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Basavarajappa BS, Subbanna S. Synaptic Plasticity Abnormalities in Fetal Alcohol Spectrum Disorders. Cells 2023; 12:442. [PMID: 36766783 PMCID: PMC9913617 DOI: 10.3390/cells12030442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 01/10/2023] [Accepted: 01/27/2023] [Indexed: 01/31/2023] Open
Abstract
The brain's ability to strengthen or weaken synaptic connections is often termed synaptic plasticity. It has been shown to function in brain remodeling following different types of brain damage (e.g., drugs of abuse, alcohol use disorders, neurodegenerative diseases, and inflammatory conditions). Although synaptic plasticity mechanisms have been extensively studied, how neural plasticity can influence neurobehavioral abnormalities in alcohol use disorders (AUDs) is far from being completely understood. Alcohol use during pregnancy and its harmful effects on the developing offspring are major public health, social, and economic challenges. The significant attribute of prenatal alcohol exposure on offspring is damage to the central nervous system (CNS), causing a range of synaptic structural, functional, and behavioral impairments, collectively called fetal alcohol spectrum disorder (FASD). Although the synaptic mechanisms in FASD are limited, emerging evidence suggests that FASD pathogenesis involves altering a set of molecules involved in neurotransmission, myelination, and neuroinflammation. These studies identify several immediate and long-lasting changes using many molecular approaches that are essential for synaptic plasticity and cognitive function. Therefore, they can offer potential synaptic targets for the many neurobehavioral abnormalities observed in FASD. In this review, we discuss the substantial research progress in different aspects of synaptic and molecular changes that can shed light on the mechanism of synaptic dysfunction in FASD. Increasing our understanding of the synaptic changes in FASD will significantly advance our knowledge and could provide a basis for finding novel therapeutic targets and innovative treatment strategies.
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Affiliation(s)
- Balapal S. Basavarajappa
- Center for Dementia Research, Nathan Kline Institute for Psychiatric Research, Orangeburg, NY 10962, USA
- Molecular Imaging and Neuropathology Area, New York State Psychiatric Institute, New York, NY 10032, USA
- Department of Psychiatry, Columbia University Irving Medical Center, New York, NY 10032, USA
- Department of Psychiatry, New York University Langone Medical Center, New York, NY 10016, USA
| | - Shivakumar Subbanna
- Center for Dementia Research, Nathan Kline Institute for Psychiatric Research, Orangeburg, NY 10962, USA
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Binge-like Prenatal Ethanol Exposure Causes Impaired Cellular Differentiation in the Embryonic Forebrain and Synaptic and Behavioral Defects in Adult Mice. Brain Sci 2022; 12:brainsci12060793. [PMID: 35741678 PMCID: PMC9220802 DOI: 10.3390/brainsci12060793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 06/10/2022] [Accepted: 06/15/2022] [Indexed: 11/30/2022] Open
Abstract
An embryo’s in-utero exposure to ethanol due to a mother’s alcohol drinking results in a range of deficits in the child that are collectively termed fetal alcohol spectrum disorders (FASDs). Prenatal ethanol exposure is one of the leading causes of preventable intellectual disability. Its neurobehavioral underpinnings warrant systematic research. We investigated the immediate effects on embryos of acute prenatal ethanol exposure during gestational days (GDs) and the influence of such exposure on persistent neurobehavioral deficits in adult offspring. We administered pregnant C57BL/6J mice with ethanol (1.75 g/kg) (GDE) or saline (GDS) intraperitoneally (i.p.) at 0 h and again at 2 h intervals on GD 8 and GD 12. Subsequently, we assessed apoptosis, differentiation, and signaling events in embryo forebrains (E13.5; GD13.5). Long-lasting effects of GDE were evaluated via a behavioral test battery. We also determined the long-term potentiation and synaptic plasticity-related protein expression in adult hippocampal tissue. GDE caused apoptosis, inhibited differentiation, and reduced pERK and pCREB signaling and the expression of transcription factors Pax6 and Lhx2. GDE caused persistent spatial and social investigation memory deficits compared with saline controls, regardless of sex. Interestingly, GDE adult mice exhibited enhanced repetitive and anxiety-like behavior, irrespective of sex. GDE reduced synaptic plasticity-related protein expression and caused hippocampal synaptic plasticity (LTP and LTD) deficits in adult offspring. These findings demonstrate that binge-like ethanol exposure at the GD8 and GD12 developmental stages causes defects in pERK–pCREB signaling and reduces the expression of Pax6 and Lhx2, leading to impaired cellular differentiation during the embryonic stage. In the adult stage, binge-like ethanol exposure caused persistent synaptic and behavioral abnormalities in adult mice. Furthermore, the findings suggest that combining ethanol exposure at two sensitive stages (GD8 and GD12) causes deficits in synaptic plasticity-associated proteins (Arc, Egr1, Fgf1, GluR1, and GluN1), leading to persistent FASD-like neurobehavioral deficits in mice.
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Delatour LC, Yeh PWL, Yeh HH. Prenatal Exposure to Ethanol Alters Synaptic Activity in Layer V/VI Pyramidal Neurons of the Somatosensory Cortex. Cereb Cortex 2020; 30:1735-1751. [PMID: 31647550 PMCID: PMC7132917 DOI: 10.1093/cercor/bhz199] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Revised: 07/04/2019] [Accepted: 08/04/2019] [Indexed: 12/31/2022] Open
Abstract
Fetal alcohol spectrum disorder (FASD) encompasses a range of cognitive and behavioral deficits, with aberrances in the function of cerebral cortical pyramidal neurons implicated in its pathology. However, the mechanisms underlying these aberrances, including whether they persist well beyond ethanol exposure in utero, remain to be explored. We addressed these issues by employing a mouse model of FASD in which pregnant mice were exposed to binge-type ethanol from embryonic day 13.5 through 16.5. In both male and female offspring (postnatal day 28-32), whole-cell patch clamp recording of layer V/VI somatosensory cortex pyramidal neurons revealed increases in the frequency of excitatory and inhibitory postsynaptic currents. Furthermore, expressing channelrhodopsin in either GABAergic interneurons (Nkx2.1Cre-Ai32) or glutamatergic pyramidal neurons (Emx1IRES Cre-Ai32) revealed a shift in optically evoked paired-pulse ratio. These findings are consistent with an excitatory-inhibitory imbalance with prenatal ethanol exposure due to diminished inhibitory but enhanced excitatory synaptic strength. Prenatal ethanol exposure also altered the density and morphology of spines along the apical dendrites of pyramidal neurons. Thus, while both presynaptic and postsynaptic mechanisms are affected following prenatal exposure to ethanol, there is a prominent presynaptic component that contributes to altered inhibitory and excitatory synaptic transmission in the somatosensory cortex.
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Affiliation(s)
- Laurie C Delatour
- Department of Molecular and Systems Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755, USA
| | - Pamela W L Yeh
- Department of Molecular and Systems Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755, USA
| | - Hermes H Yeh
- Department of Molecular and Systems Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755, USA
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Andersen SL. Stress, sensitive periods, and substance abuse. Neurobiol Stress 2019; 10:100140. [PMID: 30569003 PMCID: PMC6288983 DOI: 10.1016/j.ynstr.2018.100140] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 08/18/2018] [Accepted: 11/26/2018] [Indexed: 12/14/2022] Open
Abstract
Research on the inter-relationship between drug abuse and social stress has primarily focused on the role of stress exposure during adulthood and more recently, adolescence. Adolescence is a time of heightened reward sensitivity, but it is also a time when earlier life experiences are expressed. Exposure to stress early in postnatal life is associated with an accelerated age of onset for drug use. Lifelong addiction is significantly greater if drug use is initiated during early adolescence. Understanding how developmental changes following stress exposure interact with sensitive periods to unfold over the course of maturation is integral to reducing their later impact on substance use. Arousal levels, gender/sex, inflammation, and the timing of stress exposure play a role in the vulnerability of these circuits. The current review focuses on how early postnatal stress impacts brain development during a sensitive period to increase externalizing and internalizing behaviors in adolescence that include social interactions (aggression; sexual activity), working memory impairment, and depression. How stress effects the developmental trajectories of brain circuits that are associated with addiction are discussed for both clinical and preclinical studies.
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Jablonski SA, Robinson-Drummer PA, Schreiber WB, Asok A, Rosen JB, Stanton ME. 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. Behav Neurosci 2018; 132:497-511. [PMID: 30346189 DOI: 10.1037/bne0000272] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
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).
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Affiliation(s)
| | | | | | - Arun Asok
- Department of Psychological and Brain Sciences
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Naassila M, Pierrefiche O. GluN2B Subunit of the NMDA Receptor: The Keystone of the Effects of Alcohol During Neurodevelopment. Neurochem Res 2018; 44:78-88. [DOI: 10.1007/s11064-017-2462-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 12/18/2017] [Accepted: 12/26/2017] [Indexed: 12/18/2022]
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Long Term Depression in Rat Hippocampus and the Effect of Ethanol during Fetal Life. Brain Sci 2017; 7:brainsci7120157. [PMID: 29182556 PMCID: PMC5742760 DOI: 10.3390/brainsci7120157] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 11/20/2017] [Accepted: 11/27/2017] [Indexed: 12/11/2022] Open
Abstract
Alcohol (ethanol) disturbs cognitive functions including learning and memory in humans, non-human primates, and laboratory animals such as rodents. As studied in animals, cellular mechanisms for learning and memory include bidirectional synaptic plasticity, long-term potentiation (LTP), and long-term depression (LTD), primarily in the hippocampus. Most of the research in the field of alcohol has analyzed the effects of ethanol on LTP; however, with recent advances in the understanding of the physiological role of LTD in learning and memory, some authors have examined the effects of ethanol exposure on this particular signal. In the present review, I will focus on hippocampal LTD recorded in rodents and the effects of fetal alcohol exposure on this signal. A synthesis of the findings indicates that prenatal ethanol exposure disturbs LTD concurrently with LTP in offspring and that both glutamatergic and γ-aminobutyric acid (GABA) neurotransmissions are altered and contribute to LTD disturbances. Although the ultimate mode of action of ethanol on these two transmitter systems is not yet clear, novel suggestions have recently appeared in the literature.
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Goodfellow MJ, Abdulla KA, Lindquist DH. Neonatal Ethanol Exposure Impairs Trace Fear Conditioning and Alters NMDA Receptor Subunit Expression in Adult Male and Female Rats. Alcohol Clin Exp Res 2016; 40:309-18. [DOI: 10.1111/acer.12958] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2015] [Accepted: 11/04/2015] [Indexed: 01/10/2023]
Affiliation(s)
| | - Khalid A. Abdulla
- Department of Psychology; The Ohio State University; Columbus Ohio
- Department of Neuroscience; The Ohio State University; Columbus Ohio
| | - Derick H. Lindquist
- Department of Psychology; The Ohio State University; Columbus Ohio
- Department of Neuroscience; The Ohio State University; Columbus Ohio
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Sadrian B, Lopez-Guzman M, Wilson DA, Saito M. Distinct neurobehavioral dysfunction based on the timing of developmental binge-like alcohol exposure. Neuroscience 2014; 280:204-19. [PMID: 25241068 DOI: 10.1016/j.neuroscience.2014.09.008] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Revised: 09/03/2014] [Accepted: 09/05/2014] [Indexed: 12/24/2022]
Abstract
Gestational exposure to alcohol can result in long-lasting behavioral deficiencies generally described as fetal alcohol spectrum disorder (FASD). FASD-modeled rodent studies of acute ethanol exposure typically select one developmental window to simulate a specific context equivalent of human embryogenesis, and study consequences of ethanol exposure within that particular developmental epoch. Exposure timing is likely a large determinant in the neurobehavioral consequence of early ethanol exposure, as each brain region is variably susceptible to ethanol cytotoxicity and has unique sensitive periods in their development. We made a parallel comparison of the long-term effects of single-day binge ethanol at either embryonic day 8 (E8) or postnatal day 7 (P7) in male and female mice, and here demonstrate the differential long-term impacts on neuroanatomy, behavior and in vivo electrophysiology of two systems with very different developmental trajectories. The significant long-term differences in odor-evoked activity, local circuit inhibition, and spontaneous coherence between brain regions in the olfacto-hippocampal pathway that were found as a result of developmental ethanol exposure, varied based on insult timing. Long-term effects on cell proliferation and interneuron cell density were also found to vary by insult timing as well as by region. Finally, spatial memory performance and object exploration were affected in P7-exposed mice, but not E8-exposed mice. Our physiology and behavioral results are conceptually coherent with the neuroanatomical data attained from these same mice. Our results recognize both variable and shared effects of ethanol exposure timing on long-term circuit function and their supported behavior.
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Affiliation(s)
- B Sadrian
- Department of Child and Adolescent Psychiatry, NYU School of Medicine, New York, NY, United States; Nathan Kline Institute for Psychiatric Research, Orangeburg, NY, United States.
| | - M Lopez-Guzman
- Nathan Kline Institute for Psychiatric Research, Orangeburg, NY, United States
| | - D A Wilson
- Department of Child and Adolescent Psychiatry, NYU School of Medicine, New York, NY, United States; Nathan Kline Institute for Psychiatric Research, Orangeburg, NY, United States
| | - M Saito
- Nathan Kline Institute for Psychiatric Research, Orangeburg, NY, United States; Department of Psychiatry, NYU School of Medicine, New York, NY, United States
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Ethanol neurotoxicity in the developing cerebellum: underlying mechanisms and implications. Brain Sci 2013; 3:941-63. [PMID: 24961432 PMCID: PMC4061865 DOI: 10.3390/brainsci3020941] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Revised: 05/08/2013] [Accepted: 06/04/2013] [Indexed: 01/18/2023] Open
Abstract
Ethanol is the main constituent of alcoholic beverages that exerts toxicity to neuronal development. Ethanol affects synaptogenesis and prevents proper brain development. In humans, synaptogenesis takes place during the third trimester of pregnancy, and in rodents this period corresponds to the initial few weeks of postnatal development. In this period neuronal maturation and differentiation begin and neuronal cells start migrating to their ultimate destinations. Although the neuronal development of all areas of the brain is affected, the cerebellum and cerebellar neurons are more susceptible to the damaging effects of ethanol. Ethanol’s harmful effects include neuronal cell death, impaired differentiation, reduction of neuronal numbers, and weakening of neuronal plasticity. Neuronal development requires many hormones and growth factors such as retinoic acid, nerve growth factors, and cytokines. These factors regulate development and differentiation of neurons by acting through various receptors and their signaling pathways. Ethanol exposure during development impairs neuronal signaling mechanisms mediated by the N-methyl-d-aspartate (NMDA) receptors, the retinoic acid receptors, and by growth factors such as brain-derived neurotrophic factor (BDNF), insulin-like growth factor 1 (IGF-I), and basic fibroblast growth factor (bFGF). In combination, these ethanol effects disrupt cellular homeostasis, reduce the survival and migration of neurons, and lead to various developmental defects in the brain. Here we review the signaling mechanisms that are required for proper neuronal development, and how these processes are impaired by ethanol resulting in harmful consequences to brain development.
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Sadrian B, Wilson DA, Saito M. Long-lasting neural circuit dysfunction following developmental ethanol exposure. Brain Sci 2013; 3:704-27. [PMID: 24027632 PMCID: PMC3767176 DOI: 10.3390/brainsci3020704] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Revised: 04/10/2013] [Accepted: 04/23/2013] [Indexed: 01/14/2023] Open
Abstract
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.
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Affiliation(s)
- Benjamin Sadrian
- Department of Child and Adolescent Psychiatry, New York University Langone School of Medicine, One Park Avenue, Eighth Floor, New York, NY 10128, USA; E-Mail:
- Nathan Kline Institute, 140 Old Orangeburg Road, Orangeburg, NY 10962, USA; E-Mail:
| | - Donald A. Wilson
- Department of Child and Adolescent Psychiatry, New York University Langone School of Medicine, One Park Avenue, Eighth Floor, New York, NY 10128, USA; E-Mail:
- Nathan Kline Institute, 140 Old Orangeburg Road, Orangeburg, NY 10962, USA; E-Mail:
| | - Mariko Saito
- Nathan Kline Institute, 140 Old Orangeburg Road, Orangeburg, NY 10962, USA; E-Mail:
- Department of Psychiatry, New York University Langone School of Medicine, One Park Avenue, Eighth Floor, New York, NY 10128, USA
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Hippocampal-dependent Pavlovian conditioning in adult rats exposed to binge-like doses of ethanol as neonates. Behav Brain Res 2012; 242:191-9. [PMID: 23274841 DOI: 10.1016/j.bbr.2012.12.030] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2012] [Revised: 12/12/2012] [Accepted: 12/13/2012] [Indexed: 01/13/2023]
Abstract
Binge-like postnatal ethanol exposure produces significant damage throughout the brain in rats, including the cerebellum and hippocampus. In the current study, cue- and context-mediated Pavlovian conditioning were assessed in adult rats exposed to moderately low (3E; 3g/kg/day) or high (5E; 5g/kg/day) doses of ethanol across postnatal days 4-9. Ethanol-exposed and control groups were presented with 8 sessions of trace eyeblink conditioning followed by another 8 sessions of delay eyeblink conditioning, with an altered context presented over the last two sessions. Both forms of conditioning rely on the brainstem and cerebellum, while the more difficult trace conditioning also requires the hippocampus. The hippocampus is also needed to gate or modulate expression of the eyeblink conditioned response (CR) based on contextual cues. Results indicate that the ethanol-exposed rats were not significantly impaired in trace EBC relative to control subjects. In terms of CR topography, peak amplitude was significantly reduced by both doses of alcohol, whereas onset latency but not peak latency was significantly lengthened in the 5E rats across the latter half of delay EBC in the original training context. Neither dosage resulted in significant impairment in the contextual gating of the behavioral response, as revealed by similar decreases in CR production across all four treatment groups following introduction of the novel context. Results suggest ethanol-induced brainstem-cerebellar damage can account for the present results, independent of the putative disruption in hippocampal development and function proposed to occur following postnatal ethanol exposure.
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Nixon K, Morris SA, Liput DJ, Kelso ML. Roles of neural stem cells and adult neurogenesis in adolescent alcohol use disorders. Alcohol 2010; 44:39-56. [PMID: 20113873 DOI: 10.1016/j.alcohol.2009.11.001] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2009] [Revised: 10/24/2009] [Accepted: 11/07/2009] [Indexed: 01/19/2023]
Abstract
This review discusses the contributions of a newly considered form of plasticity, the ongoing production of new neurons from neural stem cells, or adult neurogenesis, within the context of neuropathologies that occur with excessive alcohol intake in the adolescents. Neural stem cells and adult neurogenesis are now thought to contribute to the structural integrity of the hippocampus, a limbic system region involved in learning, memory, behavioral control, and mood. In adolescents with alcohol use disorders (AUDs), the hippocampus appears to be particularly vulnerable to the neurodegenerative effects of alcohol, but the role of neural stem cells and adult neurogenesis in alcoholic neuropathology has only recently been considered. This review encompasses a brief overview of neural stem cells and the processes involved in adult neurogenesis, how neural stem cells are affected by alcohol, and possible differences in the neurogenic niche between adults and adolescents. Specifically, what is known about developmental differences in adult neurogenesis between the adult and adolescent is gleaned from the literature, as well as how alcohol affects this process differently among the age groups. Finally, this review suggests differences that may exist in the neurogenic niche between adults and adolescents and how these differences may contribute to the susceptibility of the adolescent hippocampus to damage. However, many more studies are needed to discern whether these developmental differences contribute to the vulnerability of the adolescent to developing an AUD.
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Medina AE, Krahe TE. Neocortical plasticity deficits in fetal alcohol spectrum disorders: lessons from barrel and visual cortex. J Neurosci Res 2008; 86:256-63. [PMID: 17671993 DOI: 10.1002/jnr.21447] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Fetal Alcohol Spectrum Disorder (FASD) is characterized by a constellation of behavioral and physiological abnormalities, including learning and sensory deficits. There is growing evidence that abnormalities of neuronal plasticity underlie these deficits. However, the cellular and molecular mechanisms by which prenatal alcohol exposure disrupts neuronal plasticity remain elusive. Recently, studies with the barrel and the visual cortex as models to study the effects of early alcohol exposure on neuronal plasticity shed light on this subject. In this Mini-Review, we discuss the effects of ethanol exposure during development on neuronal plasticity and suggest environmental and pharmacological approaches to ameliorate these problems.
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Affiliation(s)
- Alexandre E Medina
- Department of Anatomy and Neurobiology, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298-0709, USA.
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Mello CF, Rubin MA, Sultana R, Barron S, Littleton JM, Butterfield DA. Difluoromethylornithine decreases long-lasting protein oxidation induced by neonatal ethanol exposure in the hippocampus of adolescent rats. Alcohol Clin Exp Res 2007; 31:887-94. [PMID: 17386069 DOI: 10.1111/j.1530-0277.2007.00369.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Ethanol exposure and withdrawal during central nervous system development can cause oxidative stress and produce severe and long-lasting behavioral and morphological alterations in which polyamines seem to play an important role. However, it is not known if early ethanol exposure causes long-lasting protein oxidative damage and if polyamines play a role in such a deleterious effect of ethanol. METHODS In this study we investigated the effects of early ethanol exposure (6 g/kg/d, by gavage), from postnatal day (PND) 1 to 8, and of the administration of difluoromethylornithine (DFMO, 500 mg/kg, i.p., on PND 8), a polyamine biosynthesis inhibitor, on the extent of oxidative modification of proteins. Indices of oxidative modification of proteins included protein carbonyls, 3-nitrotyrosine (3-NT), and protein bound 4-hydroxynonenal (HNE) in the hippocampus, cerebellum, hypothalamus, striatum, and cerebral cortex of Sprague-Dawley rats at PND 40. RESULTS Both ethanol and DFMO administration alone increased protein carbonyl immunoreactivity in the hippocampus at PND 40, but the combination of DFMO and ethanol resulted in no effect on protein carbonyl levels. No alterations in the content of protein-bound HNE, 3-NT, or carbonyl were found in any other cerebral structure. CONCLUSIONS These results suggest that the hippocampus is selectively affected by early ethanol exposure and by polyamine synthesis inhibition. In addition, the results suggest a role for polyamines in the long-lasting increase of protein carbonyls induced by ethanol exposure and withdrawal.
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Affiliation(s)
- Carlos Fernando Mello
- Departamento de Fisiologia e Farmacologia, Universidade Federal de Santa Maria, Santa Maria, Brazil
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Allen GC, Farnell YZ, Maeng JU, West JR, Chen WJA, Earnest DJ. Long-term effects of neonatal alcohol exposure on photic reentrainment and phase-shifting responses of the activity rhythm in adult rats. Alcohol 2005; 37:79-88. [PMID: 16584971 PMCID: PMC2695981 DOI: 10.1016/j.alcohol.2005.11.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2005] [Revised: 11/08/2005] [Accepted: 11/18/2005] [Indexed: 11/24/2022]
Abstract
In rats, neonatal alcohol (EtOH) exposure coinciding with the period of rapid brain growth produces structural damage in some brain regions that often persists into adulthood and thus may have long-term consequences in the neural regulation of behavior. Because recent findings indicate that the circadian clock located in the rat suprachiasmatic nucleus is vulnerable to alcohol-induced insults during development, the present study examined the long-term effects of neonatal alcohol exposure on the photic regulation of circadian behavior in adult rats. Rat pups were exposed to alcohol (3.0, 4.5, or 6.0 g x kg(-1) x day(-1)) or isocaloric milk formula on postnatal days 4-9 using artificial-rearing methods. At 2 months of age, animals were housed individually and circadian wheel-running behavior was continuously analyzed to determine the effects of neonatal alcohol treatment on the rate of reentrainment to a 6-h advance in the 12-h light:12-h dark photoperiod and the phase-shifting properties of free-running rhythms in response to discrete light pulses on a background of constant darkness. For all doses, neonatal alcohol exposure had a significant effect in reducing the time for reentrainment such that EtOH-treated rats required four to five fewer days than control animals for stable realignment of the activity rhythm to the shifted light-dark cycle. Coupled with the accelerated rate of reentrainment, the amplitude of light-evoked phase delays at circadian time 14 and advances at circadian time 22 in the 4.5 and 6.0 g x kg(-1) x day(-1) EtOH groups was almost twofold greater than that observed in control animals. The present observations indicate that the mechanisms by which photic signals regulate circadian behavior are permanently altered following alcohol exposure during the period of rapid brain development. These long-term alterations in the photic regulation of circadian rhythms may account, at least partially, for some neurobehavioral consequences of prenatal alcohol exposure in humans such as depression.
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Affiliation(s)
- Gregg C Allen
- Department of Human Anatomy and Medical Neurobiology, The Texas A&M University System Health Science Center, College of Medicine, 228 Reynolds Medical Building, College Station, TX 77843-1114, USA
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Medina AE, Ramoa AS. Early alcohol exposure impairs ocular dominance plasticity throughout the critical period. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2005; 157:107-11. [PMID: 15939092 DOI: 10.1016/j.devbrainres.2005.03.012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2005] [Revised: 03/23/2005] [Accepted: 03/27/2005] [Indexed: 11/20/2022]
Abstract
Animal models of fetal alcohol syndrome (FAS) have revealed an impairment of sensory neocortex plasticity. Here, we examine whether early alcohol exposure leads to a permanent impairment of ocular dominance plasticity (OD) or to an alteration in the timing of the critical period. Ferrets were exposed to alcohol during a brief period of development prior to eye opening and effects of monocular deprivation examined during early, mid and late critical period. Single-unit electrophysiology revealed markedly reduced OD plasticity at every age examined. This finding provides evidence that early alcohol exposure does not affect the timing or duration of the critical period of OD plasticity and suggests an enduring impairment of neural plasticity in FAS.
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Affiliation(s)
- Alexandre E Medina
- Department of Anatomy and Neurobiology, Virginia Commonwealth University School of Medicine, 1101 E Marshall Street, Sanger Hall Room 12-042, Richmond, VA 23298-0709, USA.
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Farnell YZ, West JR, Chen WJA, Allen GC, Earnest DJ. Developmental alcohol exposure alters light-induced phase shifts of the circadian activity rhythm in rats. Alcohol Clin Exp Res 2005; 28:1020-7. [PMID: 15252288 PMCID: PMC2695982 DOI: 10.1097/01.alc.0000130807.21020.1b] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND Developmental alcohol (EtOH) exposure produces long-term changes in the photic regulation of rat circadian behavior. Because entrainment of circadian rhythms to 24-hr light/dark cycles is mediated by phase shifting or resetting the clock mechanism, we examined whether developmental EtOH exposure also alters the phase-shifting effects of light pulses on the rat activity rhythm. METHODS Artificially reared Sprague-Dawley rat pups were exposed to EtOH (4.5 g/kg/day) or an isocaloric milk formula (gastrostomy control; GC) on postnatal days 4 to 9. At 2 months of age, rats from the EtOH, GC, and suckle control groups were housed individually, and wheel-running behavior was continuously recorded first in a 12-hr light/12-hr dark photoperiod for 10 to 14 days and thereafter in constant darkness (DD). Once the activity rhythm was observed to stably free-run in DD for at least 14 days, animals were exposed to a 15-min light pulse at either 2 or 10 hr after the onset of activity [i.e., circadian time (CT) 14 or 22, respectively], because light exposure at these times induces maximal phase delays or advances of the rat activity rhythm. RESULTS EtOH-treated rats were distinguished by robust increases in their phase-shifting responses to light. In the suckle control and GC groups, light pulses shifted the activity rhythm as expected, inducing phase delays of approximately 2 hr at CT 14 and advances of similar amplitude at CT 22. In contrast, the same light stimulus produced phase delays at CT 14 and advances at CT 22 of longer than 3 hr in EtOH-treated rats. The mean phase delay at CT 14 and advance at CT 22 in EtOH rats were significantly greater (p < 0.05) than the light-induced shifts observed in control animals. CONCLUSIONS The data indicate that developmental EtOH exposure alters the phase-shifting responses of the rat activity rhythm to light. This finding, coupled with changes in the circadian period and light/dark entrainment observed in EtOH-treated rats, suggests that developmental EtOH exposure may permanently alter the clock mechanism in the suprachiasmatic nucleus and its regulation of circadian behavior.
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Affiliation(s)
- Yuhua Z Farnell
- Department of Human Anatomy and Medical Neurobiology, Texas A&M University System Health Science Center, College of Medicine, College Station, Texas 77843-1114, USA
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Nixon K, Hughes PD, Amsel A, Leslie SW. NMDA receptor subunit expression after combined prenatal and postnatal exposure to ethanol. Alcohol Clin Exp Res 2004; 28:105-12. [PMID: 14745308 DOI: 10.1097/01.alc.0000106311.88523.7b] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND The N-methyl-D-aspartate receptor (NMDAR), a subtype of glutamate receptor, is essential for normal neurodevelopment. The brain growth spurt, which is both prenatal and postnatal in the rat, is a time when the brain is especially sensitive to the effects of a teratogen, such as alcohol. Changes in NMDAR function after early perinatal exposure to ethanol (EtOH) may be related to alterations in the expression of secondary subunits. Thus, we investigated the expression of the NR1, NR2A, and NR2B subunits after combined prenatal and postnatal exposure to EtOH. METHODS A binge model was used to administer EtOH (5 g/kg) or isocaloric vehicle to pregnant female rats followed by EtOH (6.2 g/kg) or isocaloric control diet from postnatal days 4 through 9 via an artificial rearing method. Proteins from crude membrane homogenates isolated from cortex and hippocampus at postnatal day 10, 14, or 21 were separated in a standard Western blot procedure. RESULTS The expression of the NR2A subunit of EtOH-exposed pups showed a significant increase at postnatal day 10 in hippocampus compared with diet controls. No significant changes were seen for any other subunit in either region. CONCLUSIONS The up-regulation of NR2A during EtOH withdrawal is consistent with compensatory changes to prolonged inhibition of the NMDAR. These results indicate that postnatal exposure to ethanol produces distinct effects on the NMDAR, which may underlie deficits associated with alcohol-related neurodevelopmental disorder.
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Affiliation(s)
- Kimberly Nixon
- Department of Psychology, Waggoner Center for Alcohol and Addiciton Research, University of Texas, Austin, Texas, USA.
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Abstract
Fetal alcohol syndrome is a major cause of learning and sensory deficits. These disabilities may result from disruption of neocortex development and plasticity. Alcohol exposure during the third trimester equivalent of human gestation may have especially severe and long-lasting consequences on learning and sensory processing, because this is when the functional properties and connectivity of neocortical neurons start to develop. To address this issue, we used the monocular deprivation model of neural plasticity, which shares many common mechanisms with learning. Ferrets were exposed to ethanol (3.5 mg/kg, i.p.) on alternate days for 3 weeks starting on postnatal day (P) 10. Animals were then monocularly deprived at the peak of ocular dominance plasticity after a prolonged alcohol-free period (15-20 d). Quantitative single-unit electrophysiology revealed that alcohol exposure disrupted ocular dominance plasticity while preserving robust visual responses. Moreover, optical imaging of intrinsic signals revealed that the reduction in visual cortex area driven by the deprived eye was much less pronounced in ethanol-treated than in control animals. Alcohol exposure starting at a later age (P20) did not disrupt ocular dominance plasticity, indicating that timing of exposure is crucial for the effects on visual plasticity. In conclusion, alcohol exposure during a brief period of development impairs ocular dominance plasticity at a later age. This model provides a novel approach to investigate the consequences of fetal alcohol exposure and should contribute to elucidate how alcohol disrupts neural plasticity.
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