1
|
Zhang W, Liu T, Li J, Singh J, Chan A, Islam A, Petrache A, Peng Y, Harvey K, Ali AB. Decreased extrasynaptic δ-GABA A receptors in PNN-associated parvalbumin interneurons correlates with anxiety in APP and tau mouse models of Alzheimer's disease. Br J Pharmacol 2024. [PMID: 38886118 DOI: 10.1111/bph.16441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2024] [Revised: 05/02/2024] [Accepted: 05/06/2024] [Indexed: 06/20/2024] Open
Abstract
BACKGROUND Alzheimer's disease (AD) is associated with gradual memory loss and anxiety which affects ~75% of AD patients. This study investigated whether AD-associated anxiety correlated with modulation of extrasynaptic δ-subunit-containing GABAA receptors (δ-GABAARs) in experimental mouse models of AD. EXPERIMENTAL APPROACH We combined behavioural experimental paradigms to measure cognition performance, and anxiety with neuroanatomy and molecular biology, using familial knock-in (KI) mouse models of AD that harbour β-amyloid (Aβ) precursor protein App (AppNL-F) with or without humanized microtubule-associated protein tau (MAPT), age-matched to wild-type control mice at three different age windows. RESULTS AppNL-F KI and AppNL-F/MAPT AD models showed a similar magnitude of cognitive decline and elevated magnitude of anxiety correlated with neuroinflammatory hallmarks, including triggering receptor expressed on myeloid cells 2 (TREM2), reactive astrocytes and activated microglia consistent with accumulation of Aβ, tau and down-regulation of Wnt/β-catenin signalling compared to aged-matched WT controls. In both the CA1 region of the hippocampus and dentate gyrus, there was an age-dependent decline in the expression of δ-GABAARs selectively expressed in parvalbumin (PV)-expressing interneurons, encapsulated by perineuronal nets (PNNs) in the AD mouse models compared to WT mice. In vivo positive allosteric modulation of the δ-GABAARs, using a δ-selective-compound DS2, decreased the level of anxiety in the AD mouse models, which was correlated with reduced hallmarks of neuroinflammation, and 'normalisation' of the expression of δ-GABAARs. CONCLUSIONS Our data show that the δ-GABAARs could potentially be targeted for alleviating symptoms of anxiety, which would greatly improve the quality of life of AD individuals.
Collapse
|
2
|
Alshakhouri M, Sharpe C, Bergin P, Sumner RL. Female sex steroids and epilepsy: Part 1. A review of reciprocal changes in reproductive systems, cycles, and seizures. Epilepsia 2024; 65:556-568. [PMID: 38036939 DOI: 10.1111/epi.17842] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 11/27/2023] [Accepted: 11/28/2023] [Indexed: 12/02/2023]
Abstract
Seizures, antiseizure medications, and the reproductive systems are reciprocally entwined. In Section 2 of this review, we outline how seizures may affect the hypothalamic-pituitary-gonadal axis, thereby altering sex steroids, and changes in sex steroids across the menstrual cycle and changes in pharmacokinetics during pregnancy may alter seizure susceptibility. The literature indicates that females with epilepsy experience increased rates of menstrual disturbances and reproductive endocrine disorders. The latter include polycystic ovary syndrome, especially for females on valproate. Studies of fertility have yielded mixed results. We aim to summarize and attempt to detangle the existing knowledge on these reciprocal interactions. The menstrual cycle causes changes in seizure intensity and frequency for many females. When this occurs perimenstrually, during ovulation, or in association with an inadequate luteal phase, it is termed catamenial epilepsy. There is a clear biophysiological rationale for how the key female reproductive neurosteroids interact with the brain to alter the seizure threshold, and Section 3 outlines this important relationship. Critically, what remains unknown is the specific pathophysiology of catamenial epilepsy that describes why not all females are affected. There is a need for mechanism-focused investigations in humans to uncover the complexity of the relationship between reproductive hormones, menstrual cycles, and the brain.
Collapse
Affiliation(s)
| | - Cynthia Sharpe
- Department of Paediatric Neurology, Starship Children's Health, Auckland, New Zealand
| | - Peter Bergin
- Neurology Auckland Hospital, Te Whatu Ora, Auckland, New Zealand
| | - Rachael L Sumner
- School of Pharmacy, University of Auckland, Auckland, New Zealand
| |
Collapse
|
3
|
Wei X, Campagna JJ, Jagodzinska B, Wi D, Cohn W, Lee J, Zhu C, Huang CS, Molnár L, Houser CR, John V, Mody I. A therapeutic small molecule lead enhances γ-oscillations and improves cognition/memory in Alzheimer's disease model mice. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.04.569994. [PMID: 38106006 PMCID: PMC10723366 DOI: 10.1101/2023.12.04.569994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
Brain rhythms provide the timing and concurrence of brain activity required for linking together neuronal ensembles engaged in specific tasks. In particular, the γ-oscillations (30-120 Hz) orchestrate neuronal circuits underlying cognitive processes and working memory. These oscillations are reduced in numerous neurological and psychiatric disorders, including early cognitive decline in Alzheimer's disease (AD). Here we report on a potent brain permeable small molecule, DDL-920 that increases γ-oscillations and improves cognition/memory in a mouse model of AD, thus showing promise as a new class of therapeutics for AD. As a first in CNS pharmacotherapy, our lead candidate acts as a potent, efficacious, and selective negative allosteric modulator (NAM) of the γ-aminobutyric acid type A receptors (GABA A Rs) assembled from α1β2δ subunits. We identified these receptors through anatomical and pharmacological means to mediate the tonic inhibition of parvalbumin (PV) expressing interneurons (PV+INs) critically involved in the generation of γ-oscillations. Our approach is unique as it is meant to enhance cognitive performance and working memory in a state-dependent manner by engaging and amplifying the brain's endogenous γ-oscillations through enhancing the function of PV+INs.
Collapse
|
4
|
Jing J, Hu M, Ngodup T, Ma Q, Lau SNN, Ljungberg C, McGinley MJ, Trussell LO, Jiang X. Comprehensive analysis of cellular specializations that initiate parallel auditory processing pathways in mice. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.15.539065. [PMID: 37293040 PMCID: PMC10245571 DOI: 10.1101/2023.05.15.539065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The cochlear nuclear complex (CN) is the starting point for all central auditory processing and comprises a suite of neuronal cell types that are highly specialized for neural coding of acoustic signals. To examine how their striking functional specializations are determined at the molecular level, we performed single-nucleus RNA sequencing of the mouse CN to molecularly define all constituent cell types and related them to morphologically- and electrophysiologically-defined neurons using Patch-seq. We reveal an expanded set of molecular cell types encompassing all previously described major types and discover new subtypes both in terms of topographic and cell-physiologic properties. Our results define a complete cell-type taxonomy in CN that reconciles anatomical position, morphological, physiological, and molecular criteria. This high-resolution account of cellular heterogeneity and specializations from the molecular to the circuit level illustrates molecular underpinnings of functional specializations and enables genetic dissection of auditory processing and hearing disorders with unprecedented specificity.
Collapse
Affiliation(s)
- Junzhan Jing
- Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital, Houston, TX, USA
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Ming Hu
- Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital, Houston, TX, USA
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Tenzin Ngodup
- Oregon Hearing Research Center and Vollum Institute, Oregon Health and Science University, Portland, OR, USA
| | - Qianqian Ma
- Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital, Houston, TX, USA
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Shu-Ning Natalie Lau
- Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital, Houston, TX, USA
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Cecilia Ljungberg
- Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital, Houston, TX, USA
- Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA
| | - Matthew J. McGinley
- Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital, Houston, TX, USA
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Laurence O. Trussell
- Oregon Hearing Research Center and Vollum Institute, Oregon Health and Science University, Portland, OR, USA
| | - Xiaolong Jiang
- Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital, Houston, TX, USA
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX, USA
| |
Collapse
|
5
|
Mohamad FH, Mohamad Jamali MA, Che Has AT. Structure-function Studies of GABA (A) Receptors and Related computer-aided Studies. J Mol Neurosci 2023; 73:804-817. [PMID: 37750966 DOI: 10.1007/s12031-023-02158-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Accepted: 09/12/2023] [Indexed: 09/27/2023]
Abstract
The γ-aminobutyric acid type A receptor (GABA (A) receptor) is a membrane protein activated by the neurotransmitter GABA. Structurally, this major inhibitory neurotransmitter receptor in the human central nervous system is a pentamer that can be built from a selection of 19 subunits consisting of α(1,2,3,4,5 or 6), β (1,2 or 3), γ (1,2 or 3), ρ (1,2 or 3), and δ, π, θ, and ε. This creates several possible pentameric arrangements, which also influence the pharmacological and physiological properties of the receptor. The complexity and heterogeneity of the receptors are further increased by the addition of short and long splice variants in several subunits and the existence of multiple allosteric binding sites and expansive ligands that can bind to the receptors. Therefore, a comprehensive understanding of the structure and function of the receptors is required to gain novel insights into the consequences of receptor dysfunction and subsequent drug development studies. Notably, advancements in computational-aided studies have facilitated the elucidation of residual interactions and exploring energy binding, which may otherwise be challenging to investigate. In this review, we aim to summarize the current understanding of the structure and function of GABA (A) receptors obtained from advancements in computational-aided applications.
Collapse
Affiliation(s)
- Fatin H Mohamad
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Health Campus, Kubang Kerian, 16150 Kota Bharu, Kelantan, Malaysia
| | - Muhamad Arif Mohamad Jamali
- Faculty of Science and Technology, Universiti Sains Islam Malaysia, Bandar Baru Nilai, 71800, Nilai, Negeri Sembilan, Malaysia
| | - Ahmad Tarmizi Che Has
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Health Campus, Kubang Kerian, 16150 Kota Bharu, Kelantan, Malaysia.
| |
Collapse
|
6
|
Nardi L, Chhabra S, Leukel P, Krueger-Burg D, Sommer CJ, Schmeisser MJ. Neuroanatomical changes of ionotropic glutamatergic and GABAergic receptor densities in male mice modeling idiopathic and syndromic autism spectrum disorder. Front Psychiatry 2023; 14:1199097. [PMID: 37547211 PMCID: PMC10401048 DOI: 10.3389/fpsyt.2023.1199097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2023] [Accepted: 06/29/2023] [Indexed: 08/08/2023] Open
Abstract
Autism spectrum disorder (ASD) comprises a wide range of neurodevelopment conditions primarily characterized by impaired social interaction and repetitive behavior, accompanied by a variable degree of neuropsychiatric characteristics. Synaptic dysfunction is undertaken as one of the key underlying mechanisms in understanding the pathophysiology of ASD. The excitatory/inhibitory (E/I) hypothesis is one of the most widely held theories for its pathogenesis. Shifts in E/I balance have been proven in several ASD models. In this study, we investigated three mouse lines recapitulating both idiopathic (the BTBR strain) and genetic (Fmr1 and Shank3 mutants) forms of ASD at late infancy and early adulthood. Using receptor autoradiography for ionotropic excitatory (AMPA and NMDA) and inhibitory (GABAA) receptors, we mapped the receptor binding densities in brain regions known to be associated with ASD such as prefrontal cortex, dorsal and ventral striatum, dorsal hippocampus, and cerebellum. The individual mouse lines investigated show specific alterations in excitatory ionotropic receptor density, which might be accounted as specific hallmark of each individual line. Across all the models investigated, we found an increased binding density to GABAA receptors at adulthood in the dorsal hippocampus. Interestingly, reduction in the GABAA receptor binding density was observed in the cerebellum. Altogether, our findings suggest that E/I disbalance individually affects several brain regions in ASD mouse models and that alterations in GABAergic transmission might be accounted as unifying factor.
Collapse
Affiliation(s)
- Leonardo Nardi
- Institute of Anatomy, University Medical Center of the Johannes Gutenberg-University, Mainz, Germany
| | - Stuti Chhabra
- Institute of Anatomy, University Medical Center of the Johannes Gutenberg-University, Mainz, Germany
- Focus Program Translational Neurosciences, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Petra Leukel
- Institute of Neuropathology, University Medical Center of the Johannes Gutenberg-University, Mainz, Germany
| | - Dilja Krueger-Burg
- Institute of Anatomy, University Medical Center of the Johannes Gutenberg-University, Mainz, Germany
- Focus Program Translational Neurosciences, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Clemens J. Sommer
- Focus Program Translational Neurosciences, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
- Institute of Neuropathology, University Medical Center of the Johannes Gutenberg-University, Mainz, Germany
| | - Michael J. Schmeisser
- Institute of Anatomy, University Medical Center of the Johannes Gutenberg-University, Mainz, Germany
- Focus Program Translational Neurosciences, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
| |
Collapse
|
7
|
Dalziel JE, Zobel G, Dewhurst H, Hurst C, Olson T, Rodriguez-Sanchez R, Mace L, Parkar N, Thum C, Hannaford R, Fraser K, MacGibbon A, Bassett SA, Dekker J, Anderson RC, Young W. A Diet Enriched with Lacticaseibacillus rhamnosus HN001 and Milk Fat Globule Membrane Alters the Gut Microbiota and Decreases Amygdala GABA a Receptor Expression in Stress-Sensitive Rats. Int J Mol Sci 2023; 24:10433. [PMID: 37445611 DOI: 10.3390/ijms241310433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2023] [Revised: 06/12/2023] [Accepted: 06/19/2023] [Indexed: 07/15/2023] Open
Abstract
Brain signalling pathways involved in subclinical anxiety and depressed mood can be modulated via the gut brain axis (GBA), providing the potential for diet and dietary components to affect mood. We investigated behavioural, physiological and gut microbiome responses to the Lacticaseibacillus rhamnosus strain HN001 (LactoB HN001™), which has been shown to reduce postpartum anxiety and depression, and a milk fat globule membrane-enriched product, Lipid 70 (SurestartTM MFGM Lipid 70), which has been implicated in memory in stress-susceptible Wistar Kyoto rats. We examined behaviour in the open field, elevated plus maze and novel object recognition tests in conjunction with the expression of host genes in neuro-signalling pathways, and we also assessed brain lipidomics. Treatment-induced alterations in the caecal microbiome and short-chain fatty acid (SCFA) profiles were also assessed. Neither ingredient induced behavioural changes or altered the brain lipidome (separately or when combined). However, with regard to brain gene expression, the L. rhamnosus HN001 + Lipid 70 combination produced a synergistic effect, reducing GABAA subunit expression in the amygdala (Gabre, Gat3, Gabrg1) and hippocampus (Gabrd). Treatment with L. rhamnosus HN001 alone altered expression of the metabotropic glutamate receptor (Grm4) in the amygdala but produced only minor changes in gut microbiota composition. In contrast, Lipid 70 alone did not alter brain gene expression but produced a significant shift in the gut microbiota profile. Under the conditions used, there was no observed effect on rat behaviour for the ingredient combination. However, the enhancement of brain gene expression by L. rhamnosus HN001 + Lipid 70 implicates synergistic actions on region-specific neural pathways associated with fear, anxiety, depression and memory. A significant shift in the gut microbiota profile also occurred that was mainly attributable to Lipid 70.
Collapse
Affiliation(s)
- Julie E Dalziel
- Smart Foods & Bioproducts, AgResearch, Palmerston North 4442, New Zealand
| | - Gosia Zobel
- Ethical Agriculture, AgResearch, Hamilton 3240, New Zealand
| | - Hilary Dewhurst
- Smart Foods & Bioproducts, AgResearch, Palmerston North 4442, New Zealand
| | - Charlotte Hurst
- Smart Foods & Bioproducts, AgResearch, Palmerston North 4442, New Zealand
| | - Trent Olson
- Smart Foods & Bioproducts, AgResearch, Palmerston North 4442, New Zealand
| | | | - Louise Mace
- Smart Foods & Bioproducts, AgResearch, Palmerston North 4442, New Zealand
| | - Nabil Parkar
- Smart Foods & Bioproducts, AgResearch, Palmerston North 4442, New Zealand
| | - Caroline Thum
- Smart Foods & Bioproducts, AgResearch, Palmerston North 4442, New Zealand
| | - Rina Hannaford
- Digital Agriculture, AgResearch, Palmerston North 4442, New Zealand
| | - Karl Fraser
- Smart Foods & Bioproducts, AgResearch, Palmerston North 4442, New Zealand
| | - Alastair MacGibbon
- Fonterra Research and Development Centre Co., Ltd., Palmerston North 4442, New Zealand
| | - Shalome A Bassett
- Fonterra Research and Development Centre Co., Ltd., Palmerston North 4442, New Zealand
| | - James Dekker
- Fonterra Research and Development Centre Co., Ltd., Palmerston North 4442, New Zealand
| | - Rachel C Anderson
- Smart Foods & Bioproducts, AgResearch, Palmerston North 4442, New Zealand
| | - Wayne Young
- Smart Foods & Bioproducts, AgResearch, Palmerston North 4442, New Zealand
| |
Collapse
|
8
|
Schmiedhofer P, Vogel FD, Koniuszewski F, Ernst M. Cys-loop receptors on cannabinoids: All high? Front Physiol 2022; 13:1044575. [PMID: 36439263 PMCID: PMC9682269 DOI: 10.3389/fphys.2022.1044575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Accepted: 10/24/2022] [Indexed: 11/10/2022] Open
Abstract
Endocannabinoids (eCBS) are endogenously derived lipid signaling molecules that serve as tissue hormones and interact with multiple targets, mostly within the endocannabinoid system (ECS). The ECS is a highly conserved regulatory system involved in homeostatic regulation, organ formation, and immunomodulation of chordates. The term “cannabinoid” evolved from the distinctive class of plant compounds found in Cannabis sativa, an ancient herb, due to their action on CB1 and CB2 receptors. CB1/2 receptors are the primary targets for eCBs, but their effects are not limited to the ECS. Due to the high interest and extensive research on the ECS, knowledge on its constituents and physiological role is substantial and still growing. Crosstalk and multiple targeting of molecules are common features of endogenous and plant compounds. Cannabimimetic molecules can be divided according to their origin, natural or synthetic, including phytocannabinoids (pCB’s) or synthetic cannabinoids (sCB’s). The endocannabinoid system (ECS) consists of receptors, transporters, enzymes, and signaling molecules. In this review, we focus on the effects of cannabinoids on Cys-loop receptors. Cys-loop receptors belong to the class of membrane-bound pentameric ligand gated ion channels, each family comprising multiple subunits. Mammalians possess GABA type A receptors (GABAAR), glycine receptors (GlyR), serotonin receptors type 3 (5-HT3R), and nicotinic acetylcholine receptors (nAChR). Several studies have shown different modulatory effects of CBs on multiple members of the Cys-loop receptor family. We highlight the existing knowledge, especially on subunits and protein domains with conserved binding sites for CBs and their possible pharmacological and physiological role in epilepsy and in chronic pain. We further discuss the potential for cannabinoids as first line treatments in epilepsy, chronic pain and other neuropsychiatric conditions, indicated by their polypharmacology and therapeutic profile.
Collapse
Affiliation(s)
- Philip Schmiedhofer
- SBR Development Holding, Vienna, Austria
- *Correspondence: Philip Schmiedhofer, ; Margot Ernst,
| | - Florian Daniel Vogel
- Department of Pathobiology of the Nervous System, Center for Brain Research, Medical University Vienna, Vienna, Austria
| | - Filip Koniuszewski
- Department of Pathobiology of the Nervous System, Center for Brain Research, Medical University Vienna, Vienna, Austria
| | - Margot Ernst
- Department of Pathobiology of the Nervous System, Center for Brain Research, Medical University Vienna, Vienna, Austria
- *Correspondence: Philip Schmiedhofer, ; Margot Ernst,
| |
Collapse
|
9
|
Bakalar D, O’Reilly JJ, Lacaille H, Salzbank J, Ellegood J, Lerch JP, Sasaki T, Imamura Y, Hashimoto-Torii K, Vacher CM, Penn AA. Lack of placental neurosteroid alters cortical development and female somatosensory function. Front Endocrinol (Lausanne) 2022; 13:972033. [PMID: 36313771 PMCID: PMC9606442 DOI: 10.3389/fendo.2022.972033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Accepted: 09/28/2022] [Indexed: 01/24/2023] Open
Abstract
Placental endocrine function is essential to fetal brain development. Placental hormones include neurosteroids such as allopregnanolone (ALLO), a regulator of neurodevelopmental processes via positive allosteric modulation of the GABAA receptor (GABAA-R). Using a mouse model (plKO) in which the gene encoding the ALLO synthesis enzyme is specifically deleted in trophoblasts, we previously showed that placental ALLO insufficiency alters cerebellar white matter development and leads to male-specific autistic-like behavior. We now demonstrate that the lack of placental ALLO causes female-predominant alterations of cortical development and function. Placental ALLO insufficiency disrupts cell proliferation in the primary somatosensory cortex (S1) in a sex-linked manner. Early changes are seen in plKO embryos of both sexes, but persist primarily in female offspring after birth. Adolescent plKO females show significant reduction in pyramidal neuron density, as well as somatosensory behavioral deficits as compared with plKO males and control littermates. Assessment of layer-specific markers in human postmortem cortices suggests that preterm infants may also have female-biased abnormalities in cortical layer specification as compared with term infants. This study establishes a novel and fundamental link between placental function and sex-linked long-term neurological outcomes, emphasizing the importance of the growing field of neuroplacentology.
Collapse
Affiliation(s)
- Dana Bakalar
- Center for Neuroscience Research, Children’s Research Institute, Children’s National Health System, Washington, DC, United States
| | - Jiaqi J. O’Reilly
- Division of Neonatology, Department of Pediatrics, NewYork-Presbyterian Morgan Stanley Children’s Hospital, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, United States
| | - Helene Lacaille
- Division of Neonatology, Department of Pediatrics, NewYork-Presbyterian Morgan Stanley Children’s Hospital, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, United States
| | - Jacquelyn Salzbank
- Division of Neonatology, Department of Pediatrics, NewYork-Presbyterian Morgan Stanley Children’s Hospital, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, United States
| | - Jacob Ellegood
- Mouse Imaging Centre (MICe), Hospital for Sick Children, Toronto, ON, Canada
| | - Jason P. Lerch
- Wellcome Centre for Integrative Neuroimaging (WIN), Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, United Kingdom
| | - Toru Sasaki
- Center for Neuroscience Research, Children’s Research Institute, Children’s National Health System, Washington, DC, United States
| | - Yuka Imamura
- Department of Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine, Hershey, PA, United States
| | - Kazue Hashimoto-Torii
- Center for Neuroscience Research, Children’s Research Institute, Children’s National Health System, Washington, DC, United States
| | - Claire-Marie Vacher
- Division of Neonatology, Department of Pediatrics, NewYork-Presbyterian Morgan Stanley Children’s Hospital, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, United States
| | - Anna A. Penn
- Division of Neonatology, Department of Pediatrics, NewYork-Presbyterian Morgan Stanley Children’s Hospital, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, United States
| |
Collapse
|
10
|
Michalettos G, Ruscher K. Crosstalk Between GABAergic Neurotransmission and Inflammatory Cascades in the Post-ischemic Brain: Relevance for Stroke Recovery. Front Cell Neurosci 2022; 16:807911. [PMID: 35401118 PMCID: PMC8983863 DOI: 10.3389/fncel.2022.807911] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 02/28/2022] [Indexed: 11/28/2022] Open
Abstract
Adaptive plasticity processes are required involving neurons as well as non-neuronal cells to recover lost brain functions after an ischemic stroke. Recent studies show that gamma-Aminobutyric acid (GABA) has profound effects on glial and immune cell functions in addition to its inhibitory actions on neuronal circuits in the post-ischemic brain. Here, we provide an overview of how GABAergic neurotransmission changes during the first weeks after stroke and how GABA affects functions of astroglial and microglial cells as well as peripheral immune cell populations accumulating in the ischemic territory and brain regions remote to the lesion. Moreover, we will summarize recent studies providing data on the immunomodulatory actions of GABA of relevance for stroke recovery. Interestingly, the activation of GABA receptors on immune cells exerts a downregulation of detrimental anti-inflammatory cascades. Conversely, we will discuss studies addressing how specific inflammatory cascades affect GABAergic neurotransmission on the level of GABA receptor composition, GABA synthesis, and release. In particular, the chemokines CXCR4 and CX3CR1 pathways have been demonstrated to modulate receptor composition and synthesis. Together, the actual view on the interactions between GABAergic neurotransmission and inflammatory cascades points towards a specific crosstalk in the post-ischemic brain. Similar to what has been shown in experimental models, specific therapeutic modulation of GABAergic neurotransmission and inflammatory pathways may synergistically promote neuronal plasticity to enhance stroke recovery.
Collapse
Affiliation(s)
- Georgios Michalettos
- Laboratory for Experimental Brain Research, Division of Neurosurgery, Department of Clinical Sciences, Wallenberg Neuroscience Center, Lund University, Lund, Sweden
| | - Karsten Ruscher
- Laboratory for Experimental Brain Research, Division of Neurosurgery, Department of Clinical Sciences, Wallenberg Neuroscience Center, Lund University, Lund, Sweden
- LUBIN Lab—Lunds Laboratorium för Neurokirurgisk Hjärnskadeforskning, Division of Neurosurgery, Department of Clinical Sciences, Lund University, Lund, Sweden
- *Correspondence: Karsten Ruscher
| |
Collapse
|
11
|
Lambert PM, Lu X, Zorumski CF, Mennerick S. Physiological markers of rapid antidepressant effects of allopregnanolone. J Neuroendocrinol 2022; 34:e13023. [PMID: 34423498 PMCID: PMC8807818 DOI: 10.1111/jne.13023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/29/2021] [Revised: 07/28/2021] [Accepted: 07/29/2021] [Indexed: 02/04/2023]
Abstract
The rise of ketamine and brexanolone as rapid antidepressant treatments raises the question of common mechanisms. Both drugs act without the long onset time of traditional antidepressants such as selective serotonin reuptake inhibitors. The drugs also share the interesting feature of benefit that persists beyond the initial drug lifetime. Here, we briefly review literature on functional changes that may mark the triggering mechanism of rapid antidepressant actions. Because ketamine has a longer history of study as a rapid antidepressant, we use this literature as a template to guide hypotheses about common action. Brexanolone has the complication of being a formulation of a naturally occurring neurosteroid; thus, endogenous levels need to be considered when studying the impact of exogenous administration. We conclude that network disinhibition and increased high-frequency oscillations are candidates to mediate acute triggering effects of rapid antidepressants.
Collapse
Affiliation(s)
- Peter M Lambert
- Department of Psychiatry, Washington University in St Louis School of Medicine, St Louis, MO, USA
| | - Xinguo Lu
- Department of Psychiatry, Washington University in St Louis School of Medicine, St Louis, MO, USA
| | - Charles F Zorumski
- Department of Psychiatry, Washington University in St Louis School of Medicine, St Louis, MO, USA
- Taylor Family Institute for Innovative Psychiatric Research, Washington University in St Louis School of Medicine, St Louis, MO, USA
| | - Steven Mennerick
- Department of Psychiatry, Washington University in St Louis School of Medicine, St Louis, MO, USA
- Taylor Family Institute for Innovative Psychiatric Research, Washington University in St Louis School of Medicine, St Louis, MO, USA
| |
Collapse
|
12
|
Bavo F, de-Jong H, Petersen J, Falk-Petersen CB, Löffler R, Sparrow E, Rostrup F, Eliasen JN, Wilhelmsen KS, Barslund K, Bundgaard C, Nielsen B, Kristiansen U, Wellendorph P, Bogdanov Y, Frølund B. Structure-Activity Studies of 3,9-Diazaspiro[5.5]undecane-Based γ-Aminobutyric Acid Type A Receptor Antagonists with Immunomodulatory Effect. J Med Chem 2021; 64:17795-17812. [PMID: 34908407 DOI: 10.1021/acs.jmedchem.1c00290] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The 3,9-diazaspiro[5.5]undecane-based compounds 2027 and 018 have previously been reported to be potent competitive γ-aminobutyric acid type A receptor (GABAAR) antagonists showing low cellular membrane permeability. Given the emerging peripheral application of GABAAR ligands, we hypothesize 2027 analogs as promising lead structures for peripheral GABAAR inhibition. We herein report a study on the structural determinants of 2027 in order to suggest a potential binding mode as a basis for rational design. The study identified the importance of the spirocyclic benzamide, compensating for the conventional acidic moiety, for GABAAR ligands. The structurally simplified m-methylphenyl analog 1e displayed binding affinity in the high-nanomolar range (Ki = 180 nM) and was superior to 2027 and 018 regarding selectivity for the extrasynaptic α4βδ subtype versus the α1- and α2- containing subtypes. Importantly, 1e was shown to efficiently rescue inhibition of T cell proliferation, providing a platform to explore the immunomodulatory potential for this class of compounds.
Collapse
Affiliation(s)
- Francesco Bavo
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark
| | - Heleen de-Jong
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark
| | - Jonas Petersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark
| | - Christina Birkedahl Falk-Petersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark
| | - Rebekka Löffler
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark
| | - Emma Sparrow
- Antibody and Vaccine Group, Centre for Cancer Immunology, MP127, University of Southampton Faculty of Medicine, Southampton, Hants SO16 6YD, United Kingdom
| | - Frederik Rostrup
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark
| | - Jannik Nicklas Eliasen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark
| | - Kristine S Wilhelmsen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark
| | - Kasper Barslund
- Translational DMPK, H. Lundbeck A/S, Ottiliavej 9, 2500 Valby, Denmark
| | | | - Birgitte Nielsen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark
| | - Uffe Kristiansen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark
| | - Petrine Wellendorph
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark
| | - Yury Bogdanov
- Antibody and Vaccine Group, Centre for Cancer Immunology, MP127, University of Southampton Faculty of Medicine, Southampton, Hants SO16 6YD, United Kingdom
| | - Bente Frølund
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark
| |
Collapse
|
13
|
Sueviriyapan N, Granados-Fuentes D, Simon T, Herzog ED, Henson MA. Modelling the functional roles of synaptic and extra-synaptic γ-aminobutyric acid receptor dynamics in circadian timekeeping. J R Soc Interface 2021; 18:20210454. [PMID: 34520693 PMCID: PMC8440032 DOI: 10.1098/rsif.2021.0454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Accepted: 08/23/2021] [Indexed: 11/12/2022] Open
Abstract
In the suprachiasmatic nucleus (SCN), γ-aminobutyric acid (GABA) is a primary neurotransmitter. GABA can signal through two types of GABAA receptor subunits, often referred to as synaptic GABAA (gamma subunit) and extra-synaptic GABAA (delta subunit). To test the functional roles of these distinct GABAA in regulating circadian rhythms, we developed a multicellular SCN model where we could separately compare the effects of manipulating GABA neurotransmitter or receptor dynamics. Our model predicted that blocking GABA signalling modestly increased synchrony among circadian cells, consistent with published SCN pharmacology. Conversely, the model predicted that lowering GABAA receptor density reduced firing rate, circadian cell fraction, amplitude and synchrony among individual neurons. When we tested these predictions, we found that the knockdown of delta GABAA reduced the amplitude and synchrony of clock gene expression among cells in SCN explants. The model further predicted that increasing gamma GABAA densities could enhance synchrony, as opposed to increasing delta GABAA densities. Overall, our model reveals how blocking GABAA receptors can modestly increase synchrony, while increasing the relative density of gamma over delta subunits can dramatically increase synchrony. We hypothesize that increased gamma GABAA density in the winter could underlie the tighter phase relationships among SCN cells.
Collapse
Affiliation(s)
- Natthapong Sueviriyapan
- Department of Chemical Engineering and the Institute for Applied Life Sciences, University of Massachusetts, Amherst, MA, USA
| | | | - Tatiana Simon
- Department of Biology, Washington University in St Louis, Saint Louis, MO, USA
| | - Erik D. Herzog
- Department of Biology, Washington University in St Louis, Saint Louis, MO, USA
| | - Michael A. Henson
- Department of Chemical Engineering and the Institute for Applied Life Sciences, University of Massachusetts, Amherst, MA, USA
| |
Collapse
|
14
|
Copping NA, McTighe SM, Fink KD, Silverman JL. Emerging Gene and Small Molecule Therapies for the Neurodevelopmental Disorder Angelman Syndrome. Neurotherapeutics 2021; 18:1535-1547. [PMID: 34528170 PMCID: PMC8608975 DOI: 10.1007/s13311-021-01082-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/26/2021] [Indexed: 02/07/2023] Open
Abstract
Angelman syndrome (AS) is a rare (~1:15,000) neurodevelopmental disorder characterized by severe developmental delay and intellectual disability, impaired communication skills, and a high prevalence of seizures, sleep disturbances, ataxia, motor deficits, and microcephaly. AS is caused by loss-of-function of the maternally inherited UBE3A gene. UBE3A is located on chromosome 15q11-13 and is biallelically expressed throughout the body but only maternally expressed in the brain due to an RNA antisense transcript that silences the paternal copy. There is currently no cure for AS, but advancements in small molecule drugs and gene therapies offer a promising approach for the treatment of the disorder. Here, we review AS and how loss-of-function of the maternal UBE3A contributes to the disorder. We also discuss the strengths and limitations of current animal models of AS. Furthermore, we examine potential small molecule drug and gene therapies for the treatment of AS and associated challenges faced by the therapeutic design. Finally, gene therapy offers the opportunity for precision medicine in AS and advancements in the treatment of this disorder can serve as a foundation for other single-gene neurodevelopmental disorders.
Collapse
Affiliation(s)
- Nycole A Copping
- School of Medicine, Department of Psychiatry and Behavioral Sciences, MIND Institute, University of California, Research II Building 96, 4625 2nd Avenue, Suite 1001B, Davis, Sacramento, CA, 95817, USA
- Stem Cell Program and Gene Therapy Center, Department of Neurology, MIND Institute, University of California, Davis, Sacramento, CA, USA
| | | | - Kyle D Fink
- Stem Cell Program and Gene Therapy Center, Department of Neurology, MIND Institute, University of California, Davis, Sacramento, CA, USA
| | - Jill L Silverman
- School of Medicine, Department of Psychiatry and Behavioral Sciences, MIND Institute, University of California, Research II Building 96, 4625 2nd Avenue, Suite 1001B, Davis, Sacramento, CA, 95817, USA.
| |
Collapse
|
15
|
Kipnis PA, Kadam SD. Novel Concepts for the Role of Chloride Cotransporters in Refractory Seizures. Aging Dis 2021; 12:1056-1069. [PMID: 34221549 PMCID: PMC8219493 DOI: 10.14336/ad.2021.0129] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2020] [Accepted: 01/29/2021] [Indexed: 12/12/2022] Open
Abstract
Epilepsy is associated with a multitude of acquired or genetic neurological disorders characterized by a predisposition to spontaneous recurrent seizures. An estimated 15 million patients worldwide have ongoing seizures despite optimal management and are classified as having refractory epilepsy. Early-life seizures like those caused by perinatal hypoxic ischemic encephalopathy (HIE) remain a clinical challenge because although transient, they are difficult to treat and associated with poor neurological outcomes. Pediatric epilepsy syndromes are consistently associated with intellectual disability and neurocognitive comorbidities. HIE and arterial ischemic stroke are the most common causes of seizures in term neonates and account for 7.5-20% of neonatal seizures. Standard first-line treatments such as phenobarbital (PB) and phenytoin fail to curb seizures in ~50% of neonates. In the long-term, HIE can result in hippocampal sclerosis and temporal lobe epilepsy (TLE), which is the most common adult epilepsy, ~30% of which is associated with refractory seizures. For patients with refractory TLE seizures, a viable option is the surgical resection of the epileptic foci. Novel insights gained from investigating the developmental role of Cl- cotransporter function have helped to elucidate some of the mechanisms underlying the emergence of refractory seizures in both HIE and TLE. KCC2 as the chief Cl- extruder in neurons is critical for enabling strong hyperpolarizing synaptic inhibition in the brain and has been implicated in the pathophysiology underlying both conditions. More recently, KCC2 function has become a novel therapeutic target to combat refractory seizures.
Collapse
Affiliation(s)
- Pavel A Kipnis
- Neuroscience Laboratory, Hugo Moser Research Institute at Kennedy Krieger, Baltimore, MD 21205, USA.
| | - Shilpa D Kadam
- Neuroscience Laboratory, Hugo Moser Research Institute at Kennedy Krieger, Baltimore, MD 21205, USA.
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
| |
Collapse
|
16
|
Grotell M, Abdurakhmanova S, Elsilä LV, Korpi ER. Mice Lacking GABA A Receptor δ Subunit Have Altered Pharmaco-EEG Responses to Multiple Drugs. Front Pharmacol 2021; 12:706894. [PMID: 34234684 PMCID: PMC8255781 DOI: 10.3389/fphar.2021.706894] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2021] [Accepted: 06/11/2021] [Indexed: 11/13/2022] Open
Abstract
In the brain, extrasynaptically expressed ionotropic, δ subunit-containing γ-aminobutyric acid A-type receptors (δ-GABAARs) have been implicated in drug effects at both neuronal and behavioral levels. These alterations are supposed to be caused via drug-induced modulation of receptor ionophores affecting chloride ion-mediated inhibitory tonic currents. Often, a transgenic mouse model genetically lacking the δ-GABAARs (δ-KO) has been used to study the roles of δ-GABAARs in brain functions, because a specific antagonist of the δ-GABAARs is still lacking. We have previously observed with these δ-KO mice that activation of δ-GABAARs is needed for morphine-induced conditioning of place preference, and others have suggested that δ-GABAARs act as targets selectively for low doses of ethanol. Furthermore, activation of these receptors via drug-mediated agonism induces a robust increase in the slow-wave frequency bands of electroencephalography (EEG). Here, we tested δ-KO mice (compared to littermate wild-type controls) for the pharmaco-EEG responses of a broad spectrum of pharmacologically different drug classes, including alcohol, opioids, stimulants, and psychedelics. Gaboxadol (THIP), a known superagonist of δ-GABAARs, was included as the positive control, and as expected, δ-KO mice produced a blunted pharmaco-EEG response to 6 mg/kg THIP. Pharmaco-EEGs showed notable differences between treatments but also differences between δ-KO mice and their wild-type littermates. Interestingly mephedrone (4-MMC, 5 mg/kg), an amphetamine-like stimulant, had reduced effects in the δ-KO mice. The responses to ethanol (1 g/kg), LSD (0.2 mg/kg), and morphine (20 mg/kg) were similar in δ-KO and wild-type mice. Since stimulants are not known to act on δ-GABAARs, our findings on pharmaco-EEG effects of 4-MMC suggest that δ-GABAARs are involved in the secondary indirect regulation of the brain rhythms after 4-MMC.
Collapse
Affiliation(s)
- Milo Grotell
- Department of Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | | | - Lauri V Elsilä
- Department of Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Esa R Korpi
- Department of Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| |
Collapse
|
17
|
Liao VWY, Chebib M, Ahring PK. Efficient expression of concatenated α1β2δ and α1β3δ GABA A receptors, their pharmacology and stoichiometry. Br J Pharmacol 2021; 178:1556-1573. [PMID: 33491192 DOI: 10.1111/bph.15380] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Revised: 12/28/2020] [Accepted: 01/11/2021] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND AND PURPOSE GABAA receptors containing δ-subunits are notorious for being difficult to study in vitro due to heterogeneity of expressed receptor populations and low GABA-evoked current amplitudes. Thus, there are some published misconceptions and contradictory conclusions made regarding the pharmacology and stoichiometry of δ-containing receptors. The aim of this study was to obtain robust homogenous expression of α1βδ receptors for in-depth investigation. EXPERIMENTAL APPROACH Novel δ-containing pentameric concatenated constructs were designed. The resulting α1β2δ and α1β3δ GABAA receptor concatemers were investigated by two-electrode voltage-clamp electrophysiology using Xenopus laevis oocytes. KEY RESULTS First, while homogenous α1βδ GABAA receptor pools could not be obtained by manipulating the ratio of injected cRNAs of free α1, β2/3, and δ subunits, concatenated pentameric α1β2δ and α1β3δ constructs resulted in robust expression levels of concatemers. Second, by using optimised constructs that give unidirectional assembly of concatemers, we found that the δ subunit cannot directly participate in GABA binding and receptor activation. Hence, functional δ-containing receptors are likely to all have a conventional 2α:2β:1δ stoichiometry arranged as βαβαδ when viewed counterclockwise from the extracellular side. Third, α1β2/3δ receptors were found to express efficiently in X. laevis oocytes but have a low estimated open probability of ~0.5% upon GABA activation. Because of this, these receptors are uniquely susceptible to positive allosteric modulation by, for example, neurosteroids. CONCLUSION AND IMPLICATIONS Our data answer important outstanding questions regarding the pharmacology and stoichiometry of α1δ-containing GABAA receptors and pave the way for future analysis and drug discovery efforts.
Collapse
Affiliation(s)
- Vivian Wan Yu Liao
- Brain and Mind Centre, Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia
| | - Mary Chebib
- Brain and Mind Centre, Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia
| | - Philip Kiaer Ahring
- Brain and Mind Centre, Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia
| |
Collapse
|
18
|
Morrison KE, Cole AB, Kane PJ, Meadows VE, Thompson SM, Bale TL. Pubertal adversity alters chromatin dynamics and stress circuitry in the pregnant brain. Neuropsychopharmacology 2020; 45:1263-1271. [PMID: 32045935 PMCID: PMC7297802 DOI: 10.1038/s41386-020-0634-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Revised: 01/07/2020] [Accepted: 02/03/2020] [Indexed: 01/03/2023]
Abstract
Women who have experienced adverse childhood events (ACEs) around puberty are at the greatest risk for neuropsychiatric disorders across the lifespan. This population is exceptionally vulnerable to neuropsychiatric disease presentation during the hormonally dynamic state of pregnancy. We previously established that chronic adversity around puberty in female mice significantly altered their HPA axis function specifically during pregnancy, modeling the effects of pubertal ACEs we also reported in women. We hypothesized that the pregnancy hormone, allopregnanolone, was involved in presentation of the blunted stress response phenotype by its interaction with the molecular programming that had occurred during pubertal adversity experience. Here, in adult mice previously stressed during puberty, allopregnanolone administration was sufficient to reproduce the decreased corticosterone response after acute stress. Examination of neuronal activation and the electrophysiological properties of CRF neurons in the paraventricular nucleus of the hypothalamus (PVN) found no significant changes in synaptic function that corresponded with the blunted HPA axis reactivity. However, at the chromatin level, utilization of ATAC-Seq profiling demonstrated a dramatic remodeling of DNA accessibility in the PVN following pubertal adversity. Altogether, these data establish a potential molecular mechanism whereby adversity during puberty can enact lasting transcriptional control that manifests only during a unique period of the lifespan where dynamic hormonal changes occur. These results highlight a biological process that may impart an increased risk for a highly vulnerable population, whereby pubertal programming of the PVN results in aberrant HPA axis responsiveness when exposed to the hormonal changes unique to pregnancy.
Collapse
Affiliation(s)
- Kathleen E Morrison
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, MD, USA
- Center for Epigenetic Research in Child Health and Brain Development, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Anthony B Cole
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA
- Program in Neuroscience, Medical Scientist Training Program, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Patrick J Kane
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Victoria E Meadows
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Scott M Thompson
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA
- Department of Psychiatry, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Tracy L Bale
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, MD, USA.
- Center for Epigenetic Research in Child Health and Brain Development, University of Maryland School of Medicine, Baltimore, MD, USA.
- Department of Psychiatry, University of Maryland School of Medicine, Baltimore, MD, USA.
| |
Collapse
|
19
|
Khalyfa A, Sanz-Rubio D. Genetics and Extracellular Vesicles of Pediatrics Sleep Disordered Breathing and Epilepsy. Int J Mol Sci 2019; 20:ijms20215483. [PMID: 31689970 PMCID: PMC6862182 DOI: 10.3390/ijms20215483] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 10/14/2019] [Accepted: 10/28/2019] [Indexed: 12/27/2022] Open
Abstract
Sleep remains one of the least understood phenomena in biology, and sleep disturbances are one of the most common behavioral problems in childhood. The etiology of sleep disorders is complex and involves both genetic and environmental factors. Epilepsy is the most popular childhood neurological condition and is characterized by an enduring predisposition to generate epileptic seizures, and the neurobiological, cognitive, psychological, and social consequences of this condition. Sleep and epilepsy are interrelated, and the importance of sleep in epilepsy is less known. The state of sleep also influences whether a seizure will occur at a given time, and this differs considerably for various epilepsy syndromes. The development of epilepsy has been associated with single or multiple gene variants. The genetics of epilepsy is complex and disorders exhibit significant genetic heterogeneity and variability in the expressivity of seizures. Phenobarbital (PhB) is the most widely used antiepileptic drug. With its principal mechanism of action to prolong the opening time of the γ-aminobutyric acid (GABA)-A receptor-associated chloride channel, it enhances chloride anion influx into neurons, with subsequent hyperpolarization, thereby reducing excitability. Enzymes that metabolize pharmaceuticals including PhB are well known for having genetic polymorphisms that contribute to adverse drug–drug interactions. PhB metabolism is highly dependent upon the cytochrome P450 (CYP450) and genetic polymorphisms can lead to variability in active drug levels. The highly polymorphic CYP2C19 isozymes are responsible for metabolizing a large portion of routinely prescribed drugs and variants contribute significantly to adverse drug reactions and therapeutic failures. A limited number of CYP2C19 single nucleotide polymorphisms (SNPs) are involved in drug metabolism. Extracellular vesicles (EVs) are circular membrane fragments released from the endosomal compartment as exosomes are shed from the surfaces of the membranes of most cell types. Increasing evidence indicated that EVs play a pivotal role in cell-to-cell communication. Theses EVs may play an important role between sleep, epilepsy, and treatments. The discovery of exosomes provides potential strategies for the diagnosis and treatment of many diseases including neurocognitive deficit. The aim of this study is to better understand and provide further knowledge about the metabolism and interactions between phenobarbital and CYP2C19 polymorphisms in children with epilepsy, interplay between sleep, and EVs. Understanding this interplay between epilepsy and sleep is helpful in the optimal treatment of all patients with epileptic seizures. The use of genetics and extracellular vesicles as precision medicine for the diagnosis and treatment of children with sleep disorder will improve the prognosis and the quality of life in patients with epilepsy.
Collapse
Affiliation(s)
- Abdelnaby Khalyfa
- Department of Pediatrics, Section of Sleep Medicine, The University of Chicago, Chicago, IL 60637, USA.
- Department of Child Health and the Child Health Research Institute, University of Missouri School of Medicine, Columbia, MO 65201, USA.
| | - David Sanz-Rubio
- Department of Child Health and the Child Health Research Institute, University of Missouri School of Medicine, Columbia, MO 65201, USA.
| |
Collapse
|
20
|
Kang S, Cox CL, Gulley JM. High frequency stimulation-induced plasticity in the prelimbic cortex of rats emerges during adolescent development and is associated with an increase in dopamine receptor function. Neuropharmacology 2018; 141:158-166. [PMID: 30165079 DOI: 10.1016/j.neuropharm.2018.08.037] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2018] [Revised: 08/13/2018] [Accepted: 08/26/2018] [Indexed: 01/10/2023]
Abstract
Recent studies in rats suggest that high frequency stimulation (HFS) in the ventral hippocampus induces long-term depression (LTD) in the deep layer of the medial prefrontal cortex (mPFC), but only after the prefrontal GABA system has sufficiently developed during early-to mid-adolescence. It is not clear whether this LTD is specific to the hippocampus-mPFC circuit or is instead an intrinsitc regulatory mechanism for the developed mPFC neuro-network. The potential mechanisms underlying this HFS-induced LTD are also largely unknown. In the current study, naïve male Sprague Dawley rats were sacrificed during peri-adolescence or young adulthood for in vitro extracellular recording to determine if HFS delivered in the prelimbic cortex (PLC) would induce LTD in an age-dependent manner and if dopamine receptors are involved in the expression of this LTD. We found four trains of stimulation at 50 Hz induced an LTD in the PFC of adult, but not peri-adolescent, rats. This LTD required intact GABAA receptor functioning and could also be blocked by dopamine D1 or D2 receptor antagonists. Bath application of selective D1 or D2 receptor agonists produced a significant facilitation or suppression in the field potential, respectively, and these effects were only observed in the adult PLC. Furthermore, neither D1 nor D2 stimualtion prior to HFS was able to facilitate LTD in the peri-adolescent PLC. Together, these results suggest dopamine receptor functionality in the PLC increases during adolescent development and it plays an important role in this late-maturating form of plasticity.
Collapse
Affiliation(s)
- Shuo Kang
- Neuroscience Program, University of Illinois, Urbana-Champaign, USA
| | - Charles L Cox
- Neuroscience Program, University of Illinois, Urbana-Champaign, USA; Department of Molecular and Integrative Physiology, University of Illinois, Urbana-Champaign, USA; Department of Pharmacology, University of Illinois, Urbana-Champaign, USA; Beckman Institute for Advanced Science, University of Illinois, Urbana-Champaign, USA.
| | - Joshua M Gulley
- Neuroscience Program, University of Illinois, Urbana-Champaign, USA; Department of Psychology, University of Illinois, Urbana-Champaign, USA; Institute for Genomic Biology, University of Illinois, Urbana-Champaign, USA.
| |
Collapse
|
21
|
Feng HJ, Forman SA. Comparison of αβδ and αβγ GABA A receptors: Allosteric modulation and identification of subunit arrangement by site-selective general anesthetics. Pharmacol Res 2017; 133:289-300. [PMID: 29294355 DOI: 10.1016/j.phrs.2017.12.031] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Revised: 12/28/2017] [Accepted: 12/29/2017] [Indexed: 12/27/2022]
Abstract
GABAA receptors play a dominant role in mediating inhibition in the mature mammalian brain, and defects of GABAergic neurotransmission contribute to the pathogenesis of a variety of neurological and psychiatric disorders. Two types of GABAergic inhibition have been described: αβγ receptors mediate phasic inhibition in response to transient high-concentrations of synaptic GABA release, and αβδ receptors produce tonic inhibitory currents activated by low-concentration extrasynaptic GABA. Both αβδ and αβγ receptors are important targets for general anesthetics, which induce apparently different changes both in GABA-dependent receptor activation and in desensitization in currents mediated by αβγ vs. αβδ receptors. Many of these differences are explained by correcting for the high agonist efficacy of GABA at most αβγ receptors vs. much lower efficacy at αβδ receptors. The stoichiometry and subunit arrangement of recombinant αβγ receptors are well established as β-α-γ-β-α, while those of αβδ receptors remain controversial. Importantly, some potent general anesthetics selectively bind in transmembrane inter-subunit pockets of αβγ receptors: etomidate acts at β+/α- interfaces, and the barbiturate R-5-allyl-1-methyl-5-(m-trifluoromethyl-diazirynylphenyl) barbituric acid (R-mTFD-MPAB) acts at α+/β- and γ+/β- interfaces. Thus, these drugs are useful as structural probes in αβδ receptors formed from free subunits or concatenated subunit assemblies designed to constrain subunit arrangement. Although a definite conclusion cannot be drawn, studies using etomidate and R-mTFD-MPAB support the idea that recombinant α1β3δ receptors may share stoichiometry and subunit arrangement with α1β3γ2 receptors.
Collapse
Affiliation(s)
- Hua-Jun Feng
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, and Department of Anesthesia, Harvard Medical School, Boston, MA 02114, USA.
| | - Stuart A Forman
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, and Department of Anesthesia, Harvard Medical School, Boston, MA 02114, USA.
| |
Collapse
|
22
|
Chuang SH, Reddy DS. Genetic and Molecular Regulation of Extrasynaptic GABA-A Receptors in the Brain: Therapeutic Insights for Epilepsy. J Pharmacol Exp Ther 2017; 364:180-197. [PMID: 29142081 DOI: 10.1124/jpet.117.244673] [Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 11/13/2017] [Indexed: 12/18/2022] Open
Abstract
GABA-A receptors play a pivotal role in many brain diseases. Epilepsy is caused by acquired conditions and genetic defects in GABA receptor channels regulating neuronal excitability in the brain. The latter is referred to as GABA channelopathies. In the last two decades, major advances have been made in the genetics of epilepsy. The presence of specific GABAergic genetic abnormalities leading to some of the classic epileptic syndromes has been identified. Advances in molecular cloning and recombinant systems have helped characterize mutations in GABA-A receptor subunit genes in clinical neurology. GABA-A receptors are the prime targets for neurosteroids (NSs). However, GABA-A receptors are not static but undergo rapid changes in their number or composition in response to the neuroendocrine milieu. This review describes the recent advances in the genetic and neuroendocrine control of extrasynaptic and synaptic GABA-A receptors in epilepsy and its impact on neurologic conditions. It highlights the current knowledge of GABA genetics in epilepsy, with an emphasis on the neuroendocrine regulation of extrasynaptic GABA-A receptors in network excitability and seizure susceptibility. Recent advances in molecular regulation of extrasynaptic GABA-A receptor-mediated tonic inhibition are providing unique new therapeutic approaches for epilepsy, status epilepticus, and certain brain disorders. The discovery of an extrasynaptic molecular mechanism represents a milestone for developing novel therapies such as NS replacement therapy for catamenial epilepsy.
Collapse
Affiliation(s)
- Shu-Hui Chuang
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University Health Science Center, Bryan, Texas
| | - Doodipala Samba Reddy
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University Health Science Center, Bryan, Texas
| |
Collapse
|
23
|
Transcriptomic correlates of neuron electrophysiological diversity. PLoS Comput Biol 2017; 13:e1005814. [PMID: 29069078 PMCID: PMC5673240 DOI: 10.1371/journal.pcbi.1005814] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Revised: 11/06/2017] [Accepted: 10/09/2017] [Indexed: 12/19/2022] Open
Abstract
How neuronal diversity emerges from complex patterns of gene expression remains poorly understood. Here we present an approach to understand electrophysiological diversity through gene expression by integrating pooled- and single-cell transcriptomics with intracellular electrophysiology. Using neuroinformatics methods, we compiled a brain-wide dataset of 34 neuron types with paired gene expression and intrinsic electrophysiological features from publically accessible sources, the largest such collection to date. We identified 420 genes whose expression levels significantly correlated with variability in one or more of 11 physiological parameters. We next trained statistical models to infer cellular features from multivariate gene expression patterns. Such models were predictive of gene-electrophysiological relationships in an independent collection of 12 visual cortex cell types from the Allen Institute, suggesting that these correlations might reflect general principles relating expression patterns to phenotypic diversity across very different cell types. Many associations reported here have the potential to provide new insights into how neurons generate functional diversity, and correlations of ion channel genes like Gabrd and Scn1a (Nav1.1) with resting potential and spiking frequency are consistent with known causal mechanisms. Our work highlights the promise and inherent challenges in using cell type-specific transcriptomics to understand the mechanistic origins of neuronal diversity.
Collapse
|
24
|
Vidal V, García-Cerro S, Martínez P, Corrales A, Lantigua S, Vidal R, Rueda N, Ozmen L, Hernández MC, Martínez-Cué C. Decreasing the Expression of GABA A α5 Subunit-Containing Receptors Partially Improves Cognitive, Electrophysiological, and Morphological Hippocampal Defects in the Ts65Dn Model of Down Syndrome. Mol Neurobiol 2017; 55:4745-4762. [PMID: 28717969 DOI: 10.1007/s12035-017-0675-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Accepted: 06/27/2017] [Indexed: 12/31/2022]
Abstract
Trisomy 21 or Down syndrome (DS) is the most common cause of intellectual disability of a genetic origin. The Ts65Dn (TS) mouse, which is the most commonly used and best-characterized mouse model of DS, displays many of the cognitive, neuromorphological, and biochemical anomalies that are found in the human condition. One of the mechanisms that have been proposed to be responsible for the cognitive deficits in this mouse model is impaired GABA-mediated inhibition. Because of the well-known modulatory role of GABAA α5 subunit-containing receptors in cognitive processes, these receptors are considered to be potential targets for improving the intellectual disability in DS. The chronic administration of GABAA α5-negative allosteric modulators has been shown to be procognitive without anxiogenic or proconvulsant side effects. In the present study, we use a genetic approach to evaluate the contribution of GABAA α5 subunit-containing receptors to the cognitive, electrophysiological, and neuromorphological deficits in TS mice. We show that reducing the expression of GABAA α5 receptors by deleting one or two copies of the Gabra5 gene in TS mice partially ameliorated the cognitive impairments, improved long-term potentiation, enhanced neural differentiation and maturation, and normalized the density of the GABAergic synapse markers. Reducing the gene dosage of Gabra5 in TS mice did not induce motor alterations and anxiety or affect the viability of the mice. Our results provide further evidence of the role of GABAA α5 receptor-mediated inhibition in cognitive impairment in the TS mouse model of DS.
Collapse
Affiliation(s)
- Verónica Vidal
- Departamento de Fisiología y Farmacología, Facultad de Medicina, Universidad deCantabria, Santander, Spain
| | - Susana García-Cerro
- Departamento de Fundamentos Clínicos, Unidad de Farmacología, Universitat de Barcelona, Barcelona, Spain
| | - Paula Martínez
- Departamento de Fisiología y Farmacología, Facultad de Medicina, Universidad deCantabria, Santander, Spain
| | - Andrea Corrales
- Departamento de Fisiología y Farmacología, Facultad de Medicina, Universidad deCantabria, Santander, Spain
| | - Sara Lantigua
- Departamento de Fisiología y Farmacología, Facultad de Medicina, Universidad deCantabria, Santander, Spain
| | - Rebeca Vidal
- Departamento de Fisiología y Farmacología, Facultad de Medicina, Universidad deCantabria, Santander, Spain.,Instituto de Biomedicina y Biotecnología de Cantabria, IBBTEC (Universidad de Cantabria, CSIC, SODERCAN), Santander, Spain.,Centro de Investigacion Biomédica en Red de Salud Mental (CIBERSAM), Instituto de Salud Carlos III, Madrid, Spain
| | - Noemí Rueda
- Departamento de Fisiología y Farmacología, Facultad de Medicina, Universidad deCantabria, Santander, Spain
| | - Laurence Ozmen
- Pharma Research and Early Development, Hoffman-La Roche Ltd., Basel, Switzerland
| | | | - Carmen Martínez-Cué
- Departamento de Fisiología y Farmacología, Facultad de Medicina, Universidad deCantabria, Santander, Spain.
| |
Collapse
|
25
|
Centanni SW, Burnett EJ, Trantham-Davidson H, Chandler LJ. Loss of δ-GABA A receptor-mediated tonic currents in the adult prelimbic cortex following adolescent alcohol exposure. Addict Biol 2017; 22:616-628. [PMID: 26804056 DOI: 10.1111/adb.12353] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Revised: 10/29/2015] [Accepted: 11/24/2015] [Indexed: 11/30/2022]
Abstract
Delayed maturation of the adolescent prefrontal cortex may render it particularly vulnerable to insults, including those associated with drugs of abuse. Using a rat model of binge alcohol exposure, the present study examined the effect of adolescent intermittent ethanol (AIE) exposure during postnatal days 28-42 on γ-aminobutyric acid (GABA)ergic neurotransmission in the prelimbic cortex. In control rats, patch-clamp electrophysiology in acute slices obtained at different postnatal ages revealed a developmental increase in the GABAA receptor-mediated tonic current in layer V pyramidal neurons but no change in layers II/III when measured in the adult. In slices from AIE-exposed rats, the amplitude of the tonic current was significantly reduced compared with controls when tested at postnatal days 45, 60 and 90-120. This AIE-induced reduction in tonic current was found to reflect attenuation of currents mediated by δ-subunit containing receptors. Consistent with this, facilitation of the tonic current by bath application of either ethanol or allopregnanolone was attenuated in slices from AIE-exposed adult rats compared with control rats. However, expression of this facilitation as a percent of the amplitude of the total current mediated by δ-GABAA receptors revealed that AIE did not alter their sensitivity to either agonist. Lastly, immunohistochemistry and Western blot analysis revealed no change in the expression of δ-GABAA subunits or their surface expression. Taken together, these studies reveal that AIE exposure results in persistent deficits in δ-GABAA tonic currents in the adult prelimbic cortex that may contribute to deficits in decision-making and behavioral control in adulthood.
Collapse
Affiliation(s)
- Samuel W. Centanni
- Department of Neuroscience; Medical University of South Carolina; Charleston SC USA
| | - Elizabeth J. Burnett
- Department of Neuroscience; Medical University of South Carolina; Charleston SC USA
| | | | - L. Judson Chandler
- Department of Neuroscience; Medical University of South Carolina; Charleston SC USA
| |
Collapse
|
26
|
Degani-Katzav N, Gortler R, Weissman M, Paas Y. Mutational Analysis at Intersubunit Interfaces of an Anionic Glutamate Receptor Reveals a Key Interaction Important for Channel Gating by Ivermectin. Front Mol Neurosci 2017; 10:92. [PMID: 28428744 PMCID: PMC5382172 DOI: 10.3389/fnmol.2017.00092] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Accepted: 03/17/2017] [Indexed: 11/13/2022] Open
Abstract
The broad-spectrum anthelmintic drug ivermectin (IVM) activates and stabilizes an open-channel conformation of invertebrate chloride-selective glutamate receptors (GluClRs), thereby causing a continuous inflow of chloride ions and sustained membrane hyperpolarization. These effects suppress nervous impulses and vital physiological processes in parasitic nematodes. The GluClRs are pentamers. Homopentameric receptors assembled from the Caenorhabditis elegans (C. elegans) GluClα (GLC-1) subunit can inherently respond to IVM but not to glutamate (the neurotransmitter). In contrast, heteromeric GluClα/β (GLC-1/GLC-2) assemblies respond to both ligands, independently of each other. Glutamate and IVM bind at the interface between adjacent subunits, far away from each other; glutamate in the extracellular ligand-binding domain, and IVM in the ion-channel pore periphery. To understand the importance of putative intersubunit contacts located outside the glutamate and IVM binding sites, we introduced mutations at intersubunit interfaces, between these two binding-site types. Then, we determined the effect of these mutations on the activation of the heteromeric mutant receptors by glutamate and IVM. Amongst these mutations, we characterized an α-subunit point mutation located close to the putative IVM-binding pocket, in the extracellular end of the first transmembrane helix (M1). This mutation (αF276A) moderately reduced the sensitivity of the heteromeric GluClαF276A/βWT receptor to glutamate, and slightly decreased the receptor subunits’ cooperativity in response to glutamate. In contrast, the αF276A mutation drastically reduced the sensitivity of the receptor to IVM and significantly increased the receptor subunits’ cooperativity in response to IVM. We suggest that this mutation reduces the efficacy of channel gating, and impairs the integrity of the IVM-binding pocket, likely by disrupting important interactions between the tip of M1 and the M2-M3 loop of an adjacent subunit. We hypothesize that this physical contact between M1 and the M2-M3 loop tunes the relative orientation of the ion-channel transmembrane helices M1, M2 and M3 to optimize pore opening. Interestingly, pre-exposure of the GluClαF276A/βWT mutant receptor to subthreshold IVM concentration recovered the receptor sensitivity to glutamate. We infer that IVM likely retained its positive modulation activity by constraining the transmembrane helices in a preopen orientation sensitive to glutamate, with no need for the aforementioned disrupted interactions between M1 and the M2-M3 loop.
Collapse
Affiliation(s)
- Nurit Degani-Katzav
- Laboratory of Ion Channels, The Mina and Everard Goodman Faculty of Life Sciences, Institute of Nanotechnology and Advanced Materials, Bar-Ilan UniversityRamat Gan, Israel
| | - Revital Gortler
- Laboratory of Ion Channels, The Mina and Everard Goodman Faculty of Life Sciences, Institute of Nanotechnology and Advanced Materials, Bar-Ilan UniversityRamat Gan, Israel
| | - Marina Weissman
- Laboratory of Ion Channels, The Mina and Everard Goodman Faculty of Life Sciences, Institute of Nanotechnology and Advanced Materials, Bar-Ilan UniversityRamat Gan, Israel
| | - Yoav Paas
- Laboratory of Ion Channels, The Mina and Everard Goodman Faculty of Life Sciences, Institute of Nanotechnology and Advanced Materials, Bar-Ilan UniversityRamat Gan, Israel
| |
Collapse
|
27
|
Contestabile A, Magara S, Cancedda L. The GABAergic Hypothesis for Cognitive Disabilities in Down Syndrome. Front Cell Neurosci 2017; 11:54. [PMID: 28326014 PMCID: PMC5339239 DOI: 10.3389/fncel.2017.00054] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Accepted: 02/14/2017] [Indexed: 12/04/2022] Open
Abstract
Down syndrome (DS) is a genetic disorder caused by the presence of a third copy of chromosome 21. DS affects multiple organs, but it invariably results in altered brain development and diverse degrees of intellectual disability. A large body of evidence has shown that synaptic deficits and memory impairment are largely determined by altered GABAergic signaling in trisomic mouse models of DS. These alterations arise during brain development while extending into adulthood, and include genesis of GABAergic neurons, variation of the inhibitory drive and modifications in the control of neural-network excitability. Accordingly, different pharmacological interventions targeting GABAergic signaling have proven promising preclinical approaches to rescue cognitive impairment in DS mouse models. In this review, we will discuss recent data regarding the complex scenario of GABAergic dysfunctions in the trisomic brain of DS mice and patients, and we will evaluate the state of current clinical research targeting GABAergic signaling in individuals with DS.
Collapse
Affiliation(s)
- Andrea Contestabile
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia (IIT) Genova, Italy
| | - Salvatore Magara
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia (IIT) Genova, Italy
| | - Laura Cancedda
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia (IIT)Genova, Italy; Dulbecco Telethon InstituteGenova, Italy
| |
Collapse
|
28
|
Degani-Katzav N, Klein M, Har-Even M, Gortler R, Tobi R, Paas Y. Trapping of ivermectin by a pentameric ligand-gated ion channel upon open-to-closed isomerization. Sci Rep 2017; 7:42481. [PMID: 28218274 PMCID: PMC5317004 DOI: 10.1038/srep42481] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 01/11/2017] [Indexed: 11/09/2022] Open
Abstract
Ivermectin (IVM) is a broad-spectrum anthelmintic drug used to treat human parasitic diseases like river blindness and lymphatic filariasis. By activating invertebrate pentameric glutamate-gated chloride channels (GluCl receptors; GluClRs), IVM induces sustained chloride influx and long-lasting membrane hyperpolarization that inhibit neural excitation in nematodes. Although IVM activates the C. elegans heteromeric GluClα/β receptor, it cannot activate a homomeric receptor composed of the C. elegans GluClβ subunits. To understand this incapability, we generated a homopentameric α7-GluClβ chimeric receptor that consists of an extracellular ligand-binding domain of an α7 nicotinic acetylcholine receptor known to be potentiated by IVM, and a chloride-selective channel domain assembled from GluClβ subunits. Application of IVM prior to acetylcholine inhibited the responses of the chimeric α7-GluClβR. Adding IVM to activated α7-GluClβRs, considerably accelerated the decline of ACh-elicited currents and stabilized the receptors in a non-conducting state. Determination of IVM association and dissociation rate constants and recovery experiments suggest that, following initial IVM binding to open α7-GluClβRs, the drug induces a conformational change and locks the ion channel in a closed state for a long duration. We further found that IVM also inhibits the activation by glutamate of a homomeric receptor assembled from the C. elegans full-length GluClβ subunits.
Collapse
Affiliation(s)
- Nurit Degani-Katzav
- Laboratory of Ion Channels, The Mina and Everard Goodman Faculty of Life Sciences and The Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 52900, Israel
| | - Moshe Klein
- Laboratory of Ion Channels, The Mina and Everard Goodman Faculty of Life Sciences and The Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 52900, Israel
| | - Moran Har-Even
- Laboratory of Ion Channels, The Mina and Everard Goodman Faculty of Life Sciences and The Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 52900, Israel
| | - Revital Gortler
- Laboratory of Ion Channels, The Mina and Everard Goodman Faculty of Life Sciences and The Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 52900, Israel
| | - Ruthi Tobi
- Laboratory of Ion Channels, The Mina and Everard Goodman Faculty of Life Sciences and The Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 52900, Israel
| | - Yoav Paas
- Laboratory of Ion Channels, The Mina and Everard Goodman Faculty of Life Sciences and The Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 52900, Israel
| |
Collapse
|
29
|
Carver CM, Reddy DS. Neurosteroid Structure-Activity Relationships for Functional Activation of Extrasynaptic δGABA(A) Receptors. J Pharmacol Exp Ther 2016; 357:188-204. [PMID: 26857959 DOI: 10.1124/jpet.115.229302] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2015] [Accepted: 02/05/2016] [Indexed: 01/18/2023] Open
Abstract
Synaptic GABAA receptors are primary mediators of rapid inhibition in the brain and play a key role in the pathophysiology of epilepsy and other neurologic disorders. The δ-subunit GABAA receptors are expressed extrasynaptically in the dentate gyrus and contribute to tonic inhibition, promoting network shunting as well as reducing seizure susceptibility. However, the neurosteroid structure-function relationship at δGABA(A) receptors within the native hippocampus neurons remains unclear. Here we report a structure-activity relationship for neurosteroid modulation of extrasynaptic GABAA receptor-mediated tonic inhibition in the murine dentate gyrus granule cells. We recorded neurosteroid allosteric potentiation of GABA as well as direct activation of tonic currents using a wide array of natural and synthetic neurosteroids. Our results shows that, for all neurosteroids, the C3α-OH group remains obligatory for extrasynaptic receptor functional activity, as C3β-OH epimers were inactive in activating tonic currents. Allopregnanolone and related pregnane analogs exhibited the highest potency and maximal efficacy in promoting tonic currents. Alterations at the C17 or C20 region of the neurosteroid molecule drastically altered the transduction kinetics of tonic current activation. The androstane analogs had the weakest modulatory response among the analogs tested. Neurosteroid potentiation of tonic currents was completely (approximately 95%) diminished in granule cells from δ-knockout mice, suggesting that δ-subunit receptors are essential for neurosteroid activity. The neurosteroid sensitivity of δGABA(A) receptors was confirmed at the systems level using a 6-Hz seizure test. A consensus neurosteroid pharmacophore model at extrasynaptic δGABA(A) receptors is proposed based on a structure-activity relationship for activation of tonic current and seizure protection.
Collapse
Affiliation(s)
- Chase Matthew Carver
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University Health Science Center, Bryan, Texas
| | - Doodipala Samba Reddy
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University Health Science Center, Bryan, Texas
| |
Collapse
|
30
|
Ondo W. Essential Tremor: What We Can Learn from Current Pharmacotherapy. Tremor Other Hyperkinet Mov (N Y) 2016; 6:356. [PMID: 26989572 PMCID: PMC4790207 DOI: 10.7916/d8k35tc3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Accepted: 12/17/2015] [Indexed: 04/07/2023] Open
Abstract
BACKGROUND The pathophysiology of essential tremor, especially at the cellular level, is poorly understood. Although no drug has been specifically designed to treat essential tremor, several medications improve tremor, and others worsen it. Studying the mechanism of actions of these medications can help our understanding of tremor pathophysiology and contribute to future rational drug design. METHODS We reviewed literature, concentrating on mechanisms of action, of various medications that mitigate tremor. RESULTS Many medications have multiple mechanisms of actions, making simple correlations difficult. Medications that increase the duration of opening of gamma-aminobutyric acid (GABA)-A receptors are most consistently associated with tremor improvement. Interestingly, drugs that increase GABA availability have not been associated with improved tremor. Other mechanisms possibly associated with tremor improvement include antagonism of alpha-2 delta subunits associated with calcium channels, inhibition of carbonic anhydrase, and inhibition of the synaptic vesicle protein 2A. Drugs that block voltage-gaited sodium channels do not affect tremor. The ideal beta-adrenergic blocker requires B2 affinity (non-cardiac selective), has no sympathomimetic properties, does not require membrane stabilization properties, and may benefit from good central nervous system penetration. DISCUSSION To date, serendipitous observations have provided most of our understanding of tremor cellular physiology. Based on similarities to currently effective drugs or rational approximations and inferences, several currently available agents should be considered for tremor trials.
Collapse
Affiliation(s)
- William Ondo
- Methodist Neurological Institute, Houston, TX, USA
- *To whom correspondence should be addressed. E-mail:
| |
Collapse
|
31
|
Herman JP, Tasker JG. Paraventricular Hypothalamic Mechanisms of Chronic Stress Adaptation. Front Endocrinol (Lausanne) 2016; 7:137. [PMID: 27843437 PMCID: PMC5086584 DOI: 10.3389/fendo.2016.00137] [Citation(s) in RCA: 128] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 10/03/2016] [Indexed: 01/02/2023] Open
Abstract
The hypothalamic paraventricular nucleus (PVN) is the primary driver of hypothalamo-pituitary-adrenocortical (HPA) responses. At least part of the role of the PVN is managing the demands of chronic stress exposure. With repeated exposure to stress, hypophysiotrophic corticotropin-releasing hormone (CRH) neurons of the PVN display a remarkable cellular, synaptic, and connectional plasticity that serves to maximize the ability of the HPA axis to maintain response vigor and flexibility. At the cellular level, chronic stress enhances the production of CRH and its co-secretagogue arginine vasopressin and rearranges neurotransmitter receptor expression so as to maximize cellular excitability. There is also evidence to suggest that efficacy of local glucocorticoid feedback is reduced following chronic stress. At the level of the synapse, chronic stress enhances cellular excitability and reduces inhibitory tone. Finally, chronic stress causes a structural enhancement of excitatory innervation, increasing the density of glutamate and noradrenergic/adrenergic terminals on CRH neuronal cell somata and dendrites. Together, these neuroplastic changes favor the ability of the HPA axis to retain responsiveness even under conditions of considerable adversity. Thus, chronic stress appears able to drive PVN neurons via a number of convergent mechanisms, processes that may play a major role in HPA axis dysfunction seen in variety of stress-linked disease states.
Collapse
Affiliation(s)
- James P. Herman
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, Cincinnati, OH, USA
- *Correspondence: James P. Herman,
| | - Jeffrey G. Tasker
- Department of Cell and Molecular Biology, Tulane Brain Institute, Tulane University, New Orleans, LA, USA
| |
Collapse
|
32
|
Bristow GC, Bostrom JA, Haroutunian V, Sodhi MS. Sex differences in GABAergic gene expression occur in the anterior cingulate cortex in schizophrenia. Schizophr Res 2015; 167:57-63. [PMID: 25660468 PMCID: PMC4524801 DOI: 10.1016/j.schres.2015.01.025] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Revised: 01/15/2015] [Accepted: 01/17/2015] [Indexed: 01/30/2023]
Abstract
GABAergic dysfunction has been strongly implicated in the pathophysiology of schizophrenia. In this study, we analyzed the expression levels of several GABAergic genes in the anterior cingulate cortex (ACC) of postmortem subjects with schizophrenia (n=21) and a comparison group of individuals without a history of psychiatric illness (n=18). Our analyses revealed a significant sex by diagnosis effect, along with significant differences in GABAergic gene expression based on medication status. Analyses revealed that in male groups, the expression of GABAergic genes was generally lower in schizophrenia cases compared to the controls, with significantly lower expression levels of GABA-Aα5, GABA-Aβ1, and GABA-Aε. In females, the expression of GABAergic genes was higher in the schizophrenia cases, with significantly higher expression of the GABA-Aβ1 and GAD67 genes. Analysis of the effect of medication in the schizophrenia subjects revealed significantly higher expression of GABA-Aα1-3, GABA-Aβ2, GABA-Aγ2, and GAD67 in the medicated group compared to the unmedicated group. These data show that sex differences in the expression of GABAergic genes occur in the ACC in schizophrenia. Therefore, our data support previous findings of GABAergic dysfunction in schizophrenia and emphasize the importance of considering sex in analyses of the pathophysiology of schizophrenia. Sex differences in the GABAergic regulation of ACC function may contribute to the differences observed in the symptoms of male and female patients with schizophrenia. In addition, our findings indicate that antipsychotic medications may alter GABAergic signaling in the ACC, supporting the potential of GABAergic targets for the development of novel antipsychotic medication.
Collapse
Affiliation(s)
- Greg C. Bristow
- Department of Pharmacy Practice and Center for Pharmaceutical Biotechnology, College of Pharmacy, University of Illinois at Chicago, Chicago IL 60607, USA.,Corresponding author: Dr. Greg Bristow, Department of Pharmacy Practice, University of Illinois at Chicago, 900 S. Ashland Ave., MC870, Chicago IL 60607-4067, USA. Tel: +1-312-996-1413, Fax: +1-312-413-9303,
| | - John A. Bostrom
- Department of Pharmacy Practice and Center for Pharmaceutical Biotechnology, College of Pharmacy, University of Illinois at Chicago, Chicago IL 60607, USA
| | - Vahram Haroutunian
- Department of Psychiatry, Mount Sinai School of Medicine, New York, NY, USA
| | - Monsheel S. Sodhi
- Department of Pharmacy Practice and Center for Pharmaceutical Biotechnology, College of Pharmacy, University of Illinois at Chicago, Chicago IL 60607, USA.,Department of Psychiatry, University of Illinois at Chicago, Chicago, IL 60612, USA
| |
Collapse
|
33
|
Comenencia-Ortiz E, Moss SJ, Davies PA. Phosphorylation of GABAA receptors influences receptor trafficking and neurosteroid actions. Psychopharmacology (Berl) 2014; 231:3453-65. [PMID: 24847959 PMCID: PMC4135009 DOI: 10.1007/s00213-014-3617-z] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Accepted: 05/02/2014] [Indexed: 01/06/2023]
Abstract
RATIONALE Gamma-aminobutyric acid type A receptors (GABAARs) are the principal mediators of inhibitory transmission in the mammalian central nervous system. GABAARs can be localized at post-synaptic inhibitory specializations or at extrasynaptic sites. While synaptic GABAARs are activated transiently following the release of GABA from presynaptic vesicles, extrasynaptic GABAARs are typically activated continuously by ambient GABA concentrations and thus mediate tonic inhibition. The tonic inhibitory currents mediated by extrasynaptic GABAARs control neuronal excitability and the strength of synaptic transmission. However, the mechanisms by which neurons control the functional properties of extrasynaptic GABAARs had not yet been explored. OBJECTIVES We review GABAARs, how they are assembled and trafficked, and the role phosphorylation has on receptor insertion and membrane stabilization. Finally, we review the modulation of GABAARs by neurosteroids and how GABAAR phosphorylation can influence the actions of neurosteroids. CONCLUSIONS Trafficking and stability of functional channels to the membrane surface are critical for inhibitory efficacy. Phosphorylation of residues within GABAAR subunits plays an essential role in the assembly, trafficking, and cell surface stability of GABAARs. Neurosteroids are produced in the brain and are highly efficacious allosteric modulators of GABAAR-mediated current. This allosteric modulation by neurosteroids is influenced by the phosphorylated state of the GABAAR which is subunit dependent, adding temporal and regional variability to the neurosteroid response. Possible links between neurosteroid actions, phosphorylation, and GABAAR trafficking remain to be explored, but potential novel therapeutic targets may exist for numerous neurological and psychological disorders which are linked to fluctuations in neurosteroid levels and GABAA subunit expression.
Collapse
|
34
|
Mapelli L, Solinas S, D'Angelo E. Integration and regulation of glomerular inhibition in the cerebellar granular layer circuit. Front Cell Neurosci 2014; 8:55. [PMID: 24616663 PMCID: PMC3933946 DOI: 10.3389/fncel.2014.00055] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Accepted: 02/06/2014] [Indexed: 11/26/2022] Open
Abstract
Inhibitory synapses can be organized in different ways and be regulated by a multitude of mechanisms. One of the best known examples is provided by the inhibitory synapses formed by Golgi cells onto granule cells in the cerebellar glomeruli. These synapses are GABAergic and inhibit granule cells through two main mechanisms, phasic and tonic. The former is based on vesicular neurotransmitter release, the latter on the establishment of tonic γ-aminobutyric acid (GABA) levels determined by spillover and regulation of GABA uptake. The mechanisms of post-synaptic integration have been clarified to a considerable extent and have been shown to differentially involve α1 and α6 subunit-containing GABA-A receptors. Here, after reviewing the basic mechanisms of GABAergic transmission in the cerebellar glomeruli, we examine how inhibition controls signal transfer at the mossy fiber-granule cell relay. First of all, we consider how vesicular release impacts on signal timing and how tonic GABA levels control neurotransmission gain. Then, we analyze the integration of these inhibitory mechanisms within the granular layer network. Interestingly, it turns out that glomerular inhibition is just one element in a large integrated signaling system controlled at various levels by metabotropic receptors. GABA-B receptor activation by ambient GABA regulates glutamate release from mossy fibers through a pre-synaptic cross-talk mechanisms, GABA release through pre-synaptic auto-receptors, and granule cell input resistance through post-synaptic receptor activation and inhibition of a K inward-rectifier current. Metabotropic glutamate receptors (mGluRs) control GABA release from Golgi cell terminals and Golgi cell input resistance and autorhythmic firing. This complex set of mechanisms implements both homeostatic and winner-take-all processes, providing the basis for fine-tuning inhibitory neurotransmission and for optimizing signal transfer through the cerebellar cortex.
Collapse
Affiliation(s)
- Lisa Mapelli
- Department of Brain and Behavioral Sciences, University of PaviaPavia, Italy
- Brain Connectivity Center, C. Mondino National Neurological InstitutePavia, Italy
| | - Sergio Solinas
- Department of Brain and Behavioral Sciences, University of PaviaPavia, Italy
- Brain Connectivity Center, C. Mondino National Neurological InstitutePavia, Italy
| | - Egidio D'Angelo
- Department of Brain and Behavioral Sciences, University of PaviaPavia, Italy
- Brain Connectivity Center, C. Mondino National Neurological InstitutePavia, Italy
| |
Collapse
|
35
|
Carver CM, Reddy DS. Neurosteroid interactions with synaptic and extrasynaptic GABA(A) receptors: regulation of subunit plasticity, phasic and tonic inhibition, and neuronal network excitability. Psychopharmacology (Berl) 2013; 230:151-88. [PMID: 24071826 PMCID: PMC3832254 DOI: 10.1007/s00213-013-3276-5] [Citation(s) in RCA: 171] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Accepted: 08/29/2013] [Indexed: 12/25/2022]
Abstract
RATIONALE Neurosteroids are steroids synthesized within the brain with rapid effects on neuronal excitability. Allopregnanolone, allotetrahydrodeoxycorticosterone, and androstanediol are three widely explored prototype endogenous neurosteroids. They have very different targets and functions compared to conventional steroid hormones. Neuronal γ-aminobutyric acid (GABA) type A (GABA(A)) receptors are one of the prime molecular targets of neurosteroids. OBJECTIVE This review provides a critical appraisal of recent advances in the pharmacology of endogenous neurosteroids that interact with GABA(A) receptors in the brain. Neurosteroids possess distinct, characteristic effects on the membrane potential and current conductance of the neuron, mainly via potentiation of GABA(A) receptors at low concentrations and direct activation of receptor chloride channel at higher concentrations. The GABA(A) receptor mediates two types of inhibition, now characterized as synaptic (phasic) and extrasynaptic (tonic) inhibition. Synaptic release of GABA results in the activation of low-affinity γ2-containing synaptic receptors, while high-affinity δ-containing extrasynaptic receptors are persistently activated by the ambient GABA present in the extracellular fluid. Neurosteroids are potent positive allosteric modulators of synaptic and extrasynaptic GABA(A) receptors and therefore enhance both phasic and tonic inhibition. Tonic inhibition is specifically more sensitive to neurosteroids. The resulting tonic conductance generates a form of shunting inhibition that controls neuronal network excitability, seizure susceptibility, and behavior. CONCLUSION The growing understanding of the mechanisms of neurosteroid regulation of the structure and function of the synaptic and extrasynaptic GABA(A) receptors provides many opportunities to create improved therapies for sleep, anxiety, stress, epilepsy, and other neuropsychiatric conditions.
Collapse
Affiliation(s)
- Chase Matthew Carver
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University Health Science Center, 2008 Medical Research and Education Building, 8447 State Highway 47, Bryan, TX, 77807-3260, USA
| | | |
Collapse
|
36
|
Jang HJ, Cho KH, Kim MJ, Yoon SH, Rhie DJ. Layer- and cell-type-specific tonic GABAergic inhibition of pyramidal neurons in the rat visual cortex. Pflugers Arch 2013; 465:1797-810. [DOI: 10.1007/s00424-013-1313-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Revised: 06/11/2013] [Accepted: 06/12/2013] [Indexed: 10/26/2022]
|
37
|
Auferkorte ON, Baden T, Kaushalya SK, Zabouri N, Rudolph U, Haverkamp S, Euler T. GABA(A) receptors containing the α2 subunit are critical for direction-selective inhibition in the retina. PLoS One 2012; 7:e35109. [PMID: 22506070 PMCID: PMC3323634 DOI: 10.1371/journal.pone.0035109] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Accepted: 03/13/2012] [Indexed: 01/08/2023] Open
Abstract
Far from being a simple sensor, the retina actively participates in processing visual signals. One of the best understood aspects of this processing is the detection of motion direction. Direction-selective (DS) retinal circuits include several subtypes of ganglion cells (GCs) and inhibitory interneurons, such as starburst amacrine cells (SACs). Recent studies demonstrated a surprising complexity in the arrangement of synapses in the DS circuit, i.e. between SACs and DS ganglion cells. Thus, to fully understand retinal DS mechanisms, detailed knowledge of all synaptic elements involved, particularly the nature and localization of neurotransmitter receptors, is needed. Since inhibition from SACs onto DSGCs is crucial for generating retinal direction selectivity, we investigate here the nature of the GABA receptors mediating this interaction. We found that in the inner plexiform layer (IPL) of mouse and rabbit retina, GABA(A) receptor subunit α2 (GABA(A)R α2) aggregated in synaptic clusters along two bands overlapping the dendritic plexuses of both ON and OFF SACs. On distal dendrites of individually labeled SACs in rabbit, GABA(A)R α2 was aligned with the majority of varicosities, the cell's output structures, and found postsynaptically on DSGC dendrites, both in the ON and OFF portion of the IPL. In GABA(A)R α2 knock-out (KO) mice, light responses of retinal GCs recorded with two-photon calcium imaging revealed a significant impairment of DS responses compared to their wild-type littermates. We observed a dramatic drop in the proportion of cells exhibiting DS phenotype in both the ON and ON-OFF populations, which strongly supports our anatomical findings that α2-containing GABA(A)Rs are critical for mediating retinal DS inhibition. Our study reveals for the first time, to the best of our knowledge, the precise functional localization of a specific receptor subunit in the retinal DS circuit.
Collapse
|
38
|
Alexeev M, Grosenbaugh DK, Mott DD, Fisher JL. The natural products magnolol and honokiol are positive allosteric modulators of both synaptic and extra-synaptic GABA(A) receptors. Neuropharmacology 2012; 62:2507-14. [PMID: 22445602 DOI: 10.1016/j.neuropharm.2012.03.002] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Accepted: 03/01/2012] [Indexed: 12/16/2022]
Abstract
The National Center for Complementary and Alternative Medicine (NCCAM) estimates that nearly 40% of adults in the United States use alternative medicines, often in the form of an herbal supplement. Extracts from the tree bark of magnolia species have been used for centuries in traditional Chinese and Japanese medicines to treat a variety of neurological diseases, including anxiety, depression, and seizures. The active ingredients in the extracts have been identified as the bi-phenolic isomers magnolol and honokiol. These compounds were shown to enhance the activity of GABA(A) receptors, consistent with their biological effects. The GABA(A) receptors exhibit substantial subunit heterogeneity, which influences both their functional and pharmacological properties. We examined the activity of magnolol and honokiol at different populations of both neuronal and recombinant GABA(A) receptors to characterize their mechanism of action and to determine whether sensitivity to modulation was dependent upon the receptor's subunit composition. We found that magnolol and honokiol enhanced both phasic and tonic GABAergic neurotransmission in hippocampal dentate granule neurons. In addition, all recombinant receptors examined were sensitive to modulation, regardless of the identity of the α, β, or γ subunit subtype, although the compounds showed particularly high efficacy at δ-containing receptors. This direct positive modulation of both synaptic and extra-synaptic populations of GABA(A) receptors suggests that supplements containing magnolol and/or honokiol would be effective anxiolytics, sedatives, and anti-convulsants. However, significant side-effects and risk of drug interactions would also be expected.
Collapse
Affiliation(s)
- Mikhail Alexeev
- Honors College, University of South Carolina, Columbia, SC 29208, USA
| | | | | | | |
Collapse
|
39
|
Oberlander JG, Penatti CAA, Porter DM, Henderson LP. The Buzz about anabolic androgenic steroids: electrophysiological effects in excitable tissues. Neuroendocrinology 2012; 96:141-51. [PMID: 22576754 PMCID: PMC3488447 DOI: 10.1159/000339123] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Accepted: 04/23/2012] [Indexed: 01/04/2023]
Abstract
Anabolic androgenic steroids (AAS) comprise a large and growing class of synthetic androgens used clinically to promote tissue-building in individuals suffering from genetic disorders, injuries, and diseases. Despite these beneficial therapeutic applications, the predominant use of AAS is illicit: these steroids are self-administered to promote athletic performance and body image. Hand in hand with the desired anabolic actions of the AAS are untoward effects on the brain and behavior. While the signaling routes by which the AAS impose both beneficial and harmful actions may be quite diverse, key endpoints are likely to include ligand-gated and voltage-dependent ion channels that govern the activity of electrically excitable tissues. Here, we review the known effects of AAS on molecular targets that play critical roles in controlling electrical activity, with a specific focus on the effects of AAS on neurotransmission mediated by GABA(A) receptors in the central nervous system.
Collapse
Affiliation(s)
- Joseph G. Oberlander
- Department of Physiology and Neurobiology, Dartmouth Medical School, Hanover, NH 03755 USA
| | - Carlos A. A. Penatti
- Departamento de Ciências Médicas, Universidade Nove de Julho - UNINOVE, São Paulo, SP 01504-000 Brasil
| | - Donna M. Porter
- Department of Physiology and Neurobiology, Dartmouth Medical School, Hanover, NH 03755 USA
| | - Leslie P. Henderson
- Department of Physiology and Neurobiology, Dartmouth Medical School, Hanover, NH 03755 USA
- To Whom Correspondence Should be Addressed:
| |
Collapse
|
40
|
Ellenbogen JM, Pace-Schott EF. Drug-induced sleep: theoretical and practical considerations. Pflugers Arch 2011; 463:177-86. [PMID: 21953011 DOI: 10.1007/s00424-011-1033-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Revised: 09/09/2011] [Accepted: 09/14/2011] [Indexed: 12/16/2022]
Abstract
Faithful replication of normal sleep through medications--can it be achieved? Departure from normal sleep with the use of drugs--when is it desired? Answers to these questions depend on accurate understanding of sleep and on concrete criteria upon which to define it. Since these elements are evolving sciences, as yet incompletely known, one might take a nihilistic approach that we simply cannot judge whether we have successfully replicated sleep, since we do not fully grasp what sleep is or what it does. To address these potential obstacles, our article is written in two sections. The first addresses theoretical considerations for how medications might be seen in the larger framework of sleep. The purpose of this section is to inform readers about key issues in evaluating whether a drug has sufficient data to persuasively argue it is re-creating sleep. (We hope that researchers interested in conducting studies, or critical readers of the drug-study literature, might find this section particularly useful.) The second section of this article approaches exemplary, current concepts of pharmacologic manipulation of sleep, organized by disorders as articulated by the International Classification of Sleep Disorders (2005). This second section will combine practical knowledge of clinical sleep medicine, with emphasis on contemporary knowledge about molecular mechanisms that are felt to underlie some of these phenomena. We recognize that our collective knowledge about sleep will advance in the coming years. We hope that this article serves to facilitate that advance.
Collapse
|
41
|
Jones SM, Palmer MJ. Pharmacological analysis of the activation and receptor properties of the tonic GABA(C)R current in retinal bipolar cell terminals. PLoS One 2011; 6:e24892. [PMID: 21949779 PMCID: PMC3174224 DOI: 10.1371/journal.pone.0024892] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Accepted: 08/22/2011] [Indexed: 11/29/2022] Open
Abstract
GABAergic inhibition in the central nervous system (CNS) can occur via rapid, transient postsynaptic currents and via a tonic increase in membrane conductance, mediated by synaptic and extrasynaptic GABAA receptors (GABAARs) respectively. Retinal bipolar cells (BCs) exhibit a tonic current mediated by GABACRs in their axon terminal, in addition to synaptic GABAAR and GABACR currents, which strongly regulate BC output. The tonic GABACR current in BC terminals (BCTs) is not dependent on vesicular GABA release, but properties such as the alternative source of GABA and the identity of the GABACRs remain unknown. Following a recent report that tonic GABA release from cerebellar glial cells is mediated by Bestrophin 1 anion channels, we have investigated their role in non-vesicular GABA release in the retina. Using patch-clamp recordings from BCTs in goldfish retinal slices, we find that the tonic GABACR current is not reduced by the anion channel inhibitors NPPB or flufenamic acid but is reduced by DIDS, which decreases the tonic current without directly affecting GABACRs. All three drugs also exhibit non-specific effects including inhibition of GABA transporters. GABACR ρ subunits can form homomeric and heteromeric receptors that differ in their properties, but BC GABACRs are thought to be ρ1-ρ2 heteromers. To investigate whether GABACRs mediating tonic and synaptic currents may differ in their subunit composition, as is the case for GABAARs, we have examined the effects of two antagonists that show partial ρ subunit selectivity: picrotoxin and cyclothiazide. Tonic and synaptic GABACR currents were differentially affected by both drugs, suggesting that a population of homomeric ρ1 receptors contributes to the tonic current. These results extend our understanding of the multiple forms of GABAergic inhibition that exist in the CNS and contribute to visual signal processing in the retina.
Collapse
Affiliation(s)
- Stefanie M. Jones
- Neuroscience Group, Institute for Science and Technology in Medicine, Keele University, Keele, United Kingdom
| | - Mary J. Palmer
- Neuroscience Group, Institute for Science and Technology in Medicine, Keele University, Keele, United Kingdom
- * E-mail:
| |
Collapse
|
42
|
Abstract
GABAA receptors mediate the majority of the fast inhibition in the mature brain and play an important role in the pathogenesis of many neurological and psychiatric disorders. The αβδ GABAA receptor localizes extra- or perisynaptically and mediates GABAergic tonic inhibition. Compared with synaptically localized αβγ receptors, αβδ receptors are more sensitive to GABA, display relatively slower desensitization and exhibit lower efficacy to GABA agonism. Interestingly, αβδ receptors can be positively modulated by a variety of structurally different compounds, even at saturating GABA concentrations. This review focuses on allosteric modulation of recombinant αβδ receptor currents and αβδ receptor-mediated tonic currents by anesthetics and ethanol. The possible mechanisms for the positive modulation of αβδ receptors by these compounds will also be discussed.
Collapse
|
43
|
Abstract
After five editions, the congress on "Steroids and Nervous System" held in Torino, Italy, represents an important international event for researchers involved in this field aimed to recapitulate mechanisms, physiological and pharmacological effects of neuroactive steroids. The present review introduces manuscripts collected in this supplement issue which are based on new interesting findings such as the influence of sex steroids on cannabinoid-regulated biology, the role of steroids in pain, the importance of co-regulators in steroidal mechanisms and the understanding of new non classical mechanism, the emerging role of vitamin D as a neuroactive steroid and the pathogenetic mechanisms mediated by glucocorticoid receptors. Finally, we have integrated these aspects with an update on some of the several and important observations recently published on this hot topic.
Collapse
|