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DuBois DW, Murchison DA, Mahnke AH, Bang E, Winzer-Serhan U, Griffith WH, Souza KA. Maintenance of optogenetic channel rhodopsin (ChR2) function in aging mice: Implications for pharmacological studies of inhibitory synaptic transmission, quantal content, and calcium homeostasis. Neuropharmacology 2023:109651. [PMID: 37414332 DOI: 10.1016/j.neuropharm.2023.109651] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Revised: 06/23/2023] [Accepted: 07/03/2023] [Indexed: 07/08/2023]
Abstract
Disruption of synaptic function is believed to represent a common pathway contributing to cognitive decline during aging. Optogenetics is a prodigious tool for studying relationships between function and synaptic circuitry but models utilizing viral vectors present limitations. Careful characterization of the functionality of channel rhodopsin in transgenic models is crucial for determining whether they can be used across aging. This includes verifying the light sensitivity of the protein and confirming its ability to generate action potentials in response to light stimulation. We combined in vitro optogenetic methodology and a reduced synaptic preparation of acutely isolated neurons to determine if the ChR2(H134R)-eYFP vGAT mouse model is well-suited for aging studies. We used neurons from young (2-6 mo), middle-aged (10-14 mo) and aged (17-25 mo) bacterial artificial chromosome (BAC) transgenic mouse line with stable expression of the channelrhodopsin-2 (ChR2) variant H134R in GABAergic cell populations. Cellular physiology and calcium dynamics were assessed in basal forebrain (BF) neurons using patch-clamp recording and fura-2 microfluorimetry, alongside 470 nm light stimulation of the transgenic ChR2 channel to characterize a wide array of physiological functions known to decline with age. We found ChR2 expression is functionally maintained across aging, while spontaneous and optically evoked inhibitory postsynaptic currents, and quantal content were decreased. Aged mice also showed an increase in intracellular calcium buffering. These results, which are on par with previous observations, demonstrate that the optogenetic vGAT BAC mouse model is well-suited for investigating age-related changes in calcium signaling and synaptic transmission.
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Affiliation(s)
- Dustin W DuBois
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University School of Medicine, USA
| | - David A Murchison
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University School of Medicine, USA
| | - Amanda H Mahnke
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University School of Medicine, USA
| | - Eunyoung Bang
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University School of Medicine, USA
| | - Ursula Winzer-Serhan
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University School of Medicine, USA
| | - William H Griffith
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University School of Medicine, USA
| | - Karienn A Souza
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University School of Medicine, USA.
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Chaves-Coira I, García-Magro N, Zegarra-Valdivia J, Torres-Alemán I, Núñez Á. Cognitive Deficits in Aging Related to Changes in Basal Forebrain Neuronal Activity. Cells 2023; 12:1477. [PMID: 37296598 PMCID: PMC10252596 DOI: 10.3390/cells12111477] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Revised: 05/22/2023] [Accepted: 05/24/2023] [Indexed: 06/12/2023] Open
Abstract
Aging is a physiological process accompanied by a decline in cognitive performance. The cholinergic neurons of the basal forebrain provide projections to the cortex that are directly engaged in many cognitive processes in mammals. In addition, basal forebrain neurons contribute to the generation of different rhythms in the EEG along the sleep/wakefulness cycle. The aim of this review is to provide an overview of recent advances grouped around the changes in basal forebrain activity during healthy aging. Elucidating the underlying mechanisms of brain function and their decline is especially relevant in today's society as an increasingly aged population faces higher risks of developing neurodegenerative diseases such as Alzheimer's disease. The profound age-related cognitive deficits and neurodegenerative diseases associated with basal forebrain dysfunction highlight the importance of investigating the aging of this brain region.
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Affiliation(s)
- Irene Chaves-Coira
- Department of Anatomy, Histology and Neurosciences, Universidad Autónoma de Madrid, 28029 Madrid, Spain;
| | - Nuria García-Magro
- Facultad de Ciencias de la Salud, Universidad Francisco de Vitoria, Pozuelo de Alarcón, 28223 Madrid, Spain;
| | - Jonathan Zegarra-Valdivia
- Achucarro Basque Center for Neuroscience, 48940 Leioa, Spain; (J.Z.-V.); (I.T.-A.)
- Facultad de Ciencias de la Salud, Universidad Señor de Sipán, Chiclayo 02001, Peru
| | - Ignacio Torres-Alemán
- Achucarro Basque Center for Neuroscience, 48940 Leioa, Spain; (J.Z.-V.); (I.T.-A.)
- Ikerbasque Science Foundation, 48009 Bilbao, Spain
| | - Ángel Núñez
- Department of Anatomy, Histology and Neurosciences, Universidad Autónoma de Madrid, 28029 Madrid, Spain;
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3
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Somera B, Frick M, Fadel JR. Age-related changes in basal forebrain afferent activation in response to food paired stimuli. Neurosci Lett 2023; 802:137155. [PMID: 36842481 PMCID: PMC10155118 DOI: 10.1016/j.neulet.2023.137155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 02/21/2023] [Accepted: 02/22/2023] [Indexed: 02/28/2023]
Abstract
The basal forebrain contains a phenotypically-diverse assembly of neurons, including those using acetylcholine as their neurotransmitter. This basal forebrain cholinergic system projects to the entire neocortical mantle as well as subcortical limbic structures that include the hippocampus and amygdala. Basal forebrain pathology, including cholinergic dysfunction, is thought to underlie the cognitive impairments associated with several age-related neurodegenerative conditions, including Alzheimer's disease. Basal forebrain dysfunction may stem, in part, from a failure of normal afferent regulation of cholinergic and other neurons in this area. However, little is understood regarding how aging, alone, affects the functional regulation of basal forebrain afferents in the context of motivated behavior. Here, we used neuronal tract-tracing combined with motivationally salient stimuli in an aged rodent model to examine how aging alters activity in basal forebrain inputs arising from several cortical, limbic and brainstem structures. Young rats showed greater stimulus-associated activation of basal forebrain inputs arising from prelimbic cortex, nucleus accumbens and the ventral tegmental area compared with aged rats. Aged rats also showed increased latency to respond to palatable food presentation compared to young animals. Changes in activation of intrinsic basal forebrain cell populations or afferents were also observed as a function of age or experimental condition. These data further demonstrate that age-related changes in basal forebrain activation and related behavioral and cognitive functions reflect a failure of afferent regulation of this important brain region.
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Affiliation(s)
- Brandy Somera
- Pharmacology, Physiology and Neuroscience, University of South Carolina School of Medicine, Columbia, SC, United States
| | - Marla Frick
- Pharmacology, Physiology and Neuroscience, University of South Carolina School of Medicine, Columbia, SC, United States
| | - Jim R Fadel
- Pharmacology, Physiology and Neuroscience, University of South Carolina School of Medicine, Columbia, SC, United States.
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Zhu L, Hassan SH, Gao X, Johnson JQ, Wang Y, Bregy MV, Wei Z, Chen J, Li P, Stetler RA. Neuron-targeted Knockout of APE1 Forces Premature Cognitive Impairment and Synaptic Dysfunction in Adult Mice. Aging Dis 2022; 13:1862-1874. [PMID: 36465182 PMCID: PMC9662274 DOI: 10.14336/ad.2022.0331] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Accepted: 03/31/2022] [Indexed: 08/02/2023] Open
Abstract
Adaptable and consistent neural function relies at least in part on the ongoing repair of oxidative damage that can accumulate in the brain over a lifespan. To determine whether forebrain neuron-targeted knockout of AP endonuclease 1 (APE1), a critical enzyme in the base excision DNA repair pathway, contributes to neuronal impairments, we generated APE1 conditional knockout mice under the control of the CamKIIα promotor (APE1 cKO). Spatial learning and memory were tested using the Morris water maze. Synaptic markers, including synapsin, vGLUT, GABA1, and GAD were immunostained and quantified. Dendritic morphology and number were characterized using Golgi staining. Long-term potentiation (LTP) was measured in slices from the 6-month-old brain. APE1 cKO mice did not significantly differ from WT mice in the learning phase of the Morris water maze, but performed significantly worse during the memory phase of the Morris water maze. vGLUT, GABA1, and GAD immunostaining was significantly decreased in APE1 cKO mice without concomitant changes in the number of synapsin-positive structures, suggesting that neural networks may be impaired but not at the level of total presynaptic structures. Dendrites were reduced both in number and length of spines in APE1 cKO mice. APE1 cKO brain slices exhibited decreased LTP induction compared to WT brain slices. Together, these data indicate that the conditional loss of APE1 in forebrain neurons leads to a phenotype consistent with expedited brain aging.
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Affiliation(s)
- Ling Zhu
- 1Pittsburgh Institute of Brain Disorder & Recovery and Department of Neurology University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - Sulaiman H Hassan
- 1Pittsburgh Institute of Brain Disorder & Recovery and Department of Neurology University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
- 2Geriatric Research, Education and Clinical Center, Veterans Affairs Pittsburgh Health Care System, Pittsburgh, PA 15261, USA
| | - Xuguang Gao
- 1Pittsburgh Institute of Brain Disorder & Recovery and Department of Neurology University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - Joycelyn Q Johnson
- 1Pittsburgh Institute of Brain Disorder & Recovery and Department of Neurology University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - Yangfan Wang
- 1Pittsburgh Institute of Brain Disorder & Recovery and Department of Neurology University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - M Victoria Bregy
- 1Pittsburgh Institute of Brain Disorder & Recovery and Department of Neurology University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - Zhishuo Wei
- 1Pittsburgh Institute of Brain Disorder & Recovery and Department of Neurology University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - Jun Chen
- 1Pittsburgh Institute of Brain Disorder & Recovery and Department of Neurology University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
- 2Geriatric Research, Education and Clinical Center, Veterans Affairs Pittsburgh Health Care System, Pittsburgh, PA 15261, USA
| | - Peiying Li
- 1Pittsburgh Institute of Brain Disorder & Recovery and Department of Neurology University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - R Anne Stetler
- 1Pittsburgh Institute of Brain Disorder & Recovery and Department of Neurology University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
- 2Geriatric Research, Education and Clinical Center, Veterans Affairs Pittsburgh Health Care System, Pittsburgh, PA 15261, USA
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Huffels CFM, van Dijk RE, Karst H, Meye FJ, Hol EM, Middeldorp J. Systemic Injection of Aged Blood Plasma in Adult C57BL/6 Mice Induces Neurophysiological Impairments in the Hippocampal CA1. J Alzheimers Dis 2022; 89:283-297. [PMID: 35871343 DOI: 10.3233/jad-220337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Aging is characterized by systemic alterations and forms an important risk factor for Alzheimer's disease. Recently, it has been indicated that blood-borne factors present in the systemic milieu contribute to the aging process. Exposing young mice to aged blood plasma results in impaired neurogenesis and synaptic plasticity in the dentate gyrus, as well as impaired cognition. Vice versa, treating aged mice with young blood plasma rescues impairments associated with aging. OBJECTIVE Whether blood-borne factors are sufficient to drive impairments outside the dentate gyrus, how they impact neurophysiology, and how the functional outcome compares to impairments found in mouse models for AD is still unclear. METHODS Here, we treated adult mice with blood plasma from aged mice and assessed neurophysiological parameters in the hippocampal CA1. RESULTS Mice treated with aged blood plasma show significantly impaired levels of long-term potentiation (LTP), similar to those present in APP/PS1 mice. These impaired levels of LTP in plasma-treated mice are associated with alterations in basic properties of glutamatergic transmission and the enhanced activity of voltage-gated Ca2 + channels. CONCLUSION Together, the data presented in this study show that blood-borne factors are sufficient to drive neurophysiological impairments in the hippocampal CA1.
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Affiliation(s)
- Christiaan F M Huffels
- Department of Translational Neuroscience, University Medical Center Utrecht Brain Center, Utrecht University, Utrecht, The Netherlands
| | - Roland E van Dijk
- Department of Translational Neuroscience, University Medical Center Utrecht Brain Center, Utrecht University, Utrecht, The Netherlands
| | - Henk Karst
- Department of Translational Neuroscience, University Medical Center Utrecht Brain Center, Utrecht University, Utrecht, The Netherlands
| | - Frank J Meye
- Department of Translational Neuroscience, University Medical Center Utrecht Brain Center, Utrecht University, Utrecht, The Netherlands
| | - Elly M Hol
- Department of Translational Neuroscience, University Medical Center Utrecht Brain Center, Utrecht University, Utrecht, The Netherlands
| | - Jinte Middeldorp
- Department of Translational Neuroscience, University Medical Center Utrecht Brain Center, Utrecht University, Utrecht, The Netherlands.,Department of Neurobiology & Aging, Biomedical Primate Research Centre, Rijswijk, The Netherlands
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Bang E, Tobery A, Montgomery KS, Fincher AS, Earnest DJ, Murchison DA, Griffith WH. Amitriptyline Decreases GABAergic Transmission in Basal Forebrain Neurons Using an Optogenetic Model of Aging. Front Aging Neurosci 2021; 13:673155. [PMID: 34122049 PMCID: PMC8193944 DOI: 10.3389/fnagi.2021.673155] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Accepted: 04/30/2021] [Indexed: 11/13/2022] Open
Abstract
The antidepressant drug amitriptyline is used in the treatment of clinical depression and a variety of neurological conditions such as anxiety, neuropathic pain disorders and migraine. Antidepressants are associated with both therapeutic and untoward effects, and their use in the elderly has tripled since the mid-1990s. Because of this widespread use, we are interested in testing the acute effects of amitriptyline on synaptic transmission at therapeutic concentrations well below those that block voltage-gated calcium channels. We found that 3 μM amitriptyline reduced the frequency of spontaneous GABAergic inhibitory postsynaptic currents (IPSCs) and reduced quantal content in mice at ages of 7-10 mo. and 23-25 mo., suggesting a presynaptic mechanism of action that does not diminish with age. We employed a reduced synaptic preparation of the basal forebrain (BF) and a new optogenetic aging model utilizing a bacterial artificial chromosome (BAC) transgenic mouse line with stable expression of the channelrhodopsin-2 (ChR2) variant H134R specific for GABAergic neurons [VGAT-ChR2(H134R)-EYFP]. This model enables optogenetic light stimulation of specific GABAergic synaptic terminals across aging. Age-related impairment of circadian behavior was used to confirm predictable age-related changes associated with this model. Our results suggest that low concentrations of amitriptyline act presynaptically to reduce neurotransmitter release and that this action is maintained during aging.
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Affiliation(s)
| | | | | | | | | | | | - William H. Griffith
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University Health Science Center, Bryan, TX, United States
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Damborsky JC, Yakel JL. Regulation of hippocamposeptal input within the medial septum/diagonal band of Broca. Neuropharmacology 2021; 191:108589. [PMID: 33933476 DOI: 10.1016/j.neuropharm.2021.108589] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 04/21/2021] [Accepted: 04/25/2021] [Indexed: 11/19/2022]
Abstract
The medial septum/diagonal band of Broca (MS/DBB) receives direct GABAergic input from the hippocampus via hippocamposeptal (HS) projection neurons as part of a reciprocal loop that mediates cognition and is altered in Alzheimer's disease. Cholinergic and GABAergic interactions occur throughout the MS/DBB, but it is not known how HS GABA release is impacted by these circuits. Most HS neurons contain somatostatin (SST), so to evoke HS GABA release we expressed Cre-dependent mCherry/channelrhodopisin-2 (ChR2) in the hippocampi of SST-IRES-Cre mice and then used optogenetics to stimulate HS fibers while performing whole-cell patch clamp recordings from MS/DBB neurons in acute slices. We found that the acetylcholine receptor (AChR) agonist carbachol and the GABAB receptor (GABABR) agonist baclofen significantly decreased HS GABA release in the MS/DBB. Carbachol's effects were blocked by eliminating local GABAergic activity or inhibiting GABABRs, indicating that it was indirectly decreasing HS GABA release by increasing GABAergic tone. There was no effect of acute exposure to amyloid-β on HS GABA release. Repetitive stimulation of HS fibers increased spontaneous GABA release in the MS/DBB, revealing that HS projections can modulate local GABAergic tone. These results show that HS GABA release has far-reaching impacts on overall levels of inhibition in the MS/DBB and is under regulatory control by cholinergic and GABAergic activity. This bidirectional modulation of GABA release from local and HS projections in the MS/DBB will likely have profound impact not only on activity within the MS/DBB, but also on output to the hippocampus and hippocampal-dependent learning and memory.
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Affiliation(s)
- Joanne C Damborsky
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, 111 TW Alexander Dr., Research Triangle Park, NC, 27709, USA
| | - Jerrel L Yakel
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, 111 TW Alexander Dr., Research Triangle Park, NC, 27709, USA.
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8
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Di Benedetto G, Iannucci LF, Surdo NC, Zanin S, Conca F, Grisan F, Gerbino A, Lefkimmiatis K. Compartmentalized Signaling in Aging and Neurodegeneration. Cells 2021; 10:464. [PMID: 33671541 PMCID: PMC7926881 DOI: 10.3390/cells10020464] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 02/16/2021] [Accepted: 02/17/2021] [Indexed: 12/12/2022] Open
Abstract
The cyclic AMP (cAMP) signalling cascade is necessary for cell homeostasis and plays important roles in many processes. This is particularly relevant during ageing and age-related diseases, where drastic changes, generally decreases, in cAMP levels have been associated with the progressive decline in overall cell function and, eventually, the loss of cellular integrity. The functional relevance of reduced cAMP is clearly supported by the finding that increases in cAMP levels can reverse some of the effects of ageing. Nevertheless, despite these observations, the molecular mechanisms underlying the dysregulation of cAMP signalling in ageing are not well understood. Compartmentalization is widely accepted as the modality through which cAMP achieves its functional specificity; therefore, it is important to understand whether and how this mechanism is affected during ageing and to define which is its contribution to this process. Several animal models demonstrate the importance of specific cAMP signalling components in ageing, however, how age-related changes in each of these elements affect the compartmentalization of the cAMP pathway is largely unknown. In this review, we explore the connection of single components of the cAMP signalling cascade to ageing and age-related diseases whilst elaborating the literature in the context of cAMP signalling compartmentalization.
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Affiliation(s)
- Giulietta Di Benedetto
- Neuroscience Institute, National Research Council of Italy (CNR), 35121 Padova, Italy;
- Veneto Institute of Molecular Medicine, Foundation for Advanced Biomedical Research, 35129 Padova, Italy; (L.F.I.); (S.Z.); (F.C.); (F.G.)
| | - Liliana F. Iannucci
- Veneto Institute of Molecular Medicine, Foundation for Advanced Biomedical Research, 35129 Padova, Italy; (L.F.I.); (S.Z.); (F.C.); (F.G.)
- Department of Molecular Medicine, University of Pavia, 27100 Pavia, Italy
| | - Nicoletta C. Surdo
- Neuroscience Institute, National Research Council of Italy (CNR), 35121 Padova, Italy;
- Veneto Institute of Molecular Medicine, Foundation for Advanced Biomedical Research, 35129 Padova, Italy; (L.F.I.); (S.Z.); (F.C.); (F.G.)
| | - Sofia Zanin
- Veneto Institute of Molecular Medicine, Foundation for Advanced Biomedical Research, 35129 Padova, Italy; (L.F.I.); (S.Z.); (F.C.); (F.G.)
- Department of Molecular Medicine, University of Pavia, 27100 Pavia, Italy
| | - Filippo Conca
- Veneto Institute of Molecular Medicine, Foundation for Advanced Biomedical Research, 35129 Padova, Italy; (L.F.I.); (S.Z.); (F.C.); (F.G.)
- Department of Biology, University of Padova, 35122 Padova, Italy
| | - Francesca Grisan
- Veneto Institute of Molecular Medicine, Foundation for Advanced Biomedical Research, 35129 Padova, Italy; (L.F.I.); (S.Z.); (F.C.); (F.G.)
- Department of Biology, University of Padova, 35122 Padova, Italy
| | - Andrea Gerbino
- Department of Biosciences, Biotechnology and Biopharmaceutics, University of Bari, 70121 Bari, Italy;
| | - Konstantinos Lefkimmiatis
- Veneto Institute of Molecular Medicine, Foundation for Advanced Biomedical Research, 35129 Padova, Italy; (L.F.I.); (S.Z.); (F.C.); (F.G.)
- Department of Molecular Medicine, University of Pavia, 27100 Pavia, Italy
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Structural and Functional Synaptic Plasticity Induced by Convergent Synapse Loss in the Drosophila Neuromuscular Circuit. J Neurosci 2021; 41:1401-1417. [PMID: 33402422 DOI: 10.1523/jneurosci.1492-20.2020] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 11/28/2020] [Accepted: 12/17/2020] [Indexed: 12/22/2022] Open
Abstract
Throughout the nervous system, the convergence of two or more presynaptic inputs on a target cell is commonly observed. The question we ask here is to what extent converging inputs influence each other's structural and functional synaptic plasticity. In complex circuits, isolating individual inputs is difficult because postsynaptic cells can receive thousands of inputs. An ideal model to address this question is the Drosophila larval neuromuscular junction (NMJ) where each postsynaptic muscle cell receives inputs from two glutamatergic types of motor neurons (MNs), known as 1b and 1s MNs. Notably, each muscle is unique and receives input from a different combination of 1b and 1s MNs; we surveyed multiple muscles for this reason. Here, we identified a cell-specific promoter that allows ablation of 1s MNs postinnervation and measured structural and functional responses of convergent 1b NMJs using microscopy and electrophysiology. For all muscles examined in both sexes, ablation of 1s MNs resulted in NMJ expansion and increased spontaneous neurotransmitter release at corresponding 1b NMJs. This demonstrates that 1b NMJs can compensate for the loss of convergent 1s MNs. However, only a subset of 1b NMJs showed compensatory evoked neurotransmission, suggesting target-specific plasticity. Silencing 1s MNs led to similar plasticity at 1b NMJs, suggesting that evoked neurotransmission from 1s MNs contributes to 1b synaptic plasticity. Finally, we genetically blocked 1s innervation in male larvae and robust 1b synaptic plasticity was eliminated, raising the possibility that 1s NMJ formation is required to set up a reference for subsequent synaptic perturbations.SIGNIFICANCE STATEMENT In complex neural circuits, multiple convergent inputs contribute to the activity of the target cell, but whether synaptic plasticity exists among these inputs has not been thoroughly explored. In this study, we examined synaptic plasticity in the structurally and functionally tractable Drosophila larval neuromuscular system. In this convergent circuit, each muscle is innervated by a unique pair of motor neurons. Removal of one neuron after innervation causes the adjacent neuron to increase neuromuscular junction outgrowth and functional output. However, this is not a general feature as each motor neuron differentially compensates. Further, robust compensation requires initial coinnervation by both neurons. Understanding how neurons respond to perturbations in adjacent neurons will provide insight into nervous system plasticity in both healthy and disease states.
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10
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The differential impact of acute microglia activation on the excitability of cholinergic neurons in the mouse medial septum. Brain Struct Funct 2019; 224:2297-2309. [DOI: 10.1007/s00429-019-01905-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Accepted: 06/07/2019] [Indexed: 12/30/2022]
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11
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Montgomery KS, Bancroft EA, Fincher AS, Migut EA, Provasek V, Murchison D, DuBois DW. Effects of ethanol and varenicline on female Sprague-Dawley rats in a third trimester model of fetal alcohol syndrome. Alcohol 2018; 71:75-87. [PMID: 30059955 PMCID: PMC6223131 DOI: 10.1016/j.alcohol.2018.02.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Revised: 02/03/2018] [Accepted: 02/26/2018] [Indexed: 12/17/2022]
Abstract
Perinatal ethanol exposure disrupts a variety of developmental processes in neurons important for establishing a healthy brain. These ethanol-induced impairments known as fetal alcohol spectrum disorder (FASD) are not fully understood, and currently, there is no effective treatment. Further, growing evidence suggests that adult females are more susceptible to ethanol, with the effects of perinatal ethanol exposure also being sexually divergent. Female models have been historically underutilized in neurophysiological investigations, but here, we used a third-trimester binge-ethanol model of FASD to examine changes to basal forebrain (BF) physiology and behavior in female Sprague-Dawley rats. We also tested varenicline as a potential cholinomimetic therapeutic. Rat pups were gavage-treated with binge-like ethanol, varenicline and ethanol, and varenicline alone. Using patch-clamp electrophysiology in BF slices, we observed that binge-ethanol exposure increased spontaneous post-synaptic current (sPSC) frequency. Varenicline exposure alone also enhanced sPSC frequency. Varenicline plus ethanol co-treatment prevented the sPSC frequency increase. Changes in BF synaptic transmission persisted into adolescence after binge-ethanol treatment. Behaviorally, binge-ethanol treated females displayed increased anxiety (thigmotaxis) and demonstrated learning deficits in the water maze. Varenicline/ethanol co-treatment was effective at reducing these behavioral deficits. In the open field, ethanol-treated rats displayed longer distances traveled and spent less time in the center of the open field box. Co-treated rats displayed less anxiety, demonstrating a possible effect of varenicline on this measure. In conclusion, ethanol-induced changes in both BF synaptic transmission and behavior were reduced by varenicline in female rats, supporting a role for cholinergic therapeutics in FASD treatment.
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Affiliation(s)
- Karienn S Montgomery
- Department of Neuroscience and Experimental Therapeutics, Texas A&M Health Science Center, Bryan, TX, United States
| | - Eric A Bancroft
- Department of Neuroscience and Experimental Therapeutics, Texas A&M Health Science Center, Bryan, TX, United States
| | - Annette S Fincher
- Department of Neuroscience and Experimental Therapeutics, Texas A&M Health Science Center, Bryan, TX, United States
| | - Ewelina A Migut
- Department of Neuroscience and Experimental Therapeutics, Texas A&M Health Science Center, Bryan, TX, United States
| | - Vincent Provasek
- Department of Neuroscience and Experimental Therapeutics, Texas A&M Health Science Center, Bryan, TX, United States
| | - David Murchison
- Department of Neuroscience and Experimental Therapeutics, Texas A&M Health Science Center, Bryan, TX, United States
| | - Dustin W DuBois
- Department of Neuroscience and Experimental Therapeutics, Texas A&M Health Science Center, Bryan, TX, United States.
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12
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Hernandez AR, Reasor JE, Truckenbrod LM, Lubke KN, Johnson SA, Bizon JL, Maurer AP, Burke SN. Medial prefrontal-perirhinal cortical communication is necessary for flexible response selection. Neurobiol Learn Mem 2016; 137:36-47. [PMID: 27815215 DOI: 10.1016/j.nlm.2016.10.012] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Revised: 10/20/2016] [Accepted: 10/24/2016] [Indexed: 10/20/2022]
Abstract
The ability to use information from the physical world to update behavioral strategies is critical for survival across species. The prefrontal cortex (PFC) supports behavioral flexibility; however, exactly how this brain structure interacts with sensory association cortical areas to facilitate the adaptation of response selection remains unknown. Given the role of the perirhinal cortex (PER) in higher-order perception and associative memory, the current study evaluated whether PFC-PER circuits are critical for the ability to perform biconditional object discriminations when the rule for selecting the rewarded object shifted depending on the animal's spatial location in a 2-arm maze. Following acquisition to criterion performance on an object-place paired association task, pharmacological blockade of communication between the PFC and PER significantly disrupted performance. Specifically, the PFC-PER disconnection caused rats to regress to a response bias of selecting an object on a particular side regardless of its identity. Importantly, the PFC-PER disconnection did not interfere with the capacity to perform object-only or location-only discriminations, which do not require the animal to update a response rule across trials. These findings are consistent with a critical role for PFC-PER circuits in rule shifting and the effective updating of a response rule across spatial locations.
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Affiliation(s)
- Abbi R Hernandez
- McKnight Brain Institute, Department of Neuroscience, University of Florida, United States
| | - Jordan E Reasor
- McKnight Brain Institute, Department of Neuroscience, University of Florida, United States
| | - Leah M Truckenbrod
- McKnight Brain Institute, Department of Neuroscience, University of Florida, United States
| | - Katelyn N Lubke
- McKnight Brain Institute, Department of Neuroscience, University of Florida, United States; Department of Biomedical Engineering, University of Florida, United States
| | - Sarah A Johnson
- McKnight Brain Institute, Department of Neuroscience, University of Florida, United States
| | - Jennifer L Bizon
- McKnight Brain Institute, Department of Neuroscience, University of Florida, United States
| | - Andrew P Maurer
- McKnight Brain Institute, Department of Neuroscience, University of Florida, United States; Department of Biomedical Engineering, University of Florida, United States
| | - Sara N Burke
- McKnight Brain Institute, Department of Neuroscience, University of Florida, United States; Institute on Aging, University of Florida, United States
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13
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Local cholinergic-GABAergic circuitry within the basal forebrain is modulated by galanin. Brain Struct Funct 2016; 222:1385-1400. [PMID: 27496091 DOI: 10.1007/s00429-016-1283-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 07/26/2016] [Indexed: 02/07/2023]
Abstract
The basal forebrain (BF) is an important regulator of hippocampal and cortical activity. In Alzheimer's disease (AD), there is a significant loss and dysfunction of cholinergic neurons within the BF, and also a hypertrophy of fibers containing the neuropeptide galanin. Understanding how galanin interacts with BF circuitry is critical in determining what role galanin overexpression plays in the progression of AD. Here, we examined the location and function of galanin in the medial septum/diagonal band (MS/DBB) region of the BF. We show that galanin fibers are located throughout the MS/DBB and intermingled with both cholinergic and GABAergic neurons. Whole-cell patch clamp recordings from MS/DBB neurons in acute slices reveal that galanin decreases tetrodotoxin-sensitive spontaneous GABA release and dampens muscarinic receptor-mediated increases in GABA release in the MS/DBB. These effects are not blocked by pre-exposure to β-amyloid peptide (Aβ1-42). Optogenetic activation of cholinergic neurons in the MS/DBB increases GABA release back onto cholinergic neurons, forming a functional circuit within the MS/DBB. Galanin disrupts this cholinergic-GABAergic circuit by blocking the cholinergic-induced increase in GABA release. These data suggest that galanin works in the BF to reduce inhibitory input onto cholinergic neurons and to prevent cholinergic-induced increase in inhibitory tone. This disinhibition of cholinergic neurons could serve as a compensatory mechanism to counteract the loss of cholinergic signaling that occurs during the progression of AD.
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14
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Jackson PA, Forster JS, Bell JG, Dick JR, Younger I, Kennedy DO. DHA Supplementation Alone or in Combination with Other Nutrients Does not Modulate Cerebral Hemodynamics or Cognitive Function in Healthy Older Adults. Nutrients 2016; 8:86. [PMID: 26867200 PMCID: PMC4772049 DOI: 10.3390/nu8020086] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Revised: 01/25/2016] [Accepted: 02/02/2016] [Indexed: 12/25/2022] Open
Abstract
A number of recent trials have demonstrated positive effects of dietary supplementation with the omega-3 polyunsaturated fatty acids (n-3 PUFAs), docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) on measures of cognitive function in healthy young and older adults. One potential mechanism by which EPA, and DHA in particular, may exert these effects is via modulation of cerebral hemodynamics. In order to investigate the effects of DHA alone or provided as one component of a multinutrient supplement (also including Gingko biloba, phosphatidylserine and vitamins B₉ and B₁₂) on measures of cerebral hemodynamics and cognitive function, 86 healthy older adults aged 50-70 years who reported subjective memory deficits were recruited to take part in a six month daily dietary supplementation trial. Relative changes in the concentration of oxygenated hemoglobin and deoxygenated hemoglobin were assessed using Near Infrared Spectroscopy (NIRS) during the performance of cognitive tasks prior to and following the intervention period. Performance on the cognitive tasks was also assessed. No effect of either active treatment was found for any of the NIRS measures or on the cognitive performance tasks, although the study was limited by a number of factors. Further work should continue to evaluate more holistic approaches to cognitive aging.
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Affiliation(s)
- Philippa A Jackson
- Brain, Performance and Nutrition Research Centre, Northumbria University, Newcastle-upon-Tyne NE1 8ST, UK.
| | - Joanne S Forster
- Brain, Performance and Nutrition Research Centre, Northumbria University, Newcastle-upon-Tyne NE1 8ST, UK.
| | - J Gordon Bell
- Institute of Aquaculture, University of Stirling, Stirlingshire FK9 4LA, UK.
| | - James R Dick
- Institute of Aquaculture, University of Stirling, Stirlingshire FK9 4LA, UK.
| | - Irene Younger
- Institute of Aquaculture, University of Stirling, Stirlingshire FK9 4LA, UK.
| | - David O Kennedy
- Brain, Performance and Nutrition Research Centre, Northumbria University, Newcastle-upon-Tyne NE1 8ST, UK.
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15
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Krivova NA, Zaeva OB, Grigorieva VA. Effect of a water-maze procedure on the redox mechanisms in brain parts of aged rats. Front Aging Neurosci 2015; 7:29. [PMID: 25814952 PMCID: PMC4356083 DOI: 10.3389/fnagi.2015.00029] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 02/23/2015] [Indexed: 11/13/2022] Open
Abstract
The Morris water maze (MWM) is a tool for assessment of age-related modulations spatial learning and memory in laboratory rats. In our work was investigated the age-related decline of MWM performance in 11-month-old rats and the effect exerted by training in the MWM on the redox mechanisms in rat brain parts. Young adult (3-month-old) and aged (11-month-old) male rats were trained in the MWM. Intact animals of the corresponding age were used as the reference groups. The level of pro- and antioxidant capacity in brain tissue homogenates was assessed using the chemiluminescence method. A reduced performance in the MWM test was found in 11-month-old rats: at the first day of training they showed only 30% of successful MWM trials. However, at the last training day the percentage of successful trials was equal for young adult and aged animals. This indicates that the aged 11-month-old rats can successfully learn in MWM. Therewith, the MWM spatial learning procedure itself produces changes in different processes of redox homeostasis in 11-month-old and 3-month-old rats as compared to intact animals. Young adult rats showed a decrease in prooxidant capacity in all brain parts, while 11-month-old rats demonstrated an increase in antioxidant capacity in the olfactory bulb, pons + medulla oblongata and frontal lobe cortex. Hence, the MWM procedure activates the mechanisms that restrict the oxidative stress in brain parts. The obtained results may be an argument for further development of the animal training procedures aimed to activate the mechanisms that can prevent the age-related deterioration of performance in the learning test. This may be useful not only for the development of training procedures applicable to human patients with age-related cognitive impairments, but also for their rehabilitation.
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Affiliation(s)
- Natalia A Krivova
- Laboratory of Experimental Physiology, Institute of Biology and Biophysics, Tomsk State University Tomsk, Russia
| | - Olga B Zaeva
- Laboratory of Experimental Physiology, Institute of Biology and Biophysics, Tomsk State University Tomsk, Russia
| | - Valery A Grigorieva
- Laboratory of Experimental Physiology, Institute of Biology and Biophysics, Tomsk State University Tomsk, Russia
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