Enhanced Deficits in Long-Term Potentiation in the Adult Dentate Gyrus with 2 Trimester Ethanol Consumption

Department of Biology, University of Victoria, Victoria, British Columbia, Canada.
PLoS ONE (Impact Factor: 3.23). 12/2012; 7(12):e51344. DOI: 10.1371/journal.pone.0051344
Source: PubMed


Ethanol exposure during pregnancy can cause structural and functional changes in the brain that can impair cognitive capacity. The hippocampal formation, an area of the brain strongly linked with learning and memory, is particularly vulnerable to the teratogenic effects of ethanol. In the present experiments we sought to determine if the functional effects of developmental ethanol exposure could be linked to ethanol exposure during any single trimester-equivalent. Ethanol exposure during the 1(st) or 3(rd) trimester-equivalent produced only minor changes in synaptic plasticity in adult offspring. In contrast, ethanol exposure during the 2(nd) trimester equivalent resulted in a pronounced decrease in long-term potentiation, indicating that the timing of exposure influences the severity of the deficit. Together, the results from these experiments demonstrate long-lasting alterations in synaptic plasticity as the result of developmental ethanol exposure and dependent on the timing of exposure. Furthermore, these results allude to neural circuit malfunction within the hippocampal formation, perhaps relating to the learning and memory deficits observed in individuals with fetal alcohol spectrum disorders.

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    • "Recent studies suggest that the long-lasting progenitors within the adult SGZ originate from a distinct population of neural stem cells within the ventral hippocampus generated during the perinatal period [51]. Synaptic input from the entorhinal cortex begins during late gestational periods in the rodent and continues to reach adult levels by postnatal day 25 in the rat [52]. Clearly, alcohol exposure during late gestation vs. early postnatal periods could influence distinct aspects of dentate development that lead to long-lasting deficits in neurogenesis that may manifest with distinct characteristics. "
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    ABSTRACT: Prenatal alcohol exposure can lead to fetal alcohol spectrum disorder (FASD) and associated behavioral impairments that may be linked to disruptions in adult hippocampal neurogenesis. Social and physical enrichment has been proposed as a potential therapeutic approach toward reversing behavioral deficits associated with FASD and is also a potent stimulator of adult hippocampal neurogenesis. In the present study, we utilized a genetic fate mapping approach in nestin-CreER(T2)/YFP bitransgenic mice to identify the stage-specific impact of prenatal alcohol exposure on the stepwise maturation of adult hippocampal progenitors. Using a limited alcohol access "drinking-in-the-dark" model of FASD, we confirm previous findings that moderate prenatal alcohol exposure has no effect on adult neurogenesis under standard housing conditions, but abolishes the neurogenic response to enriched environment (EE). Furthermore, we demonstrate that this effect is primarily due to failed EE-mediated survival of postmitotic neurons. Finally, we demonstrate that the neurogenic deficit is associated with impaired spatial pattern recognition, as demonstrated by delayed learning of FASD-EE mice in an A-B contextual discrimination task. These results identify a potential maturational stage-specific mechanism(s) underlying impaired neurogenic function in a preclinical model of FASD, and provide a basis for testing regulatory pathways in this model through conditional and inducible manipulation of gene expression in the adult hippocampal progenitor population.
    Preview · Article · Sep 2013 · PLoS ONE
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    ABSTRACT: Alcohol consumption during pregnancy has deleterious effects on the developing foetus ranging from subtle physical deficits to severe behavioural abnormalities and are encompassed under a broad umbrella term, Foetal Alcohol Spectrum Disorders (FASD). High levels of exposure show distinct effects, whereas the consequences of moderate exposures have been less well studied. The aim of this study was to examine the effects of a moderate dose ethanol exposure using an ad libitum drinking procedure during the first eight days of gestation in mice on the behavioural phenotype of adult offspring. Adult female C57Bl/6J mice were mated and exposed to either 10% (v/v) ethanol or water for the first 8 days of gestation (GD0-8), and then offered water for the rest of gestation. Early developmental milestone achievement was assessed in offspring at postnatal days (P) 7, 14 and 21. Adult offspring underwent a comprehensive battery of behavioural tests to examine a range of behavioural domains including locomotion, exploration, anxiety, social behaviour, learned helplessness, sensorimotor gating, and nociception, as well as spatial memory in a water maze. Ethanol-exposed mice had similar postnatal developmental trajectories to water-exposed mice. However, the ethanol-exposed mice showed increased hyperlocomotion at P 14, 21 and 70 (p<0.05). Increased exploration and heightened motivation were also observed in adult mice. Furthermore, ethanol-exposed mice showed a significant improvement in memory in the water maze. The main findings were that mice had persistent and long lasting alterations in behaviour, including hyperactivity and enhanced spatial memory. These data suggest that even moderate dose ethanol exposure in early gestation has long term consequences on brain function and behaviour in mice.
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    ABSTRACT: Ethanol is known as a potent teratogen responsible for the fetal alcohol syndrome characterized by cognitive deficits especially pronounced in juveniles but ameliorating in adults. Since the mechanisms of these deficits and following partial recovery are not fully elucidated, the aim of the present study was to investigate the process of synaptogenesis in the hippocampus over the first two months of life in control and fetal-alcohol rats. Ethanol was delivered to the pregnant dams by intragastric intubation throughout 7-21 gestation days at the daily dose of 6g/kg generating a mean blood alcohol level of 246.6±40.9mg/dl on gestation day 20. The spine densities as well as the expression of pre- and postsynaptic proteins, synaptophysin (SYP) and PSD-95 protein, were evaluated for three distinct hippocampal regions: CA1, CA2+3, and DG and four postnatal days: PD1, PD10, PD30 and PD60, independently. Our results confirmed an intensive synaptogenesis within the brain spurt period (first 10 postnatal days), however, the temporal pattern of changes in the SYP and PSD-95 expression was different. The ethanol exposure during half of the 1(st) and the whole 2(nd) human trimester equivalent resulted in an overall trend towards lower values of synaptic indices at PD1 with a fast recovery from these deficits observed already at PD10. At PD30, around the age when the most pronounced behavioral deficits have been previously reported in juvenile fetal-alcohol subjects, no significant changes were found in either the hippocampal levels of synaptic proteins or in the spine density in principal hippocampal neurons.
    No preview · Article · Dec 2013 · International journal of developmental neuroscience: the official journal of the International Society for Developmental Neuroscience
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