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Schmuhl-Giesen S, Rollenhagen A, Walkenfort B, Yakoubi R, Sätzler K, Miller D, von Lehe M, Hasenberg M, Lübke JHR. Sublamina-Specific Dynamics and Ultrastructural Heterogeneity of Layer 6 Excitatory Synaptic Boutons in the Adult Human Temporal Lobe Neocortex. Cereb Cortex 2021; 32:1840-1865. [PMID: 34530440 PMCID: PMC9070345 DOI: 10.1093/cercor/bhab315] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Synapses “govern” the computational properties of any given network in the brain. However, their detailed quantitative morphology is still rather unknown, particularly in humans. Quantitative 3D-models of synaptic boutons (SBs) in layer (L)6a and L6b of the temporal lobe neocortex (TLN) were generated from biopsy samples after epilepsy surgery using fine-scale transmission electron microscopy, 3D-volume reconstructions and electron microscopic tomography. Beside the overall geometry of SBs, the size of active zones (AZs) and that of the three pools of synaptic vesicles (SVs) were quantified. SBs in L6 of the TLN were middle-sized (~5 μm2), the majority contained only a single but comparatively large AZ (~0.20 μm2). SBs had a total pool of ~1100 SVs with comparatively large readily releasable (RRP, ~10 SVs L6a), (RRP, ~15 SVs L6b), recycling (RP, ~150 SVs), and resting (~900 SVs) pools. All pools showed a remarkably large variability suggesting a strong modulation of short-term synaptic plasticity. In conclusion, L6 SBs are highly reliable in synaptic transmission within the L6 network in the TLN and may act as “amplifiers,” “integrators” but also as “discriminators” for columnar specific, long-range extracortical and cortico-thalamic signals from the sensory periphery.
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Affiliation(s)
| | - Astrid Rollenhagen
- Institute of Neuroscience and Medicine INM-10, Research Centre Jülich GmbH, 52425, Jülich, Germany
| | - Bernd Walkenfort
- Imaging Center Essen (IMCES), Electron Microscopy Unit (EMU), Medical Faculty of the University of Duisburg-Essen, 45147, Essen, Germany
| | - Rachida Yakoubi
- Institute of Neuroscience and Medicine INM-10, Research Centre Jülich GmbH, 52425, Jülich, Germany
| | - Kurt Sätzler
- School of Biomedical Sciences, University of Ulster, Londonderry, BT52 1SA, UK
| | - Dorothea Miller
- University Hospital/Knappschaftskrankenhaus Bochum, 44892, Bochum, Germany
| | - Marec von Lehe
- Department of Neurosurgery, Brandenburg Medical School, Ruppiner Clinics, 16816, Neuruppin, Germany
| | - Mike Hasenberg
- Imaging Center Essen (IMCES), Electron Microscopy Unit (EMU), Medical Faculty of the University of Duisburg-Essen, 45147, Essen, Germany
| | - Joachim H R Lübke
- Address correspondence to Joachim Lübke, Institute of Neuroscience and Medicine INM-10, Research Centre Jülich GmbH, 52425 Jülich, Germany.
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2
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Cunha-Reis D, Caulino-Rocha A, Correia-de-Sá P. VIPergic neuroprotection in epileptogenesis: challenges and opportunities. Pharmacol Res 2021; 164:105356. [DOI: 10.1016/j.phrs.2020.105356] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 11/28/2020] [Accepted: 11/29/2020] [Indexed: 12/19/2022]
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3
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Yakoubi R, Rollenhagen A, von Lehe M, Shao Y, Sätzler K, Lübke JHR. Quantitative Three-Dimensional Reconstructions of Excitatory Synaptic Boutons in Layer 5 of the Adult Human Temporal Lobe Neocortex: A Fine-Scale Electron Microscopic Analysis. Cereb Cortex 2020; 29:2797-2814. [PMID: 29931200 DOI: 10.1093/cercor/bhy146] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Revised: 05/22/2018] [Accepted: 05/29/2018] [Indexed: 11/14/2022] Open
Abstract
Studies of synapses are available for different brain regions of several animal species including non-human primates, but comparatively little is known about their quantitative morphology in humans. Here, synaptic boutons in Layer 5 (L5) of the human temporal lobe (TL) neocortex were investigated in biopsy tissue, using fine-scale electron microscopy, and quantitative three-dimensional reconstructions. The size and organization of the presynaptic active zones (PreAZs), postsynaptic densities (PSDs), and that of the 3 distinct pools of synaptic vesicles (SVs) were particularly analyzed. L5 synaptic boutons were medium-sized (~6 μm2) with a single but relatively large PreAZ (~0.3 μm2). They contained a total of ~1500 SVs/bouton, ~20 constituting the putative readily releasable pool (RRP), ~180 the recycling pool (RP), and the remainder, the resting pool. The PreAZs, PSDs, and vesicle pools are ~3-fold larger than those of CNS synapses in other species. Astrocytic processes reached the synaptic cleft and may regulate the glutamate concentration. Profound differences exist between synapses in human TL neocortex and those described in various species, particularly in the size and geometry of PreAZs and PSDs, the large RRP/RP, and the astrocytic ensheathment suggesting high synaptic efficacy, strength, and modulation of synaptic transmission at human synapses.
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Affiliation(s)
- Rachida Yakoubi
- Institute of Neuroscience and Medicine INM-10, Research Centre Jülich GmbH, Leo-Brandt Str., Jülich, Germany
| | - Astrid Rollenhagen
- Institute of Neuroscience and Medicine INM-10, Research Centre Jülich GmbH, Leo-Brandt Str., Jülich, Germany
| | - Marec von Lehe
- University Hospital/Knappschaftskrankenhaus Bochum, In der Schornau 23-25, Bochum, Germany.,Department of Neurosurgery, Ruppiner Kliniken, Medizinische Hochschule Brandenburg, Fehrbelliner Str. 38, Neuruppin, Germany
| | - Yachao Shao
- Simulation Lab Neuroscience, Research Centre Jülich GmbH, Leo-Brandt Str., Jülich, Germany.,College of Computer, National University of Defense Technology, Changsha, China
| | - Kurt Sätzler
- School of Biomedical Sciences, University of Ulster, Cromore Rd., BT52 1SA, Londonderry, UK
| | - Joachim H R Lübke
- Institute of Neuroscience and Medicine INM-10, Research Centre Jülich GmbH, Leo-Brandt Str., Jülich, Germany.,Department of Psychiatry, Psychotherapy and Psychosomatics, Medical Faculty/RWTH University Hospital Aachen, Pauwelsstr. 30, Aachen, Germany.,JARA Translational Brain Medicine, Germany
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4
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Martinez-Arroyo O, Ortega A, Perez-Hernandez J, Chaves FJ, Redon J, Cortes R. The Rab-Rabphilin system in injured human podocytes stressed by glucose overload and angiotensin II. Am J Physiol Renal Physiol 2020; 319:F178-F191. [PMID: 32567349 PMCID: PMC7473899 DOI: 10.1152/ajprenal.00077.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Kidney injury in hypertension and diabetes entails, among in other structures, damage in a key cell of the glomerular filtration barrier, the podocyte. Podocytes are polarized and highly differentiated cells in which vesicular transport, partly driven by Rab GTPases, is a relevant process. The aim of the present study was to analyze Rab GTPases of the Rab-Rabphilin system in human immortalized podocytes and the impact of high glucose and angiotensin II. Furthermore, alterations of the system in urine cell pellets from patients with hypertension and diabetes were studied. Apoptosis was analyzed in podocytes, and mRNA level quantification, Western blot analysis, and immunofluorescence were developed to quantify podocyte-specific molecules and Rab-Rabphilin components (Rab3A, Rab27A, and Rabphilin3A). Quantitative RT-PCR was performed on urinary cell pellet from patients. The results showed that differentiated cells had reduced protein levels of the Rab-rabphillin system compared with undifferentiated cells. After glucose overload and angiotensin II treatment, apoptosis was increased and podocyte-specific proteins were reduced. Rab3A and Rab27A protein levels were increased under glucose overload, and Rabphilin3A decreased. Furthermore, this system exhibited higher levels under stress conditions in a manner of angiotensin II dose and time treatment. Immunofluorescence imaging indicated different expression patterns of podocyte markers and Rab27A under treatments. Finally, Rab3A and Rab27A were increased in patient urine pellets and showed a direct relationship with albuminuria. Collectively, these results suggest that the Rab-Rabphilin system could be involved in the alterations observed in injured podocytes and that a mechanism may be activated to reduce damage through the vesicular transport enhancement directed by this system.
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Affiliation(s)
- Olga Martinez-Arroyo
- Cardiometabolic and Renal Risk Research Group, INCLIVA Biomedical Research Institute, Valencia, Spain
| | - Ana Ortega
- Cardiometabolic and Renal Risk Research Group, INCLIVA Biomedical Research Institute, Valencia, Spain
| | - Javier Perez-Hernandez
- Cardiometabolic and Renal Risk Research Group, INCLIVA Biomedical Research Institute, Valencia, Spain
| | - Felipe J Chaves
- Genomics and Diabetes Unit, INCLIVA Biomedical Research Institute, Valencia, Spain.,CIBER of Diabetes and Associated Metabolic Diseases, Institute of Health Carlos III, Minister of Health, Barcelona, Spain
| | - Josep Redon
- Cardiometabolic and Renal Risk Research Group, INCLIVA Biomedical Research Institute, Valencia, Spain.,Internal Medicine Unit, Hospital Clínico Universitario, Valencia, Spain.,CIBER of Physiopathology of Obesity and Nutrition, Institute of Health Carlos III, Minister of Health, Madrid, Spain
| | - Raquel Cortes
- Cardiometabolic and Renal Risk Research Group, INCLIVA Biomedical Research Institute, Valencia, Spain
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Cunha-Reis D, Caulino-Rocha A. VIP Modulation of Hippocampal Synaptic Plasticity: A Role for VIP Receptors as Therapeutic Targets in Cognitive Decline and Mesial Temporal Lobe Epilepsy. Front Cell Neurosci 2020; 14:153. [PMID: 32595454 PMCID: PMC7303298 DOI: 10.3389/fncel.2020.00153] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Accepted: 05/11/2020] [Indexed: 12/19/2022] Open
Abstract
Vasoactive intestinal peptide (VIP) is an important modulatory peptide throughout the CNS acting as a neurotransmitter, neurotrophic or neuroprotective factor. In the hippocampus, a brain area implicated in learning and memory processes, VIP has a crucial role in the control of GABAergic transmission and pyramidal cell activity in response to specific network activity by either VIP-containing basket cells or interneuron-selective (IS) interneurons and this appears to have a differential impact in hippocampal-dependent cognition. At the cellular level, VIP regulates synaptic transmission by either promoting disinhibition, through activation of VPAC1 receptors, or enhancing pyramidal cell excitability, through activation of VPAC2 receptors. These actions also control several important synaptic plasticity phenomena such as long-term potentiation (LTP) and long-term depression (LTD). This paper reviews the current knowledge on the activation and multiple functions of VIP expressing cells in the hippocampus and their role in controlling synaptic transmission, synaptic plasticity and learning and memory processes, discussing also the role of VPAC1 and VPAC2 VIP receptors in the regulation of these different processes. Furthermore, we address the current knowledge regarding changes in VIP mediated neurotransmission in epileptogenesis and mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS), and discuss the therapeutic opportunities of using selective VIP receptor ligands to prevent epileptogenesis and cognitive decline in MTLE-HS.
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Affiliation(s)
- Diana Cunha-Reis
- BioISI - Biosystems and Integrative Sciences Institute, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal.,Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal
| | - Ana Caulino-Rocha
- BioISI - Biosystems and Integrative Sciences Institute, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal.,Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal
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6
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Yakoubi R, Rollenhagen A, von Lehe M, Miller D, Walkenfort B, Hasenberg M, Sätzler K, Lübke JH. Ultrastructural heterogeneity of layer 4 excitatory synaptic boutons in the adult human temporal lobe neocortex. eLife 2019; 8:48373. [PMID: 31746736 PMCID: PMC6919978 DOI: 10.7554/elife.48373] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Accepted: 11/19/2019] [Indexed: 01/09/2023] Open
Abstract
Synapses are fundamental building blocks controlling and modulating the ‘behavior’ of brain networks. How their structural composition, most notably their quantitative morphology underlie their computational properties remains rather unclear, particularly in humans. Here, excitatory synaptic boutons (SBs) in layer 4 (L4) of the temporal lobe neocortex (TLN) were quantitatively investigated. Biopsies from epilepsy surgery were used for fine-scale and tomographic electron microscopy (EM) to generate 3D-reconstructions of SBs. Particularly, the size of active zones (AZs) and that of the three functionally defined pools of synaptic vesicles (SVs) were quantified. SBs were comparatively small (~2.50 μm2), with a single AZ (~0.13 µm2); preferentially established on spines. SBs had a total pool of ~1800 SVs with strikingly large readily releasable (~20), recycling (~80) and resting pools (~850). Thus, human L4 SBs may act as ‘amplifiers’ of signals from the sensory periphery, integrate, synchronize and modulate intra- and extracortical synaptic activity.
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Affiliation(s)
- Rachida Yakoubi
- Institute of Neuroscience and Medicine INM-10, Research Centre Jülich GmbH, Jülich, Germany
| | - Astrid Rollenhagen
- Institute of Neuroscience and Medicine INM-10, Research Centre Jülich GmbH, Jülich, Germany
| | - Marec von Lehe
- Department of Neurosurgery, Knappschaftskrankenhaus Bochum, Bochum, Germany.,Department of Neurosurgery, Brandenburg Medical School, Ruppiner Clinics, Neuruppin, Germany
| | - Dorothea Miller
- Department of Neurosurgery, Knappschaftskrankenhaus Bochum, Bochum, Germany
| | - Bernd Walkenfort
- Medical Research Centre, IMCES Electron Microscopy Unit (EMU), University Hospital Essen, Essen, Germany
| | - Mike Hasenberg
- Medical Research Centre, IMCES Electron Microscopy Unit (EMU), University Hospital Essen, Essen, Germany
| | - Kurt Sätzler
- School of Biomedical Sciences, University of Ulster, Londonderry, United Kingdom
| | - Joachim Hr Lübke
- Institute of Neuroscience and Medicine INM-10, Research Centre Jülich GmbH, Jülich, Germany.,Department of Psychiatry, Psychotherapy and Psychosomatics, Faculty of Medicine, RWTH University Hospital Aachen, Aachen, Germany.,JARA Translational Brain Medicine, Jülich/Aachen, Germany
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7
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Prume M, Rollenhagen A, Lübke JHR. Structural and Synaptic Organization of the Adult Reeler Mouse Somatosensory Neocortex: A Comparative Fine-Scale Electron Microscopic Study of Reeler With Wild Type Mice. Front Neuroanat 2018; 12:80. [PMID: 30344480 PMCID: PMC6182073 DOI: 10.3389/fnana.2018.00080] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Accepted: 09/13/2018] [Indexed: 11/17/2022] Open
Abstract
The reeler mouse has been widely used to study various aspects of cortico- and synaptogenesis, but also as a model for several neurological and neurodegenerative disorders. In contrast to development, comparably little is known about the neuronal composition and synaptic organization of the adult reeler mouse neocortex, in particular at the fine-scale electron microscopic level, which was investigated here and compared with wild type (WT) mice. In this study, the “barrel field” of the adult reeler and WT mouse somatosensory neocortex is used as a model system. In reeler the characteristic six-layered structure is no longer existent, but replaced by a conglomerate of neurons organized in homologous clusters with maintained morphological identity and heterologous clusters between neurons and/or oligodendrocytes. These clusters are loosely scattered throughout the neocortical mass between the pial surface and the white matter. In contrast to WT, layer 1 (L1), if existent, seems to be diluted into the volume of the neocortical mass with no clear boundary. L1 also contains clusters of migrated or persistent neurons, oligodendro- and astrocytes. As in WT, myelinated and unmyelinated axons were found throughout the neocortical mass, but in reeler they were organized in massive fiber bundles with a high fiber packing density. A prominent and massive thalamocortical projection traverses through the neocortical mass, always accompanied by numerous “active” oligodendrocytes whereas in WT no such projections were found and “silent” oligodendrocytes were restricted to the white matter. In the adult reeler mouse neocortex, synaptic boutons terminate on somata, dendritic shafts, spines of different types and axon initial segments with no signs of structural distortion and/or degeneration, indicating a “normal” postsynaptic innervation pattern of neurons. In addition, synaptic complexes between boutons and their postsynaptic targets are tightly ensheathed by fine astrocytic processes, as in WT. In conclusion, the neuronal clusters may represent a possible alternative organization principle in adult reeler mice “replacing” layer formation. If so, these homologous clusters may represent individual “functional units” where neurons are highly interconnected and may function as the equivalent of neurons integrated in a cortical layer. The structural composition and postsynaptic innervation pattern of neurons by synaptic boutons provide the structural basis for the establishment of a functional although altered cortical network in the adult reeler mouse.
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Affiliation(s)
- Miriam Prume
- Institute of Neuroscience and Medicine INM-10, Research Centre Jülich GmbH, Jülich, Germany
| | - Astrid Rollenhagen
- Institute of Neuroscience and Medicine INM-10, Research Centre Jülich GmbH, Jülich, Germany
| | - Joachim H R Lübke
- Institute of Neuroscience and Medicine INM-10, Research Centre Jülich GmbH, Jülich, Germany.,Department of Psychiatry, Psychotherapy and Psychosomatics, Medical Faculty, RWTH University Hospital Aachen, Aachen, Germany.,JARA Translational Brain Medicine, Jülich, Germany
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8
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Neural Cotransmission in Spinal Circuits Governing Locomotion. Trends Neurosci 2018; 41:540-550. [DOI: 10.1016/j.tins.2018.04.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Revised: 04/06/2018] [Accepted: 04/17/2018] [Indexed: 01/08/2023]
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9
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Cunha-Reis D, Ribeiro JA, de Almeida RFM, Sebastião AM. VPAC 1 and VPAC 2 receptor activation on GABA release from hippocampal nerve terminals involve several different signalling pathways. Br J Pharmacol 2017; 174:4725-4737. [PMID: 28945273 DOI: 10.1111/bph.14051] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Revised: 09/19/2017] [Accepted: 09/19/2017] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND AND PURPOSE Vasoactive intestinal peptide (VIP) is an important modulator of hippocampal synaptic transmission that influences both GABAergic synaptic transmission and glutamatergic cell excitability through activation of VPAC1 and VPAC2 receptors. Presynaptic enhancement of GABA release contributes to VIP modulation of hippocampal synaptic transmission. EXPERIMENTAL APPROACH We investigated which VIP receptors and coupled transduction pathways were involved in VIP enhancement of K+ -evoked [3 H]-GABA release from isolated nerve terminals of rat hippocampus. KEY RESULTS VIP enhancement of [3 H]-GABA release was potentiated in the presence of the VPAC1 receptor antagonist PG 97-269 but converted into an inhibition in the presence of the VPAC2 receptor antagonist PG 99-465, suggesting that activation of VPAC1 receptors inhibits and activation of VPAC2 receptors enhances, GABA release. A VPAC1 receptor agonist inhibited exocytotic voltage-gated calcium channel (VGCC)-dependent [3 H]-GABA release through activation of protein Gi/o , an effect also dependent on PKC activity. A VPAC2 receptor agonist enhanced both exocytotic VGCC-dependent release through protein Gs -dependent, PKA-dependent and PKC-dependent mechanisms and GABA transporter 1-mediated [3 H]-GABA release through a Gs protein-dependent and PKC-dependent mechanism. CONCLUSIONS AND IMPLICATIONS Our results show that VPAC1 and VPAC2 VIP receptors have opposing actions on GABA release from hippocampal nerve terminals through activation of different transduction pathways. As VPAC1 and VPAC2 receptors are located in different layers of Ammon's horn, our results suggest that these VIP receptors underlie different modulation of synaptic transmission to pyramidal cell dendrites and cell bodies, with important consequences for their possible therapeutic application in the treatment of epilepsy.
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Affiliation(s)
- Diana Cunha-Reis
- Instituto de Farmacologia e Neurociências e, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal.,Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal.,Centro de Química e Bioquímica, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal
| | - Joaquim Alexandre Ribeiro
- Instituto de Farmacologia e Neurociências e, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal.,Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
| | - Rodrigo F M de Almeida
- Centro de Química e Bioquímica, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal
| | - Ana M Sebastião
- Instituto de Farmacologia e Neurociências e, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal.,Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
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10
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Gonzalez-Obeso E, Docio I, Olea E, Cogolludo A, Obeso A, Rocher A, Gomez-Niño A. Guinea Pig Oxygen-Sensing and Carotid Body Functional Properties. Front Physiol 2017; 8:285. [PMID: 28533756 PMCID: PMC5420588 DOI: 10.3389/fphys.2017.00285] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 04/19/2017] [Indexed: 01/06/2023] Open
Abstract
Mammals have developed different mechanisms to maintain oxygen supply to cells in response to hypoxia. One of those mechanisms, the carotid body (CB) chemoreceptors, is able to detect physiological hypoxia and generate homeostatic reflex responses, mainly ventilatory and cardiovascular. It has been reported that guinea pigs, originally from the Andes, have a reduced ventilatory response to hypoxia compared to other mammals, implying that CB are not completely functional, which has been related to genetically/epigenetically determined poor hypoxia-driven CB reflex. This study was performed to check the guinea pig CB response to hypoxia compared to the well-known rat hypoxic response. These experiments have explored ventilatory parameters breathing different gases mixtures, cardiovascular responses to acute hypoxia, in vitro CB response to hypoxia and other stimuli and isolated guinea pig chemoreceptor cells properties. Our findings show that guinea pigs are hypotensive and have lower arterial pO2 than rats, probably related to a low sympathetic tone and high hemoglobin affinity. Those characteristics could represent a higher tolerance to hypoxic environment than other rodents. We also find that although CB are hypo-functional not showing chronic hypoxia sensitization, a small percentage of isolated carotid body chemoreceptor cells contain tyrosine hydroxylase enzyme and voltage-dependent K+ currents and therefore can be depolarized. However hypoxia does not modify intracellular Ca2+ levels or catecholamine secretion. Guinea pigs are able to hyperventilate only in response to intense acute hypoxic stimulus, but hypercapnic response is similar to rats. Whether other brain areas are also activated by hypoxia in guinea pigs remains to be studied.
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Affiliation(s)
- Elvira Gonzalez-Obeso
- Servicio de Anatomía Patológica, Hospital Clínico Universitario de ValladolidValladolid, Spain
| | - Inmaculada Docio
- Departamento de Bioquímica y Biología Molecular y Fisiología, Universidad de Valladolid, IBGM, CSICValladolid, Spain.,CIBER de Enfermedades Respiratorias, ISCiiiSpain
| | - Elena Olea
- CIBER de Enfermedades Respiratorias, ISCiiiSpain.,Departamento de Enfermería, Universidad de Valladolid, IBGM, CSICValladolid, Spain
| | - Angel Cogolludo
- CIBER de Enfermedades Respiratorias, ISCiiiSpain.,Departamento de Farmacología, Instituto de Investigación Sanitaria Gregorio Marañón, Universidad Complutense de MadridMadrid, Spain
| | - Ana Obeso
- Departamento de Bioquímica y Biología Molecular y Fisiología, Universidad de Valladolid, IBGM, CSICValladolid, Spain.,CIBER de Enfermedades Respiratorias, ISCiiiSpain
| | - Asuncion Rocher
- Departamento de Bioquímica y Biología Molecular y Fisiología, Universidad de Valladolid, IBGM, CSICValladolid, Spain.,CIBER de Enfermedades Respiratorias, ISCiiiSpain
| | - Angela Gomez-Niño
- CIBER de Enfermedades Respiratorias, ISCiiiSpain.,Departamento de Biología Celular, Histología y Farmacología, Universidad de Valladolid, IBGM, CSICValladolid, Spain
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11
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Control of Amygdala Circuits by 5-HT Neurons via 5-HT and Glutamate Cotransmission. J Neurosci 2017; 37:1785-1796. [PMID: 28087766 PMCID: PMC5320609 DOI: 10.1523/jneurosci.2238-16.2016] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Revised: 11/07/2016] [Accepted: 11/19/2016] [Indexed: 11/21/2022] Open
Abstract
The serotonin (5-HT) system and the amygdala are key regulators of emotional behavior. Several lines of evidence suggest that 5-HT transmission in the amygdala is implicated in the susceptibility and drug treatment of mood disorders. Therefore, elucidating the physiological mechanisms through which midbrain 5-HT neurons modulate amygdala circuits could be pivotal in understanding emotional regulation in health and disease. To shed light on these mechanisms, we performed patch-clamp recordings from basal amygdala (BA) neurons in brain slices from mice with channelrhodopsin genetically targeted to 5-HT neurons. Optical stimulation of 5-HT terminals at low frequencies (≤1 Hz) evoked a short-latency excitation of BA interneurons (INs) that was depressed at higher frequencies. Pharmacological analysis revealed that this effect was mediated by glutamate and not 5-HT because it was abolished by ionotropic glutamate receptor antagonists. Optical stimulation of 5-HT terminals at higher frequencies (10–20 Hz) evoked both slow excitation and slow inhibition of INs. These effects were mediated by 5-HT because they were blocked by antagonists of 5-HT2A and 5-HT1A receptors, respectively. These fast glutamate- and slow 5-HT-mediated responses often coexisted in the same neuron. Interestingly, fast-spiking and non-fast-spiking INs displayed differential modulation by glutamate and 5-HT. Furthermore, optical stimulation of 5-HT terminals did not evoke glutamate release onto BA principal neurons, but inhibited these cells directly via activation of 5-HT1A receptors and indirectly via enhanced GABA release. Collectively, these findings suggest that 5-HT neurons exert a frequency-dependent, cell-type-specific control over BA circuitry via 5-HT and glutamate co-release to inhibit the BA output. SIGNIFICANCE STATEMENT The modulation of the amygdala by serotonin (5-HT) is important for emotional regulation and is implicated in the pathogenesis and treatment of affective disorders. Therefore, it is essential to determine the physiological mechanisms through which 5-HT neurons in the dorsal raphe nuclei modulate amygdala circuits. Here, we combined optogenetic, electrophysiological, and pharmacological approaches to study the effects of activation of 5-HT axons in the basal nucleus of the amygdala (BA). We found that 5-HT neurons co-release 5-HT and glutamate onto BA neurons in a cell-type-specific and frequency-dependent manner. Therefore, we suggest that theories on the contribution of 5-HT neurons to amygdala function should be revised to incorporate the concept of 5-HT/glutamate cotransmission.
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12
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What optogenetic stimulation is telling us (and failing to tell us) about fast neurotransmitters and neuromodulators in brain circuits for wake-sleep regulation. Curr Opin Neurobiol 2014; 29:165-71. [PMID: 25064179 DOI: 10.1016/j.conb.2014.07.016] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Revised: 07/07/2014] [Accepted: 07/07/2014] [Indexed: 12/19/2022]
Abstract
In the last eight years optogenetic tools have been widely used to identify functional synaptic connectivity between specific neuronal populations. Most of our knowledge comes from the photo-activation of channelrhodopsin-2 (ChR2) expressing inputs that release glutamate and GABA. More recent studies have been reporting releases of acetylcholine and biogenic amines but direct evidence for photo-evoked released of neuropeptides is still limited particularly in brain slice studies. The high fidelity in the responses with photo-evoked amino-acid transmission is ideal for ChR2-assisted circuit mapping and this approach has been successfully used in different fields of neuroscience. Conversely, neuropeptides employ a slow mode of communication and might require higher frequency and prolonged stimulations to be released. These factors may have contributed to the apparent lack of success for optogenetic release of neuropeptides. In addition, once released, neuropeptides often act on multiple sites and at various distances from the site of release resulting in a greater complexity of postsynaptic responses. Here, we focus on what optogenetics is telling us-and failing to tell us-about fast neurotransmitters and neuropeptides.
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Migheli R, Del Giudice MG, Spissu Y, Sanna G, Xiong Y, Dawson TM, Dawson VL, Galioto M, Rocchitta G, Biosa A, Serra PA, Carri MT, Crosio C, Iaccarino C. LRRK2 affects vesicle trafficking, neurotransmitter extracellular level and membrane receptor localization. PLoS One 2013; 8:e77198. [PMID: 24167564 PMCID: PMC3805556 DOI: 10.1371/journal.pone.0077198] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Accepted: 09/07/2013] [Indexed: 01/20/2023] Open
Abstract
The leucine-rich repeat kinase 2 (LRRK2) gene was found to play a role in the pathogenesis of both familial and sporadic Parkinson’s disease (PD). LRRK2 encodes a large multi-domain protein that is expressed in different tissues. To date, the physiological and pathological functions of LRRK2 are not clearly defined. In this study we have explored the role of LRRK2 in controlling vesicle trafficking in different cellular or animal models and using various readouts. In neuronal cells, the presence of LRRK2G2019S pathological mutant determines increased extracellular dopamine levels either under basal conditions or upon nicotine stimulation. Moreover, mutant LRRK2 affects the levels of dopamine receptor D1 on the membrane surface in neuronal cells or animal models. Ultrastructural analysis of PC12-derived cells expressing mutant LRRK2G2019S shows an altered intracellular vesicle distribution. Taken together, our results point to the key role of LRRK2 to control vesicle trafficking in neuronal cells.
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Affiliation(s)
- Rossana Migheli
- Department of Clinical and Experimental Medicine, University of Sassari, Sassari, Italy
| | | | - Ylenia Spissu
- Department of Clinical and Experimental Medicine, University of Sassari, Sassari, Italy
| | - Giovanna Sanna
- Department of Biomedical Sciences, University of Sassari, Sassari, Italy
| | - Yulan Xiong
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Ted M. Dawson
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Valina L. Dawson
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Manuela Galioto
- Department of Biomedical Sciences, University of Sassari, Sassari, Italy
| | - Gaia Rocchitta
- Department of Clinical and Experimental Medicine, University of Sassari, Sassari, Italy
| | - Alice Biosa
- Department of Clinical and Experimental Medicine, University of Sassari, Sassari, Italy
| | - Pier Andrea Serra
- Department of Clinical and Experimental Medicine, University of Sassari, Sassari, Italy
| | - Maria Teresa Carri
- Fondazione Santa Lucia, IRCCS, Rome, Italy
- Department of Biology, University of Rome “Tor Vergata”, Rome, Italy
| | - Claudia Crosio
- Department of Biomedical Sciences, University of Sassari, Sassari, Italy
- Fondazione Santa Lucia, IRCCS, Rome, Italy
| | - Ciro Iaccarino
- Department of Biomedical Sciences, University of Sassari, Sassari, Italy
- Fondazione Santa Lucia, IRCCS, Rome, Italy
- * E-mail:
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Mortensen OV. MKP3 eliminates depolarization-dependent neurotransmitter release through downregulation of L-type calcium channel Cav1.2 expression. Cell Calcium 2013; 53:224-30. [PMID: 23337371 DOI: 10.1016/j.ceca.2012.12.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Revised: 12/06/2012] [Accepted: 12/24/2012] [Indexed: 01/17/2023]
Abstract
Release of neurotransmitters is a fundamental and regulated process that is essential for normal brain functioning. Regulation of this process is potentially important for any neuronal process, and disruption of the release process may contribute to the pathophysiology associated with psychiatric diseases. In this work it is shown that expression of the negative regulator of mitogen-activated protein kinase (MAPK) signaling the MAPK phosphatase MKP3/DUSP6 eliminates depolarization-dependent release of dopamine in rat PC12 cells. Pharmacologic interventions with latrotroxin (LTX) or A23187, which make the cells permeable to calcium, reestablish the dopamine release. Calcium imaging also reveals that calcium influx is impaired in MKP3-expressing cells. Because acute pharmacologic inhibition of MAPKs has no effect on dopamine release in naïve PC12 cells, the MKP3-mediated elimination of neurotransmitter release must be caused by a long-term process, such as changes in gene expression. In support of this the expression of the L-type calcium channel cav1.2 alpha subunit (Cacna1c) is decreased in MKP3-expressing PC12 cells. With the reintroduction of cav1.2 expression, neurotransmitter release is restored in the MKP3-expressing PC12 cells. Thus, MKP3 expression reduces neurotransmitter release by decreasing the expression of cav1.2. Because MKP3 is increased when neuronal activity is elevated, this process could play a role in regulating neurotransmitter homeostasis.
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Affiliation(s)
- Ole V Mortensen
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA 19102, USA.
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Wang G, Qi Y, Gao L, Li G, Lv X, Jin Y. Effects of subacute exposure to 1,2-dichloroethane on mouse behavior and the related mechanisms. Hum Exp Toxicol 2012; 32:983-91. [DOI: 10.1177/0960327112470270] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The aim of this study was to explore the effects of subacute exposure to 1,2-dichloroethane (1,2-DCE) on mouse behavior and the related mechanisms focusing on alteration of oxidative stress and amino acid neurotransmitters in the brain. Mouse behavior was examined by open field test. Levels of nitric oxide (NO), malondialdehyde (MDA) and nonprotein sulfhydryl (NPSH) and activity of inducible nitric oxide synthase (iNOS) and superoxide dismutase (SOD) were determined by colorimetric method. Contents of glutamate (Glu), aspartate (Asp) and gamma-aminobutyric acid (GABA) were evaluated by high-performance liquid chromatography. Reduced locomotor and exploratory activities and increased anxiety were found in 0.45 and 0.9 g/m3 1,2-DCE-treated mice. In contrast, increased excitability was found in 0.225 g/m3 1,2-DCE-treated mice. Compensatory antioxidant status and increased NOS activity and NO level in the brain were found in 1,2-DCE-treated mice. Moreover, Glu contents in 1,2-DCE-treated mice and GABA contents in 0.9 g/m3 1,2-DCE-treated mice increased, whereas GABA contents in 0.225 g/m3 1,2-DCE-treated mice decreased significantly compared with control. Taken together, our results suggested that mouse behavior could be disturbed by subacute exposure to 1,2-DCE, and the changes of amino acid neurotransmitter in the brain might be related to the behavioral effects.
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Affiliation(s)
- G. Wang
- Department of Occupational and Environmental Health, School of Public Health, China Medical University, Shenyang, Liaoning, People’s Republic of China
| | - Y. Qi
- Department of Occupational and Environmental Health, School of Public Health, China Medical University, Shenyang, Liaoning, People’s Republic of China
| | - L. Gao
- Department of Occupational and Environmental Health, School of Public Health, China Medical University, Shenyang, Liaoning, People’s Republic of China
| | - G. Li
- Department of Occupational and Environmental Health, School of Public Health, China Medical University, Shenyang, Liaoning, People’s Republic of China
| | - X. Lv
- Department of Occupational and Environmental Health, School of Public Health, China Medical University, Shenyang, Liaoning, People’s Republic of China
| | - Y.P. Jin
- Department of Occupational and Environmental Health, School of Public Health, China Medical University, Shenyang, Liaoning, People’s Republic of China
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Nusbaum MP, Blitz DM. Neuropeptide modulation of microcircuits. Curr Opin Neurobiol 2012; 22:592-601. [PMID: 22305485 DOI: 10.1016/j.conb.2012.01.003] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2012] [Accepted: 01/10/2012] [Indexed: 11/29/2022]
Abstract
Neuropeptides provide functional flexibility to microcircuits, their inputs and effectors by modulating presynaptic and postsynaptic properties and intrinsic currents. Recent studies have relied less on applied neuropeptide and more on their neural release. In rhythmically active microcircuits (central pattern generators, CPGs), recent studies show that neuropeptide modulation can enable particular activity patterns by organizing specific circuit motifs. Neuropeptides can also modify microcircuit output indirectly, by modulating circuit inputs. Recently elucidated consequences of neuropeptide modulation include changes in motor patterns and behavior, stabilization of rhythmic motor patterns and changes in CPG sensitivity to sensory input. One aspect of neuropeptide modulation that remains enigmatic is the presence of multiple peptide family members in the same nervous system and even the same neurons.
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Affiliation(s)
- Michael P Nusbaum
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6074, United States.
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Abstract
Cysteine-string protein (CSP), a member of the DnaJ/Hsp40 family of cochaperones, is critical for maintaining neurotransmitter release and preventing neurodegeneration. CSP likely forms a chaperone complex on synaptic vesicles together with the 70-kDa heat shock cognate (Hsc70) and the small glutamine-rich tetratricopeptide repeat (TPR)-containing protein (SGT) that may control or protect the assembly and activity of SNARE proteins and various other protein substrates. Here, the author summarizes studies that elucidated CSP's neuroprotective role.
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Affiliation(s)
- Konrad E Zinsmaier
- Department of Neuroscience and Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721-0077, USA.
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Merighi A, Salio C, Ferrini F, Lossi L. Neuromodulatory function of neuropeptides in the normal CNS. J Chem Neuroanat 2011; 42:276-87. [PMID: 21385606 DOI: 10.1016/j.jchemneu.2011.02.001] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Revised: 02/08/2011] [Accepted: 02/09/2011] [Indexed: 01/15/2023]
Abstract
Neuropeptides are small protein molecules produced and released by discrete cell populations of the central and peripheral nervous systems through the regulated secretory pathway and acting on neural substrates. Inside the nerve cells, neuropeptides are selectively stored within large granular vesicles (LGVs), and commonly coexist in neurons with low-molecular-weight neurotransmitters (acetylcholine, amino acids, and catecholamines). Storage in LGVs is responsible for a relatively slow response to secretion that requires enhanced or repeated stimulation. Coexistence (i.e. the concurrent presence of a neuropeptide with other messenger molecules in individual neurons), and co-storage (i.e. the localization of two or more neuropeptides within individual LGVs in neurons) give rise to a complicated series of pre- and post-synaptic functional interactions with low-molecular-weight neurotransmitters. The typically slow response and action of neuropeptides as compared to fast-neurotransmitters such as excitatory/inhibitory amino acids and catecholamines is also due to the type of receptors that trigger neuropeptide actions onto target cells. Almost all neuropeptides act on G-protein coupled receptors that, upon ligand binding, activate an intracellular cascade of molecular enzymatic events, eventually leading to cellular responses. The latter occur in a time span (seconds or more) considerably longer (milliseconds) than that of low-molecular-weight fast-neurotransmitters, directly operating through ion channel receptors. As reviewed here, combined immunocytochemical visualization of neuropeptides and their receptors at the ultrastructural level and electrophysiological studies, have been fundamental to better unravel the role of neuropeptides in neuron-to-neuron communication.
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Affiliation(s)
- Adalberto Merighi
- University of Turin, Department of Veterinary Morphophysiology, Via Leonardo da Vinci 44, 10095 Grugliasco, Torino, Italy.
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ABE H, OKA Y. Mechanisms of Neuromodulation by a Nonhypophysiotropic GnRH System Controlling Motivation of Reproductive Behavior in the Teleost Brain. J Reprod Dev 2011; 57:665-74. [DOI: 10.1262/jrd.11-055e] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Hideki ABE
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan
| | - Yoshitaka OKA
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan
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DeLong ND, Beenhakker MP, Nusbaum MP. Presynaptic inhibition selectively weakens peptidergic cotransmission in a small motor system. J Neurophysiol 2009; 102:3492-504. [PMID: 19828722 DOI: 10.1152/jn.00833.2009] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The presence and influence of neurons containing multiple neurotransmitters is well established, including the ability of coreleased transmitters to influence the same or different postsynaptic targets. Little is known, however, regarding whether presynaptic regulation of multitransmitter neurons influences all transmission from these neurons. Using the identified neurons and motor networks in the crab stomatogastric ganglion, we document the ability of presynaptic inhibition to selectively inhibit peptidergic cotransmission. Specifically, we determine that the gastropyloric receptor (GPR) proprioceptor neuron uses presynaptic inhibition to selectively regulate peptidergic cotransmission from the axon terminals of MCN1, a projection neuron that drives the biphasic (retraction, protraction) gastric mill (chewing) rhythm. MCN1 drives this rhythm via fast GABAergic excitation of the retraction neuron Int1 and slow peptidergic excitation of the lateral gastric (LG) protraction neuron. We first demonstrate that GPR inhibition of the MCN1 axon terminals is serotonergic and then establish that this serotonergic inhibition weakens MCN1 peptidergic excitation of LG without altering MCN1 GABAergic excitation of Int1. At the circuit level, we show that this selective regulation of MCN1 peptidergic cotransmission is necessary for the normal GPR regulation of the gastric mill rhythm. This is the first demonstration, at the level of individual identified neurons, that a presynaptic input can selectively regulate a subset of coreleased transmitters. This selective regulation changes the balance of cotransmitter actions by the target multitransmitter neuron, thereby enabling this neuron to have state-dependent actions on its target network. This finding reveals additional flexibility afforded by the ability of neurons to corelease multiple neurotransmitters.
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Affiliation(s)
- Nicholas D DeLong
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6074, USA
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Abstract
Drugs of abuse usurp the mechanisms underlying synaptic plasticity in areas of the brain, a process that may contribute to the development of addiction. We previously reported that GABAergic synapses onto dopaminergic neurons in the ventral tegmental area (VTA) exhibit long-term potentiation (LTP(GABA)) blocked by in vivo exposure to morphine. The presynaptically maintained LTP requires the retrogradely released nitric oxide (NO) to activate a presynaptic cGMP signaling cascade. Previous work reported that inhibitory GABA(A) receptor synapses in the VTA are also potentiated by cAMP. Here, we explored the interactions between cGMP-dependent (PKG) and cAMP-dependent (PKA) protein kinases in the regulation of these GABAergic synapses and LTP(GABA). Activation of PKG was required for NO-cGMP signaling and was also essential for the induction of synaptically elicited LTP(GABA), but not for its maintenance. Synapses containing GABA(A) receptors were potentiated by NO-cGMP signaling, whereas synapses containing GABA(B) receptors on the same cells were not potentiated. Moreover, although the cAMP-PKA system potentiated GABA(A) synapses, synaptically induced LTP(GABA) was independent of PKA activation. Surprisingly, however, raising cGMP levels saturated potentiation of these synapses, precluding further potentiation by cAMP and suggesting a convergent end point for both signaling pathways in the regulation of GABAergic release. We further found that persistent GABAergic synaptic modifications observed with in vivo morphine did not involve the presynaptic cAMP-PKA cascade. Taken together, our data suggest a synapse-specific role for NO-cGMP-PKG signaling pathway in opioid-induced plasticity of VTA GABA(A) synapses.
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Wojcik SM, Brose N. Regulation of Membrane Fusion in Synaptic Excitation-Secretion Coupling: Speed and Accuracy Matter. Neuron 2007; 55:11-24. [PMID: 17610814 DOI: 10.1016/j.neuron.2007.06.013] [Citation(s) in RCA: 142] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Unlike most other secretory processes, neurotransmitter release at chemical synapses is extremely fast, tightly regulated, spatially restricted, and dynamically adjustable at the same time. In this review, we focus on recent discoveries of molecular and cell biological processes that determine how fusion competence of vesicles is achieved and controlled in order to suit the specific requirements of synaptic transmitter release with respect to speed and spatial selectivity.
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Affiliation(s)
- Sonja M Wojcik
- Max-Planck-Institut für Experimentelle Medizin, Abteilung Molekulare Neurobiologie, Hermann-Rein-Strasse 3, D-37075 Göttingen, Deutschland.
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Tallent MK. Presynaptic inhibition of glutamate release by neuropeptides: use-dependent synaptic modification. Results Probl Cell Differ 2007; 44:177-200. [PMID: 17554500 DOI: 10.1007/400_2007_037] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Neuropeptides are signaling molecules that interact with G-protein coupled receptors located both pre- and postsynaptically. Presynaptically, these receptors are localized in axons and terminals away from presynaptic specializations. Neuropeptides are stored in dense core vesicles that are distinct from the clear synaptic vesicles containing classic neurotransmitters such as glutamate and GABA. Because they require a stronger Ca(2+) signal than synaptic vesicles, dense core vesicles do not release neuropeptides with single action potentials but rather require high-frequency trains. Thus, neuropeptides only modulate strongly stimulated synapses, providing negative or positive feedback. Many neuropeptides have been found to inhibit glutamate release from presynaptic terminals, and the major mechanism is likely direct interaction of betagamma G-protein subunits with presynaptic proteins such as SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor). The use of mouse genetic models and specific receptor antagonists are beginning to unravel the function of inhibitory neuropeptides. The opioid receptors kappa and mu, which are activated by endogenous opioid peptides such as dynorphin, enkephalin, and possibly the endomorphins, are important in modulating pain transmission. Dynorphin, nociceptin/orphanin FQ, and somatostatin and its related peptide cortistatin appear to play a role in modulation of learning and memory. Neuropeptide Y has important functions in ingestive behavior and also in entraining circadian rhythms. The existence of neuropeptides greatly expands the computational ability of the brain by providing additional levels of modulation.
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Affiliation(s)
- Melanie K Tallent
- Department of Pharmacology and Physiology, Philadelphia, PA 19102, USA.
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Spergel DJ. Calcium and small-conductance calcium-activated potassium channels in gonadotropin-releasing hormone neurons before, during, and after puberty. Endocrinology 2007; 148:2383-90. [PMID: 17289846 PMCID: PMC3315592 DOI: 10.1210/en.2006-1693] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The pubertal increase in GnRH secretion resulting in sexual maturation and reproductive competence is a complex process involving kisspeptin stimulation of GnRH neurons and requiring Ca(2+) and possibly other intracellular messengers. To determine whether the expression of Ca(2+) channels, or small-conductance Ca(2+)-activated K(+) (SK) channels, whose activity reflects cytoplasmic free Ca(2+) concentration, changes at puberty in GnRH neurons, Ca(2+) and SK currents in GnRH neurons were recorded in brain slices of juvenile [postnatal day (P) 10-21], pubertal (P28-P42), and adult (> or =P56) male GnRH-green fluorescent protein transgenic mice using perforated-patch and whole-cell techniques. Ca(2+) currents were inhibited by the Ca(2+) channel blocker Cd(2+) and showed marked heterogeneity but were on average similar in juvenile, pubertal, and adult GnRH neurons. SK currents, which were inhibited by the SK channel blocker apamin and enhanced by the SK and intermediate-conductance Ca(2+)-activated K(+) channel activator 1-ethyl-2-benzimidazolinone, were also on average similar in juvenile, pubertal, and adult GnRH neurons. These findings suggest that whereas Ca(2+) and SK channels may participate in the pubertal increase in GnRH secretion and there may be changes in Ca(2+) or SK channel subtypes, overall Ca(2+) and SK channel expression in GnRH neurons remains relatively constant across pubertal development. Hence, the expected increase in GnRH neuron cytoplasmic free Ca(2+) concentration required for increased GnRH secretion at puberty appears to be due to mechanisms other than altered Ca(2+) or SK channel expression, e.g. increased membrane depolarization and subsequent activation of preexisting Ca(2+) channels after increased excitatory synaptic input.
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Affiliation(s)
- Daniel J Spergel
- Section of Endocrinology, Department of Pediatrics, University of Chicago, Illinois 60637-1470, USA.
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Cagide E, Louzao MC, Ares IR, Vieytes MR, Yotsu-Yamashita M, Paquette LA, Yasumoto T, Botana LM. Effects of a Synthetic Analog of Polycavernoside A on Human Neuroblastoma Cells. Cell Physiol Biochem 2007; 19:185-94. [PMID: 17310112 DOI: 10.1159/000099206] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/24/2006] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Polycavernoside A is a glycosidic marine toxin first extracted from the red alga Polycavernosa tsudai in 1991 when 3 people died after the ingestion of this food. Polycavernoside A is an interesting molecule because of its complex macrolide structure and strong bioactivity. However, the target site of this toxin has not been characterized. METHODS We studied the effects of a synthethic analog of polycavernoside A on human neuroblastoma cells by measuring changes in membrane potential with bis-oxonol and variations in intracellular calcium levels with fura-2. Fluorescent phalloidin was utilized for assaying activity on actin cytoskeleton. RESULTS Data showed that this polycavernoside A analog induced a membrane depolarization and an increase in cytosolic calcium levels. CONCLUSION These results provide the first insight into the mode of action of polycavernoside A, suggesting that: i) this toxin triggers an initial extracellular calcium entry neither produced across L-type voltage-gated calcium channels nor activation of muscarinic receptors ii) there is a depolarization induced by the toxin and due to the extracellular calcium entry.
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Affiliation(s)
- Eva Cagide
- Departamento de Farmacologia. Facultad de Veterinaria. Universidad de Santiago de Compostela. Campus de Lugo. Lugo, Spain
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Rollenhagen A, Lübke JHR. The morphology of excitatory central synapses: from structure to function. Cell Tissue Res 2006; 326:221-37. [PMID: 16932936 DOI: 10.1007/s00441-006-0288-z] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2006] [Accepted: 06/14/2006] [Indexed: 11/28/2022]
Abstract
Synapses are the key elements for signal transduction and plasticity in the brain. For a better understanding of the functional signal cascades underlying synaptic transmission, a quantitative morphological analysis of the pre- and postsynaptic structures that represent morphological correlates for synaptic transmission is important. In particular, realistic values of the number, distribution, and geometry of synaptic contacts and the organization of the pool of synaptic vesicles provide important constraints for realistic models and numerical simulations of those parameters of synaptic transmission that, at present, are still not accessible to experiment. Although all synapses are composed of almost the same structural elements, the composition of these elements within a given synapse and the microcircuit in which they are embedded are the deciding factors determining its function. One possible way to analyze these structures is by computer-assisted three-dimensional reconstructions of synapses and their subsequent quantitative analysis based on ultrathin serial sections. The present review summarizes and discusses the morphology of five central excitatory synapses that are quantitatively well described: (1) a giant synapse, the so-called Calyx of Held, in the medial nucleus of the trapezoid body in the auditory brain stem, (2) the mossy fiber terminal establishing synapses with multiple cerebellar granule cell dendrites, (3) the mossy fiber bouton in the hippocampus predominantly terminating on proximal dendrites of CA3 pyramidal neurons, (4) the climbing fiber-Purkinje cell synapse in the cerebellum, and (5) cortical input synapses on the basal dendrites of layer 5 pyramidal cells. The detailed morphological description of these synaptic structures may help to define the morphological correlates of the functional parameters of synaptic transmission, such as the readily releasable pool of synaptic vesicles, of release, and of the variability of quantal size and might therefore explain the existing differences in the function between individual synapses embedded in different microcircuits.
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Affiliation(s)
- Astrid Rollenhagen
- Institute of Neuroscience and Biophysics, Department of Medicine, Research Center Jülich, D-52425, Jülich, Germany
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Kubista H, Boehm S. Molecular mechanisms underlying the modulation of exocytotic noradrenaline release via presynaptic receptors. Pharmacol Ther 2006; 112:213-42. [PMID: 16730801 DOI: 10.1016/j.pharmthera.2006.04.005] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2006] [Accepted: 04/10/2006] [Indexed: 10/24/2022]
Abstract
The release of noradrenaline from nerve terminals is modulated by a variety of presynaptic receptors. These receptors belong to one of the following three receptor superfamilies: transmitter-gated ion channels, G protein-coupled receptors (GPCR), and membrane receptors with intracellular enzymatic activities. For representatives of each of these three superfamilies, receptor activation has been reported to cause either an enhancement or a reduction of noradrenaline release. As these receptor classes display greatly diverging structures and functions, a multitude of different molecular mechanisms are involved in the regulation of noradrenaline release via presynaptic receptors. This review gives a short overview of the presynaptic receptors on noradrenergic nerve terminals and summarizes the events involved in vesicle exocytosis in order to finally delineate the most important signaling cascades that mediate the modulation via presynaptic receptors. In addition, the interactions between the various presynaptic receptors are described and the underlying molecular mechanisms are elucidated. Together, these presynaptic signaling mechanisms form a sophisticated network that precisely adapts the amount of noradrenaline being released to a given situation.
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Affiliation(s)
- Helmut Kubista
- Institute of Pharmacology, Centre of Biomolecular Medicine and Pharmacology, Medical University of Vienna, Waehringer Strasse 13a, A-1090 Vienna, Austria
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McMullan R, Hiley E, Morrison P, Nurrish SJ. Rho is a presynaptic activator of neurotransmitter release at pre-existing synapses in C. elegans. Genes Dev 2006; 20:65-76. [PMID: 16391233 PMCID: PMC1356101 DOI: 10.1101/gad.359706] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Rho GTPases have important roles in neuronal development, but their function in adult neurons is less well understood. We demonstrate that presynaptic changes in Rho activity at Caenorhabditis elegans neuromuscular junctions can radically change animal behavior via modulation of two separate pathways. In one, presynaptic Rho increases acetylcholine (ACh) release by stimulating the accumulation of diacylglycerol (DAG) and the DAG-binding protein UNC-13 at sites of neurotransmitter release; this pathway requires binding of Rho to the DAG kinase DGK-1. A second DGK-1-independent mechanism is revealed by the ability of a Rho inhibitor (C3 transferase) to decrease levels of release even in the absence of DGK-1; this pathway is independent of UNC-13 accumulation at release sites. We do not detect any Rho-induced changes in neuronal morphology or synapse number; thus, Rho facilitates synaptic transmission by a novel mechanism. Surprisingly, many commonly available human RhoA constructs contain an uncharacterized mutation that severely reduces binding of RhoA to DAG kinase. Thus, a role for RhoA in controlling DAG levels is likely to have been underestimated.
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Affiliation(s)
- Rachel McMullan
- MRC Cell Biology Unit, MRC Laboratory for Molecular Cell Biology and Department of Pharmacology, University College, London WC1E 6BT, United Kingdom
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