice; equivalent to the third week post-fertilization in humans) can cause structural abnormalities in areas such as the hypothalamus, pituitary gland, and other forebrain regions integral to controlling stress and behavioral responses. The current investigation was designed to further examine the sequelae of prenatal alcohol insult at this early time period, with particular attention to HPA axis-associated functional changes in adult mice. The results of this study reveal that GD7 PAE in mice causes HPA axis dysfunction, with males and females showing elevated corticosterone (CORT) and adrenocorticotropic hormone (ACTH) levels, respectively, following a 15-min restraint stress exposure. Males also showed elevated CORT levels following an acute alcohol injection of 2.0 g/kg, while females displayed blunted ACTH levels. Furthermore, analysis showed that anxiety-like behavior was decreased after GD7 PAE in female mice, but was increased in male mice. Collectively, the results of this study show that early gestational alcohol exposure in mice alters long-term HPA axis activity and behavior in a sexually dimorphic manner.

Prenatal alcohol exposure reduces magnetic susceptibility contrast and anisotropy in the white matter of mouse brains.

Prenatal alcohol exposure can result in long-term cognitive and behavioral deficits. Fetal alcohol spectrum disorder (FASD) refers to a range of permanent birth defects caused by prenatal alcohol exposure, and is the most common neurodevelopmental disorder in the US. Studies by autopsy and conventional structural MRI indicate that the midline structures of the brain are particularly vulnerable to prenatal alcohol exposure. Diffusion tensor imaging (DTI) has shown that abnormalities in brain white matter especially the corpus callosum are very common in FASD. Quantitative susceptibility mapping (QSM) is a novel technique that measures tissue's magnetic property. Such magnetic property is affected by tissue microstructure and molecular composition including that of myelin in the white matter. In this work, we studied three major white matter fiber bundles of a mouse model of FASD and compared it to control mice using both QSM and DTI. QSM revealed clear and significant abnormalities in anterior commissure, corpus callosum, and hippocampal commissure, which were likely due to reduced myelination. Our data also suggested that QSM may be even more sensitive than DTI for examining changes due to prenatal alcohol exposure. Although this is a preclinical study, the technique of QSM is readily translatable to human brain.

Characterization of subtle brain abnormalities in a mouse model of Hedgehog pathway antagonist-induced cleft lip and palate.

Subtle behavioral and cognitive deficits have been documented in patient cohorts with orofacial clefts (OFCs). Recent neuroimaging studies argue that these traits are associated with structural brain abnormalities but have been limited to adolescent and adult populations where brain plasticity during infancy and childhood may be a confounding factor. Here, we employed high resolution magnetic resonance microscopy to examine primary brain morphology in a mouse model of OFCs. Transient in utero exposure to the Hedgehog (Hh) signaling pathway antagonist cyclopamine resulted in a spectrum of facial dysmorphology, including unilateral and bilateral cleft lip and palate, cleft of the secondary palate only, and a non-cleft phenotype marked by midfacial hypoplasia. Relative to controls, cyclopamine-exposed fetuses exhibited volumetric differences in several brain regions, including hypoplasia of the pituitary gland and olfactory bulbs, hyperplasia of the forebrain septal region, and expansion of the third ventricle. However, in affected fetuses the corpus callosum was intact and normal division of the forebrain was observed. This argues that temporally-specific Hh signaling perturbation can result in typical appearing OFCs in the absence of holoprosencephaly--a condition classically associated with Hh pathway inhibition and frequently co-occurring with OFCs. Supporting the premise that some forms of OFCs co-occur with subtle brain malformations, these results provide a possible ontological basis for traits identified in clinical populations. They also argue in favor of future investigations into genetic and/or environmental modulation of the Hh pathway in the etiopathogenesis of orofacial clefting.

Fully automated rodent brain MR image processing pipeline on a Midas server: from acquired images to region-based statistics.

Magnetic resonance imaging (MRI) of rodent brains enables study of the development and the integrity of the brain under certain conditions (alcohol, drugs etc.). However, these images are difficult to analyze for biomedical researchers with limited image processing experience. In this paper we present an image processing pipeline running on a Midas server, a web-based data storage system. It is composed of the following steps: rigid registration, skull-stripping, average computation, average parcellation, parcellation propagation to individual subjects, and computation of region-based statistics on each image. The pipeline is easy to configure and requires very little image processing knowledge. We present results obtained by processing a data set using this pipeline and demonstrate how this pipeline can be used to find differences between populations.

Magnetic resonance microscopy-based analyses of the neuroanatomical effects of gestational day 9 ethanol exposure in mice.

Animal model-based studies have shown that ethanol exposure during early gestation induces developmental stage-specific abnormalities of the face and brain. The exposure time-dependent variability in ethanol's teratogenic outcomes is expected to contribute significantly to the wide spectrum of effects observed in humans with fetal alcohol spectrum disorder (FASD). The work presented here employs a mouse FASD model and magnetic resonance microscopy (MRM; high resolution magnetic resonance imaging) in studies designed to further our understanding of the developmental stage-specific defects of the brain that are induced by ethanol. At neurulation stages, i.e. at the beginning of gestational day (GD) 9 and again 4 hours later, time-mated C57Bl/6J dams were intraperitoneally administered 2.9 g/kg ethanol or vehicle. Ethanol-exposed fetuses were collected on GD 17, processed for MRM analysis, and results compared to comparably staged controls. Linear and volume measurements as well as shape changes for numerous individual brain regions were determined. GD 9 ethanol exposure resulted in significantly increased septal region width, reduction of cerebellar volume, and enlargement of all of the ventricles. Additionally, the results of shape analyses showed that many areas of the ethanol-exposed brains including the cerebral cortex, hippocampus and right striatum were significantly misshapen. These data demonstrate that ethanol can induce dysmorphology that may not be obvious based on volumetric analyses alone, highlight the asymmetric aspects of ethanol-induced defects, and add to our understanding of ethanol's developmental stage-dependent neuroteratogenesis.

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

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

Magnetic resonance-based imaging in animal models of fetal alcohol spectrum disorder.

Magnetic resonance imaging (MRI) techniques, such as magnetic resonance microscopy (MRM), diffusion tensor imaging (DTI), and magnetic resonance spectroscopy (MRS), have recently been applied to the study of both normal and abnormal structure and neurochemistry in small animals. Herein, findings from studies in which these methods have been used for the examination of animal models of Fetal Alcohol Spectrum Disorder (FASD) are discussed. Emphasis is placed on results of imaging studies in fetal and postnatal mice that have highlighted the developmental stage dependency of prenatal ethanol exposure-induced CNS defects. Consideration is also given to the promise of methodological advances to allow in vivo studies of aberrant brain and behavior relationships in model animals and to the translational nature of this work.

Focus on: magnetic resonance-based studies of fetal alcohol spectrum disorders in animal models.

The imaging techniques magnetic resonance imaging (MRI), diffusion tensor imaging (DTI), and magnetic resonance spectroscopy (MRS) provide valuable tools for studying brain structure and neurochemistry in fetal alcohol spectrum disorders (FASD). Although the application of magnetic resonance-based methodologies to the study of FASD in animal models is in its infancy, it already has provided new clinically relevant insights and holds significant promise to further extend our understanding of alcohol's effects on the developing fetus.

Binge toluene exposure alters glutamate, glutamine and GABA in the adolescent rat brain as measured by proton magnetic resonance spectroscopy.

Despite the high incidence of toluene abuse in adolescents, little is known regarding the effect of binge exposure on neurochemical profiles during this developmental stage. In the current study, the effects of binge toluene exposure during adolescence on neurotransmitter levels were determined using high-resolution proton magnetic resonance spectroscopy ex vivo at 11.7T. Adolescent male Sprague-Dawley rats were exposed to toluene (0, 8000, or 12,000 ppm) for 15 min twice daily from postnatal day 28 (P28) through P34 and then euthanized either 1 or 7 days later (on P35 or P42) to assess glutamate (GLU), glutamine, and GABA levels in intact tissue punches from the medial prefrontal cortex (mPFC), anterior striatum and hippocampus. In the mPFC, toluene reduced GLU 1 day after exposure, with no effect on GABA, while after 7 days, GLU was no longer affected but there was an increase in GABA levels. In the hippocampus, neither GABA nor GLU was altered 1 day after exposure, whereas 7 days after exposure, increases were observed in GABA and GLU. Striatal GLU and GABA levels measured after either 1 or 7 days were not altered after toluene exposure. These findings show that 1 week of binge toluene inhalation selectively alters these neurotransmitters in the mPFC and hippocampus in adolescent rats, and that some of these effects endure at least 1 week after the exposure. The results suggest that age-dependent, differential neurochemical responses to toluene may contribute to the unique behavioral patterns associated with drug abuse among older children and young teens.

Ventromedian forebrain dysgenesis follows early prenatal ethanol exposure in mice.

Ethanol exposure on gestational day (GD) 7 in the mouse has previously been shown to result in ventromedian forebrain deficits along with facial anomalies characteristic of fetal alcohol syndrome (FAS). To further explore ethanol's teratogenic effect on the ventromedian forebrain in this mouse model, scanning electron microscopic and histological analyses were conducted. For this, time mated C57Bl/6J mice were injected with 2.9g/kg ethanol or saline twice, at a 4h interval, on their 7th day of pregnancy. On GD 12.5, 13 and 17, control and ethanol-exposed specimens were collected and processed for light and scanning electron microscopic analyses. Gross morphological changes present in the forebrains of ethanol-exposed embryos included cerebral hemispheres that were too close in proximity or rostrally united, enlarged foramina of Monro, enlarged or united lateral ventricles, and varying degrees of hippocampal and ventromedian forebrain deficiency. In GD 12.5 control and ethanol-exposed embryos, in situ hybridization employing probes for Nkx2.1 or Fzd8 to distinguish the preoptic area and medial ganglionic eminences (MGEs) from the lateral ganglionic eminences, respectively, confirmed the selective loss of ventromedian tissues. Immunohistochemical labeling of oligodendrocyte progenitors with Olig2, a transcription factor necessary for their specification, and of GABA, an inhibitory neurotransmitter, showed ethanol-induced reductions in both. To investigate later consequences of ventromedian forebrain loss, MGE-derived somatostatin-expressing interneurons in the subpallial region of GD 17 fetal mice were examined, with results showing that the somatostatin-expressing interneurons that were present were dysmorphic in the ethanol-exposed fetuses. The potential functional consequences of this insult are discussed.

Magnetic resonance microscopy-based analyses of the brains of normal and ethanol-exposed fetal mice.

BACKGROUND: The application of magnetic resonance microscopy (MRM) to the study of normal and abnormal prenatal mouse development has facilitated discovery of dysmorphology following prenatal ethanol insult. The current analyses extend this work, providing a regional brain volume-based description of normal brain growth and illustrating the consequences of gestational day (GD) 10 ethanol exposure in the fetal mouse. METHODS: To assess normal growth, control C57Bl/6J fetuses collected on GD 16, GD 16.5, and GD 17 were scanned using a 9.4-T magnet, resulting in 29-µm isotropic resolution images. For the ethanol teratogenicity studies, C57Bl/6J dams were administered intraperitoneal ethanol (2.9 g/kg) at 10 days, 0 hr, and 10 days, 4 hr, after fertilization, and fetuses were collected for analyses on GD 17. From individual MRM scans, linear measurements and regional brain volumes were determined and compared. RESULTS: In control fetuses, each of the assessed brain regions increased in volume, whereas ventricular volumes decreased between GD 16 and GD 17. Illustrating a global developmental delay, prenatal ethanol exposure resulted in reduced body volumes, crown-rump lengths, and a generalized decrease in regional brain volumes compared with GD 17 controls. However, compared with GD 16.5, morphologically matched controls, ethanol exposure resulted in volume increases in the lateral and third ventricles as well as a disproportionate reduction in cortical volume. CONCLUSIONS: The normative data collected in this study facilitate the distinction between GD 10 ethanol-induced developmental delay and frank dysmorphology. This work illustrates the utility of MRM-based analyses for developmental toxicology studies and extends our knowledge of the stage-dependency of ethanol teratogenesis.

Genesis of teratogen-induced holoprosencephaly in mice.

Evidence from mechanical, teratological, and genetic experimentation demonstrates that holoprosencephaly (HPE) typically results from insult prior to the time that neural tube closure is completed and occurs as a consequence of direct or indirect insult to the rostral prechordal cells that induce the forebrain or insult to the median forebrain tissue, itself. Here, we provide an overview of normal embryonic morphogenesis during the critical window for HPE induction, focusing on the morphology and positional relationship of the developing brain and subjacent prechordal plate and prechordal mesoderm cell populations. Subsequent morphogenesis of the HPE spectrum is then examined in selected teratogenesis mouse models. The temporal profile of Sonic Hedgehog expression in rostral embryonic cell populations and evidence for direct or indirect perturbation of the Hedgehog pathway by teratogenic agents in the genesis of HPE is highlighted. Emerging opportunities based on recent insights and new techniques to further characterize the mechanisms and pathogenesis of HPE are discussed.

Magnetic resonance microscopy defines ethanol-induced brain abnormalities in prenatal mice: effects of acute insult on gestational day 7.

BACKGROUND: This magnetic resonance microscopy (MRM)-based report is the second in a series designed to illustrate the spectrum of craniofacial and central nervous system (CNS) dysmorphia resulting from single- and multiple-day maternal ethanol treatment. The study described in this report examined the consequences of ethanol exposure on gestational day (GD) 7 in mice, a time in development when gastrulation and neural plate development begins; corresponding to the mid- to late third week postfertilization in humans. Acute GD 7 ethanol exposure in mice has previously been shown to result in CNS defects consistent with holoprosencephaly (HPE) and craniofacial anomalies typical of those in Fetal Alcohol Syndrome (FAS). MRM has facilitated further definition of the range of GD 7 ethanol-induced defects. METHODS: C57Bl/6J female mice were intraperitoneally (i.p.) administered vehicle or 2 injections of 2.9 g/kg ethanol on day 7 of pregnancy. Stage-matched control and ethanol-exposed GD 17 fetuses selected for imaging were immersion fixed in a Bouins/Prohance solution. MRM was conducted at either 7.0 Tesla (T) or 9.4 T. Resulting 29 microm isotropic spatial resolution scans were segmented and reconstructed to provide 3D images. Linear and volumetric brain measures, as well as morphological features, were compared for control and ethanol-exposed fetuses. Following MRM, selected specimens were processed for routine histology and light microscopic examination. RESULTS: Gestational day 7 ethanol exposure resulted in a spectrum of median facial and forebrain deficiencies, as expected. This range of abnormalities falls within the HPE spectrum; a spectrum for which facial dysmorphology is consistent with and typically is predictive of that of the forebrain. In addition, other defects including median facial cleft, cleft palate, micrognathia, pituitary agenesis, and third ventricular dilatation were identified. MRM analyses also revealed cerebral cortical dysplasia/heterotopias resulting from this acute, early insult and facilitated a subsequent focused histological investigation of these defects. CONCLUSIONS: Individual MRM scans and 3D reconstructions of fetal mouse brains have facilitated demonstration of a broad range of GD 7 ethanol-induced morphological abnormality. These results, including the discovery of cerebral cortical heterotopias, elucidate the teratogenic potential of ethanol insult during the third week of human prenatal development.

Neurochemical changes after acute binge toluene inhalation in adolescent and adult rats: a high-resolution magnetic resonance spectroscopy study.

Inhalant abuse in young people is a growing public health concern. We reported previously that acute toluene intoxication in young rats, using a pattern of exposures that approximate abuse patterns of inhalant use in humans, significantly altered neurochemical measures in select brain regions. In this study, adolescent and young adult rats were exposed similarly to an acute (2 x 15 min), high dose (8000-12,000 ppm) of toluene and high-resolution magic angle spinning proton magnetic resonance spectroscopy (HR-MAS 1H-MRS) was used to assess neurochemical profiles of tissue samples from a number of brain regions collected immediately following solvent exposure. The current investigation focused on N-acetyl-aspartate (NAA), choline-containing compounds, creatine, glutamate, GABA, and glutamine. Contrary to our predictions, no significant alterations were found in the levels of NAA, choline, creatine, glutamate, or glutamine in adolescent animals. In contrast to these minimal effects in adolescents, binge toluene exposure altered several neurochemical parameters in young adult rats, including decreased levels of choline and GABA in the frontal cortex and striatum and lowered glutamine and NAA levels in the frontal cortex. One of the more robust findings was a wide-ranging increase in lactate after toluene exposure in adult animals, an effect not observed in adolescents. These age-dependent effects of toluene are distinct from those reported previously in juvenile rats and suggest a developmental difference in vulnerability to the effects of inhalants. Specifically, the results suggest that the neurochemical response to toluene in adolescents is attenuated compared to adults, and imply an association between these neurochemical differences and age-influenced differences in solvent abuse in humans.

Magnetic resonance microscopy defines ethanol-induced brain abnormalities in prenatal mice: effects of acute insult on gestational day 8.

BACKGROUND: Magnetic resonance microscopy (MRM), magnetic resonance imaging (MRI) at microscopic levels, provides unprecedented opportunities to aid in defining the full spectrum of ethanol's insult to the developing brain. This is the first in a series of reports that, collectively, will provide an MRM-based atlas of developmental stage-dependent structural brain abnormalities in a Fetal Alcohol Spectrum Disorders (FASD) mouse model. The ethanol exposure time and developmental stage examined for this report is gestational day (GD) 8 in mice, when the embryos are at early neurulation stages; stages present in humans early in the fourth week postfertilization. METHODS: For this study, pregnant C57Bl/6J mice were administered an ethanol dosage of 2.8 g/kg intraperitoneally at 8 days, 0 hour and again at 8 days, 4 hours postfertilization. On GD 17, fetuses that were selected for MRM analyses were immersion fixed in a Bouin's/Prohance solution. Control fetuses from vehicle-treated dams were stage-matched to those that were ethanol-exposed. The fetal mice were scanned ex vivo at 7.0 T and 512 x 512 x 1024 image arrays were acquired using 3-D spin warp encoding. The resulting 29 microm (isotropic) resolution images were processed using ITK-SNAP, a 3-D segmentation/visualization tool. Linear and volume measurements were determined for selected brain, head, and body regions of each specimen. Comparisons were made between control and treated fetuses, with an emphasis on determining (dis)proportionate changes in specific brain regions. RESULTS: As compared with controls, the crown-rump lengths of stage-matched ethanol-exposed GD 17 fetuses were significantly reduced, as were brain and whole body volumes. Volume reductions were notable in every brain region examined, with the exception of the pituitary and septal region, and were accompanied by increased ventricular volumes. Disproportionate regional brain volume reductions were most marked on the right side and were significant for the olfactory bulb, hippocampus, and cerebellum; the latter being the most severely affected. Additionally, the septal region and the pituitary were disproportionately large. Linear measures were consistent with those of volume. Other dysmorphologic features noted in the MR scans were choanal stenosis and optic nerve coloboma. CONCLUSIONS: This study demonstrates that exposure to ethanol occurring in mice at stages corresponding to the human fourth week postfertilization results in structural brain abnormalities that are readily identifiable at fetal stages of development. In addition to illustrating the utility of MR microscopy for analysis of an FASD mouse model, this work provides new information that confirms and extends human clinical observations. It also provides a framework for comparison of structural brain abnormalities resulting from ethanol exposure at other developmental stages and dosages.

Neonatal alcohol-induced region-dependent changes in rat brain neurochemistry measured by high-resolution magnetic resonance spectroscopy.

BACKGROUND: Maternal drinking during pregnancy can lead to a range of deleterious outcomes in the developing offspring that have been collectively termed fetal alcohol spectrum disorders (FASDs). There is interest and recognized value in using non-invasive neuroimaging techniques such as magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) to characterize, respectively, structural and biochemical alterations in individuals with FASDs. To date, however, results with MRS have been inconsistent regarding the degree and/or nature of abnormalities. METHODS: High-resolution magic angle spinning (HR-MAS) proton ((1)H) MRS is an ex vivo neuroimaging technique that can acquire spectra in small punches of intact tissue, providing clinically relevant neurochemical information about discrete brain regions. In this study, HR-MAS (1)H MRS was used to examine regional neurochemistry in frontal cortex, striatum, hippocampus, and cerebellum of young rats previously exposed to ethanol as neonates. Key neurochemicals of interest included N-acetyl-aspartate (NAA), glutamate, GABA, glutamine, creatine, choline and myo-inositol. RESULTS: Daily neonatal alcohol exposure from postnatal day 4 (PN4) through PN9 significantly reduced levels of NAA and taurine in the cerebellum and striatum, and induced sex-dependent reductions in cerebellar glutamate when measured on PN16. In addition, myo-inositol was significantly increased in cerebellum. The frontal cortex and hippocampus were virtually unaffected by this neonatal alcohol exposure. CONCLUSION: Results of this research may have implications for understanding the underlying neurobiology associated with FASDs and aid in testing treatments in the future. Ongoing studies are assessing the developmental persistence of and/or maturational recovery from these changes.

Postnatal environmental or experiential amelioration of neurobehavioral effects of perinatal alcohol exposure in rats.

Fetal alcohol spectrum disorders (FASDs) in children are characterized by life-long compromises in learning, memory, and adaptive responses. To date, there are no clinical remedies for the treatment of global fetal alcohol effects, although interventions for specific outcomes are available. Here we review basic research in animal models of perinatal alcohol exposure to assess the potential of global environmental manipulations to ameliorate the neurobehavioral effects associated with FASD. Enhancement of the postnatal environment via neonatal handling, environmental enrichment, or rehabilitative or "therapeutic" motor training, can improve behavioral performance and ameliorate or even eliminate some deficits in perinatal alcohol-exposed rats and mice. While neuroanatomical changes associated with the behavioral improvements have been reported in some models, there generally appears to be a persistent impairment in neuronal plasticity. Such research suggests that it may be possible to manage the postnatal environment or experience of children with FASDs to improve function. It is, however, necessary to consider the difficulties in translating findings from research in animals to the clinic, school or home because sex-, postnatal age- and species-specific differences are critical factors in how specific environments may influence brain development. Continued study of the potential ameliorative effects of neonatal handling, environmental enrichment, and rehabilitative training as "therapies" in animal models will remain a valuable source of information for eventually devising treatments for children with FASDs.

Reversal learning after prenatal or early postnatal alcohol exposure in juvenile and adult rats.

Learning tasks that require the reversal of a previously learned contingency are disrupted in animals and humans exposed to alcohol during the perinatal period. The current experiments examined how varying the time of alcohol exposure and the age at which subjects were tested would affect the expression of reversal deficits in a T-maze task. Groups of rats were exposed to alcohol from gestational day (GD) 8 to GD20 or from postnatal day (PN) 4 to PN9, and then tested in a spatial reversal task at either PN28 or PN63. Results indicate that exposure to alcohol during the prenatal period did not lead to substantial dose-dependent reversal learning deficits in males or females at either age tested. However, exposure to alcohol during the early postnatal period, a period that corresponds to the third trimester in human neural development, selectively disrupted reversal learning performance in male rats at PN28 but not PN63. Statistically significant sex differences were seen when subjects were tested at PN63. These results demonstrate how the timing of alcohol exposure leads to variability in the age-dependent expression of learning deficits associated with fetal alcohol effects.

Effects of prenatal alcohol exposure on forepaw digit length and digit ratios in rats.

Prenatal exposure to alcohol can cause limb and digit defects. Variations in digit ratios in humans are associated with prenatal testosterone exposure. Since prenatal alcohol can reduce testosterone in rats, the effects of prenatal alcohol were measured on rat digit length. Pregnant Sprague-Dawley rats were intubated with 0 g/kg, 4 g/kg, or 6 g/kg of ethanol from Gestational Day 8 (GD8) to GD20. The 0-g/kg group and a nonintubated group served as controls. At postnatal day 31, forepaw digit lengths were measured and digit ratios calculated. Females had smaller digits on both forepaws and higher digit ratios on the right forepaw than males. Rats exposed to 6 g/kg of ethanol had smaller digits than controls on both forepaws and higher digit ratios than controls on the left forepaw. Rat digit ratios differ between the sexes, and prenatal alcohol exposure affects digit ratios. The results are consistent with a perinatal disruption of testosterone levels by alcohol and/or of testosterone's effects on digit length and ratios. An alternate interpretation is consistent with a retinoic acid-mediated effect of alcohol on digit length and ratios.