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Díaz F, Aguilar F, Wellmann M, Martorell A, González-Arancibia C, Chacana-Véliz L, Negrón-Oyarzo I, Chávez AE, Fuenzalida M, Nualart F, Sotomayor-Zárate R, Bonansco C. Enhanced Astrocyte Activity and Excitatory Synaptic Function in the Hippocampus of Pentylenetetrazole Kindling Model of Epilepsy. Int J Mol Sci 2023; 24:14506. [PMID: 37833953 PMCID: PMC10572460 DOI: 10.3390/ijms241914506] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 09/12/2023] [Accepted: 09/17/2023] [Indexed: 10/15/2023] Open
Abstract
Epilepsy is a chronic condition characterized by recurrent spontaneous seizures. The interaction between astrocytes and neurons has been suggested to play a role in the abnormal neuronal activity observed in epilepsy. However, the exact way astrocytes influence neuronal activity in the epileptogenic brain remains unclear. Here, using the PTZ-induced kindling mouse model, we evaluated the interaction between astrocyte and synaptic function by measuring astrocytic Ca2+ activity, neuronal excitability, and the excitatory/inhibitory balance in the hippocampus. Compared to control mice, hippocampal slices from PTZ-kindled mice displayed an increase in glial fibrillary acidic protein (GFAP) levels and an abnormal pattern of intracellular Ca2+-oscillations, characterized by an increased frequency of prolonged spontaneous transients. PTZ-kindled hippocampal slices also showed an increase in the E/I ratio towards excitation, likely resulting from an augmented release probability of excitatory inputs without affecting inhibitory synapses. Notably, the alterations in the release probability seen in PTZ-kindled slices can be recovered by reducing astrocyte hyperactivity with the reversible toxin fluorocitrate. This suggests that astroglial hyper-reactivity enhances excitatory synaptic transmission, thereby impacting the E/I balance in the hippocampus. Altogether, our findings support the notion that abnormal astrocyte-neuron interactions are pivotal mechanisms in epileptogenesis.
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Affiliation(s)
- Franco Díaz
- Centro de Neurobiología y Fisiopatología Integrativa (CENFI), Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2360102, Chile; (F.D.); (F.A.); (M.W.); (A.M.); (C.G.-A.); (L.C.-V.); (I.N.-O.); (M.F.)
- Escuela de Ciencias de la Salud, Universidad Viña del Mar, Viña del Mar 2580022, Chile
- Programa de Magíster en Ciencias Biológicas mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2360102, Chile
| | - Freddy Aguilar
- Centro de Neurobiología y Fisiopatología Integrativa (CENFI), Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2360102, Chile; (F.D.); (F.A.); (M.W.); (A.M.); (C.G.-A.); (L.C.-V.); (I.N.-O.); (M.F.)
- Programa de Magíster en Ciencias Biológicas mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2360102, Chile
| | - Mario Wellmann
- Centro de Neurobiología y Fisiopatología Integrativa (CENFI), Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2360102, Chile; (F.D.); (F.A.); (M.W.); (A.M.); (C.G.-A.); (L.C.-V.); (I.N.-O.); (M.F.)
- Programa de Magíster en Ciencias Biológicas mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2360102, Chile
| | - Andrés Martorell
- Centro de Neurobiología y Fisiopatología Integrativa (CENFI), Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2360102, Chile; (F.D.); (F.A.); (M.W.); (A.M.); (C.G.-A.); (L.C.-V.); (I.N.-O.); (M.F.)
- Programa de Magíster en Ciencias Biológicas mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2360102, Chile
- Escuela de Fonoaudiología, Facultad de Salud, Universidad Santo Tomás, Viña del Mar 2561780, Chile
| | - Camila González-Arancibia
- Centro de Neurobiología y Fisiopatología Integrativa (CENFI), Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2360102, Chile; (F.D.); (F.A.); (M.W.); (A.M.); (C.G.-A.); (L.C.-V.); (I.N.-O.); (M.F.)
| | - Lorena Chacana-Véliz
- Centro de Neurobiología y Fisiopatología Integrativa (CENFI), Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2360102, Chile; (F.D.); (F.A.); (M.W.); (A.M.); (C.G.-A.); (L.C.-V.); (I.N.-O.); (M.F.)
| | - Ignacio Negrón-Oyarzo
- Centro de Neurobiología y Fisiopatología Integrativa (CENFI), Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2360102, Chile; (F.D.); (F.A.); (M.W.); (A.M.); (C.G.-A.); (L.C.-V.); (I.N.-O.); (M.F.)
| | - Andrés E. Chávez
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2360102, Chile;
| | - Marco Fuenzalida
- Centro de Neurobiología y Fisiopatología Integrativa (CENFI), Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2360102, Chile; (F.D.); (F.A.); (M.W.); (A.M.); (C.G.-A.); (L.C.-V.); (I.N.-O.); (M.F.)
| | - Francisco Nualart
- Laboratory of Neurobiology and Stem Cells, NeuroCellT, Department of Cellular Biology, Faculty of Biological Sciences, University of Concepcion, Concepción 4070386, Chile;
- Center for Advanced Microscopy CMA BIOBIO, Faculty of Biological Sciences, University of Concepcion, Concepción 4070386, Chile
| | - Ramón Sotomayor-Zárate
- Centro de Neurobiología y Fisiopatología Integrativa (CENFI), Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2360102, Chile; (F.D.); (F.A.); (M.W.); (A.M.); (C.G.-A.); (L.C.-V.); (I.N.-O.); (M.F.)
| | - Christian Bonansco
- Centro de Neurobiología y Fisiopatología Integrativa (CENFI), Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2360102, Chile; (F.D.); (F.A.); (M.W.); (A.M.); (C.G.-A.); (L.C.-V.); (I.N.-O.); (M.F.)
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Ahumada-Marchant C, Ancatén-Gonzalez C, Haensgen H, Arancibia F, Brauer B, Droste R, Horvitz HR, Constantine-Paton M, Arriagada G, Chávez AE, Bustos FJ. Deletion of VPS50 protein in mice brain impairs synaptic function and behavior. bioRxiv 2023:2023.07.04.547745. [PMID: 37461727 PMCID: PMC10349947 DOI: 10.1101/2023.07.04.547745] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 07/28/2023]
Abstract
VPS50, is an accessory protein, involved in the synaptic and dense core vesicle acidification and its alterations produce behavioral changes in C.elegans. Here, we produce the mosaic knock out (mKO) of VPS50 using CRISPR/Cas9 system in both cortical cultured neurons and whole animals to evaluate the effect of VPS50 in regulating mammalian brain function and behavior. While mKO of VPS50 does not change the number of synaptic vesicles, it produces a mislocalization of the V-ATPase pump that likely impact in vesicle acidification and vesicle content to impair synaptic and neuronal activity in cultured neurons. In mice, mKO of VPS50 in the hippocampus, alter synaptic transmission and plasticity, and generated robust cognitive impairments associate to memory formation. We propose that VPS50 is an accessory protein that aids the correct recruitment of the V-ATPase pump to synaptic vesicles, thus having a crucial role controlling synaptic vesicle acidification and hence synaptic transmission.
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Affiliation(s)
- Constanza Ahumada-Marchant
- Instituto de Ciencias Biomedicas, Facultad de Medicina y Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago, Chile
| | - Carlos Ancatén-Gonzalez
- Programa de Doctorado en Ciencias, Mención Neurociencia, Universidad de Valparaíso, Valparaíso, Chile
- Instituto de Neurociencias, Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Henny Haensgen
- Instituto de Ciencias Biomedicas, Facultad de Medicina y Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago, Chile
| | - Felipe Arancibia
- Instituto de Ciencias Biomedicas, Facultad de Medicina y Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago, Chile
| | - Bastian Brauer
- Instituto de Ciencias Biomedicas, Facultad de Medicina y Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago, Chile
| | - Rita Droste
- Massachusetts Institute of Technology Cambridge, MA 02139, USA
| | | | | | - Gloria Arriagada
- Instituto de Ciencias Biomedicas, Facultad de Medicina y Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago, Chile
| | - Andrés E Chávez
- Instituto de Neurociencias, Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Fernando J Bustos
- Instituto de Ciencias Biomedicas, Facultad de Medicina y Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago, Chile
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3
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Ancatén-González C, Segura I, Alvarado-Sánchez R, Chávez AE, Latorre R. Ca 2+- and Voltage-Activated K + (BK) Channels in the Nervous System: One Gene, a Myriad of Physiological Functions. Int J Mol Sci 2023; 24:3407. [PMID: 36834817 PMCID: PMC9967218 DOI: 10.3390/ijms24043407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 01/18/2023] [Accepted: 01/21/2023] [Indexed: 02/11/2023] Open
Abstract
BK channels are large conductance potassium channels characterized by four pore-forming α subunits, often co-assembled with auxiliary β and γ subunits to regulate Ca2+ sensitivity, voltage dependence and gating properties. BK channels are abundantly expressed throughout the brain and in different compartments within a single neuron, including axons, synaptic terminals, dendritic arbors, and spines. Their activation produces a massive efflux of K+ ions that hyperpolarizes the cellular membrane. Together with their ability to detect changes in intracellular Ca2+ concentration, BK channels control neuronal excitability and synaptic communication through diverse mechanisms. Moreover, increasing evidence indicates that dysfunction of BK channel-mediated effects on neuronal excitability and synaptic function has been implicated in several neurological disorders, including epilepsy, fragile X syndrome, mental retardation, and autism, as well as in motor and cognitive behavior. Here, we discuss current evidence highlighting the physiological importance of this ubiquitous channel in regulating brain function and its role in the pathophysiology of different neurological disorders.
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Affiliation(s)
- Carlos Ancatén-González
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso 2340000, Chile
- Programa de Doctorado en Ciencias, Mención Neurociencia, Universidad de Valparaíso, Valparaíso 2340000, Chile
| | - Ignacio Segura
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso 2340000, Chile
| | - Rosangelina Alvarado-Sánchez
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso 2340000, Chile
- Doctorado en Ciencias Mención Biofísica y Biología Computacional, Universidad de Valparaíso, Valparaíso 2340000, Chile
| | - Andrés E. Chávez
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso 2340000, Chile
| | - Ramon Latorre
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso 2340000, Chile
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4
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Meza RC, Ancatén-González C, Chiu CQ, Chávez AE. Transient Receptor Potential Vanilloid 1 Function at Central Synapses in Health and Disease. Front Cell Neurosci 2022; 16:864828. [PMID: 35518644 PMCID: PMC9062234 DOI: 10.3389/fncel.2022.864828] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 03/29/2022] [Indexed: 12/11/2022] Open
Abstract
The transient receptor potential vanilloid 1 (TRPV1), a ligand-gated nonselective cation channel, is well known for mediating heat and pain sensation in the periphery. Increasing evidence suggests that TRPV1 is also expressed at various central synapses, where it plays a role in different types of activity-dependent synaptic changes. Although its precise localizations remain a matter of debate, TRPV1 has been shown to modulate both neurotransmitter release at presynaptic terminals and synaptic efficacy in postsynaptic compartments. In addition to being required in these forms of synaptic plasticity, TRPV1 can also modify the inducibility of other types of plasticity. Here, we highlight current evidence of the potential roles for TRPV1 in regulating synaptic function in various brain regions, with an emphasis on principal mechanisms underlying TRPV1-mediated synaptic plasticity and metaplasticity. Finally, we discuss the putative contributions of TRPV1 in diverse brain disorders in order to expedite the development of next-generation therapeutic treatments.
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Affiliation(s)
- Rodrigo C Meza
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Carlos Ancatén-González
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile.,Programa de Doctorado en Ciencias, Mención Neurociencia, Universidad de Valparaíso, Valparaíso, Chile
| | - Chiayu Q Chiu
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Andrés E Chávez
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile
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5
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Fuenzalida M, Chiu CQ, Chávez AE. Muscarinic Regulation of Spike Timing Dependent Synaptic Plasticity in the Hippocampus. Neuroscience 2020; 456:50-59. [PMID: 32828940 DOI: 10.1016/j.neuroscience.2020.08.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 08/01/2020] [Accepted: 08/11/2020] [Indexed: 11/18/2022]
Abstract
Long-term changes in synaptic transmission between neurons in the brain are considered the cellular basis of learning and memory. Over the last few decades, many studies have revealed that the precise order and timing of activity between pre- and post-synaptic cells ("spike-timing-dependent plasticity; STDP") is crucial for the sign and magnitude of long-term changes at many central synapses. Acetylcholine (ACh) via the recruitment of diverse muscarinic receptors is known to influence STDP in a variety of ways, enabling flexibility and adaptability in brain network activity during complex behaviors. In this review, we will summarize and discuss different mechanistic aspects of muscarinic modulation of timing-dependent plasticity at both excitatory and inhibitory synapses in the hippocampus to shape learning and memory.
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Affiliation(s)
- Marco Fuenzalida
- Center of Neurobiology and Integrative Physiopathology, Institute of Physiology, Faculty of Science, Universidad de Valparaíso, Chile.
| | - Chiayu Q Chiu
- Interdisciplinary Center of Neuroscience of Valparaiso, Institute of Neuroscience, Faculty of Science, Universidad de Valparaíso, Chile
| | - Andrés E Chávez
- Interdisciplinary Center of Neuroscience of Valparaiso, Institute of Neuroscience, Faculty of Science, Universidad de Valparaíso, Chile
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Vielma AH, Tapia F, Alcaino A, Fuenzalida M, Schmachtenberg O, Chávez AE. Cannabinoid Signaling Selectively Modulates GABAergic Inhibitory Input to OFF Bipolar Cells in Rat Retina. Invest Ophthalmol Vis Sci 2020; 61:3. [PMID: 32150246 PMCID: PMC7401570 DOI: 10.1167/iovs.61.3.3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose In the mammalian retina, cannabinoid type 1 receptors (CB1Rs) are well-positioned to alter inhibitory synaptic function from amacrine cells and, thus, might influence visual signal processing in the inner retina. However, it is not known if CB1R modulates amacrine cells feedback inhibition at retinal bipolar cell (BC) terminals. Methods Using whole-cell voltage-clamp recordings, we examined the pharmacological effect of CB1R activation and inhibition on spontaneous inhibitory postsynaptic currents (sIPSCs) and glutamate-evoked IPSCs (gIPSCs) from identified OFF BCs in light-adapted rat retinal slices. Results Activation of CB1R with WIN55212-2 selectively increased the frequency of GABAergic, but not glycinergic sIPSC in types 2, 3a, and 3b OFF BCs, and had no effect on inhibitory activity in type 4 OFF BCs. The increase in GABAergic activity was eliminated in axotomized BCs and can be suppressed by blocking CB1R with AM251 or GABAA and GABAρ receptors with SR-95531 and TPMPA, respectively. In all OFF BC types tested, a brief application of glutamate to the outer plexiform layer elicited gIPSCs comprising GABAergic and glycinergic components that were unaffected by CB1R activation. However, blocking CB1R selectively increased GABAergic gIPSCs, supporting a role for endocannabinoid signaling in the regulation of glutamate-evoked GABAergic inhibitory feedback to OFF BCs. Conclusions CB1R activation shape types 2, 3a, and 3b OFF BC responses by selectively regulate GABAergic feedback inhibition at their axon terminals, thus cannabinoid signaling might play an important role in the fine-tuning of visual signal processing in the mammalian inner retina.
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Plaza-Briceño W, Estay SF, de la Fuente-Ortega E, Gutiérrez C, Sánchez G, Hidalgo C, Chávez AE, Haeger PA. N-Methyl-d-Aspartate Receptor Modulation by Nicotinamide Adenine Dinucleotide Phosphate Oxidase Type 2 Drives Synaptic Plasticity and Spatial Memory Impairments in Rats Exposed Pre- and Postnatally to Ethanol. Antioxid Redox Signal 2020; 32:602-617. [PMID: 31880947 DOI: 10.1089/ars.2019.7787] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Aims: Pre- and/or early postnatal ethanol exposure (prenatal alcohol exposure [PAE]) impairs synaptic plasticity as well as memory formation, but the mechanisms underlying these effects remain unclear. Both long-term potentiation (LTP) and spatial memory formation in the hippocampus involve the nicotinamide adenine dinucleotide phosphate oxidase type 2 (NOX2) enzyme. Previous studies have reported that N-methyl-d-aspartate receptor (NMDAR) activation increases NOX2-mediated superoxide generation, resulting in inhibition of NMDAR function, but whether NOX2 impacts NMDAR function in PAE animals leading to impaired LTP and memory formation remains unknown. We aim to evaluate whether the NOX2-NMDAR complex is involved in the long-lasting deleterious effects of PAE on hippocampal LTP and memory formation. Results: Here we provide novel evidence that PAE animals display impaired NMDAR-dependent LTP in the cornus ammonis field 1 (CA1) and NMDAR-mediated LTP in the dentate gyrus (DG). Moreover, PAE rats displayed increased NMDAR-mediated transmission in both hippocampal areas. Interestingly, NOX2 pharmacological inhibition restored NMDAR-mediated transmission and LTP in the CA1, but not in the DG. PAE also induced overexpression of NOX2 and CaMKII isoforms, but did not modify the content or the redox state of the N-methyl-d-aspartate receptor subunit-1 (NR1) subunit of NMDAR in both areas of the hippocampus. In addition, adolescent PAE rats orally fed the antioxidant and free radical scavenger apocynin exhibited significantly improved spatial memory acquisition. Innovation and Conclusion: By showing in PAE animals NOX2 overexpression and increased NMDAR-mediated transmission, which might lead to impaired synaptic plasticity and memory formation in a region-specific manner, we provide an important advance to our current understanding of the cellular mechanisms underlying PAE-dependent defective hippocampal function.
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Affiliation(s)
- Wladimir Plaza-Briceño
- Departamento de Ciencias Biomédicas, Facultad De Medicina, Universidad Católica Del Norte, Coquimbo, Chile.,Programa de Magíster en Ciencias Biológicas mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaiso, Chile
| | - Sebastián F Estay
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile.,Programa de Doctorado en Ciencias mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaiso, Chile
| | - Erwin de la Fuente-Ortega
- Departamento de Ciencias Biomédicas, Facultad De Medicina, Universidad Católica Del Norte, Coquimbo, Chile
| | - Camilo Gutiérrez
- Departamento de Ciencias Biomédicas, Facultad De Medicina, Universidad Católica Del Norte, Coquimbo, Chile
| | - Gina Sánchez
- Programa de Fisiopatología, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, Santiago, Chile.,CEMC, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Cecilia Hidalgo
- CEMC, Facultad de Medicina, Universidad de Chile, Santiago, Chile.,Biomedical Neuroscience Institute, Facultad de Medicina, Universidad de Chile, Santiago, Chile.,Departamento de Neurociencia, Facultad de Medicina, Universidad de Chile, Santiago, Chile.,Programa de Fisiología y Biofísica, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Andrés E Chávez
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Paola A Haeger
- Departamento de Ciencias Biomédicas, Facultad De Medicina, Universidad Católica Del Norte, Coquimbo, Chile
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8
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Espinosa N, Alonso A, Morales C, Espinosa P, Chávez AE, Fuentealba P. Basal Forebrain Gating by Somatostatin Neurons Drives Prefrontal Cortical Activity. Cereb Cortex 2020; 29:42-53. [PMID: 29161383 DOI: 10.1093/cercor/bhx302] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The basal forebrain provides modulatory input to the cortex regulating brain states and cognitive processing. Somatostatin-expressing neurons constitute a heterogeneous GABAergic population known to functionally inhibit basal forebrain cortically projecting cells thus favoring sleep and cortical synchronization. However, it remains unclear if somatostatin cells can regulate population activity patterns in the basal forebrain and modulate cortical dynamics. Here, we demonstrate that somatostatin neurons regulate the corticopetal synaptic output of the basal forebrain impinging on cortical activity and behavior. Optogenetic inactivation of somatostatin neurons in vivo rapidly modified neural activity in the basal forebrain, with the consequent enhancement and desynchronization of activity in the prefrontal cortex, reflected in both neuronal spiking and network oscillations. Cortical activation was partially dependent on cholinergic transmission, suppressing slow waves and potentiating gamma oscillations. In addition, recruitment dynamics was cell type-specific, with interneurons showing similar temporal profiles, but stronger responses than pyramidal cells. Finally, optogenetic stimulation of quiescent animals during resting periods prompted locomotor activity, suggesting generalized cortical activation and increased arousal. Altogether, we provide physiological and behavioral evidence indicating that somatostatin neurons are pivotal in gating the synaptic output of the basal forebrain, thus indirectly controlling cortical operations via both cholinergic and non-cholinergic mechanisms.
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Affiliation(s)
- Nelson Espinosa
- Departamento de Psiquiatria, Centro Interdisciplinario de Neurociencia UC,Pontificia Universidad Catolica de Chile, Marcoleta 391, Santiago, Chile
| | - Alejandra Alonso
- Departamento de Psiquiatria, Centro Interdisciplinario de Neurociencia UC,Pontificia Universidad Catolica de Chile, Marcoleta 391, Santiago, Chile
| | - Cristian Morales
- Departamento de Psiquiatria, Centro Interdisciplinario de Neurociencia UC,Pontificia Universidad Catolica de Chile, Marcoleta 391, Santiago, Chile
| | - Pedro Espinosa
- Centro Interdisciplinario de Neurociencia de Valparaíso and Núcleo Milenio Biología de Enfermedades Neuropsiquiátricas, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Andrés E Chávez
- Centro Interdisciplinario de Neurociencia de Valparaíso and Núcleo Milenio Biología de Enfermedades Neuropsiquiátricas, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Pablo Fuentealba
- Departamento de Psiquiatria, Centro Interdisciplinario de Neurociencia UC,Pontificia Universidad Catolica de Chile, Marcoleta 391, Santiago, Chile.,Centro de Investigación en Nanotecnología y Materiales Avanzados CIEN-UC, Pontificia Universidad Catolica de Chile, Avenida Vicuña Mackenna 4860, Macul, Santiago, Chile
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9
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Escobar AP, Wendland JR, Chávez AE, Moya PR. The Neuronal Glutamate Transporter EAAT3 in Obsessive-Compulsive Disorder. Front Pharmacol 2019; 10:1362. [PMID: 31803055 PMCID: PMC6872633 DOI: 10.3389/fphar.2019.01362] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Accepted: 10/28/2019] [Indexed: 01/03/2023] Open
Abstract
Obsessive compulsive disorder (OCD) is a heterogeneous psychiatric disorder affecting 1%–3% of the population worldwide. About half of OCD afflicted individuals do not respond to currently available pharmacotherapy, which is mainly based on serotonin reuptake inhibition. Therefore, there is a critical need to search novel and improved therapeutic targets to treat this devastating disorder. In recent years, accumulating evidence has supported the glutamatergic hypothesis of OCD, and particularly pointing a potential role for the neuronal glutamate transporter EAAT3. This mini-review summarizes recent findings regarding the neurobiological basis of OCD, with an emphasis on the glutamatergic neurotransmission and EAAT3 as a key player in OCD etiology.
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Affiliation(s)
- Angélica P Escobar
- Centro Interdisciplinario de Neurociencia de Valparaíso CINV, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Jens R Wendland
- Centro Interdisciplinario de Neurociencia de Valparaíso CINV, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Andrés E Chávez
- Centro Interdisciplinario de Neurociencia de Valparaíso CINV, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Pablo R Moya
- Centro Interdisciplinario de Neurociencia de Valparaíso CINV, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile.,Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Valparaiso, Chile
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Hashimotodani Y, Nasrallah K, Jensen KR, Chávez AE, Carrera D, Castillo PE. LTP at Hilar Mossy Cell-Dentate Granule Cell Synapses Modulates Dentate Gyrus Output by Increasing Excitation/Inhibition Balance. Neuron 2017; 95:928-943.e3. [PMID: 28817805 PMCID: PMC5609819 DOI: 10.1016/j.neuron.2017.07.028] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Revised: 06/23/2017] [Accepted: 07/25/2017] [Indexed: 01/20/2023]
Abstract
Excitatory hilar mossy cells (MCs) in the dentate gyrus receive inputs from dentate granule cells (GCs) and project back to GCs locally, contralaterally, and along the longitudinal axis of the hippocampus, thereby establishing an associative positive-feedback loop and connecting functionally diverse hippocampal areas. MCs also synapse with GABAergic interneurons that mediate feed-forward inhibition onto GCs. Surprisingly, although these circuits have been implicated in both memory formation (e.g., pattern separation) and temporal lobe epilepsy, little is known about activity-dependent plasticity of their synaptic connections. Here, we report that MC-GC synapses undergo a presynaptic, NMDA-receptor-independent form of long-term potentiation (LTP) that requires postsynaptic brain-derived neurotrophic factor (BDNF)/TrkB and presynaptic cyclic AMP (cAMP)/PKA signaling. This LTP is input specific and selectively expressed at MC-GC synapses, but not at the disynaptic inhibitory loop. By increasing the excitation/inhibition balance, MC-GC LTP enhances GC output at the associative MC-GC recurrent circuit and may contribute to dentate-dependent forms of learning and epilepsy.
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Affiliation(s)
- Yuki Hashimotodani
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Kaoutsar Nasrallah
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Kyle R Jensen
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Andrés E Chávez
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Daniel Carrera
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Pablo E Castillo
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
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Park J, Chávez AE, Mineur YS, Morimoto-Tomita M, Lutzu S, Kim KS, Picciotto MR, Castillo PE, Tomita S. CaMKII Phosphorylation of TARPγ-8 Is a Mediator of LTP and Learning and Memory. Neuron 2016; 92:75-83. [PMID: 27667007 DOI: 10.1016/j.neuron.2016.09.002] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2015] [Revised: 06/25/2016] [Accepted: 08/29/2016] [Indexed: 11/28/2022]
Abstract
Protein phosphorylation is an essential step for the expression of long-term potentiation (LTP), a long-lasting, activity-dependent strengthening of synaptic transmission widely regarded as a cellular mechanism underlying learning and memory. At the core of LTP is the synaptic insertion of AMPA receptors (AMPARs) triggered by the NMDA receptor-dependent activation of Ca2+/calmodulin-dependent protein kinase II (CaMKII). However, the CaMKII substrate that increases AMPAR-mediated transmission during LTP remains elusive. Here, we identify the hippocampus-enriched TARPγ-8, but not TARPγ-2/3/4, as a critical CaMKII substrate for LTP. We found that LTP induction increases TARPγ-8 phosphorylation, and that CaMKII-dependent enhancement of AMPAR-mediated transmission requires CaMKII phosphorylation sites of TARPγ-8. Moreover, LTP and memory formation, but not basal transmission, are significantly impaired in mice lacking CaMKII phosphorylation sites of TARPγ-8. Together, these findings demonstrate that TARPγ-8 is a crucial mediator of CaMKII-dependent LTP and therefore a molecular target that controls synaptic plasticity and associated cognitive functions.
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Affiliation(s)
- Joongkyu Park
- Department of Cellular and Molecular Physiology, Program in Cellular Neuroscience, Neurodegeneration, and Repair, Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06520, USA; Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Andrés E Chávez
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA; Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2340000, Chile
| | - Yann S Mineur
- Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, CT 06520, USA; Department of Psychiatry, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Megumi Morimoto-Tomita
- Department of Cellular and Molecular Physiology, Program in Cellular Neuroscience, Neurodegeneration, and Repair, Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06520, USA; Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Stefano Lutzu
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Kwang S Kim
- Department of Cellular and Molecular Physiology, Program in Cellular Neuroscience, Neurodegeneration, and Repair, Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06520, USA; Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Marina R Picciotto
- Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, CT 06520, USA; Department of Psychiatry, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Pablo E Castillo
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| | - Susumu Tomita
- Department of Cellular and Molecular Physiology, Program in Cellular Neuroscience, Neurodegeneration, and Repair, Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06520, USA; Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, CT 06520, USA.
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Kalinowska M, Chávez AE, Lutzu S, Castillo PE, Bukauskas FF, Francesconi A. Actinin-4 Governs Dendritic Spine Dynamics and Promotes Their Remodeling by Metabotropic Glutamate Receptors. J Biol Chem 2015; 290:15909-20. [PMID: 25944910 DOI: 10.1074/jbc.m115.640136] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Indexed: 11/06/2022] Open
Abstract
Dendritic spines are dynamic, actin-rich protrusions in neurons that undergo remodeling during neuronal development and activity-dependent plasticity within the central nervous system. Although group 1 metabotropic glutamate receptors (mGluRs) are critical for spine remodeling under physiopathological conditions, the molecular components linking receptor activity to structural plasticity remain unknown. Here we identify a Ca(2+)-sensitive actin-binding protein, α-actinin-4, as a novel group 1 mGluR-interacting partner that orchestrates spine dynamics and morphogenesis in primary neurons. Functional silencing of α-actinin-4 abolished spine elongation and turnover stimulated by group 1 mGluRs despite intact surface receptor expression and downstream ERK1/2 signaling. This function of α-actinin-4 in spine dynamics was underscored by gain-of-function phenotypes in untreated neurons. Here α-actinin-4 induced spine head enlargement, a morphological change requiring the C-terminal domain of α-actinin-4 that binds to CaMKII, an interaction we showed to be regulated by group 1 mGluR activation. Our data provide mechanistic insights into spine remodeling by metabotropic signaling and identify α-actinin-4 as a critical effector of structural plasticity within neurons.
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Affiliation(s)
- Magdalena Kalinowska
- From the Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Andrés E Chávez
- From the Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Stefano Lutzu
- From the Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Pablo E Castillo
- From the Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Feliksas F Bukauskas
- From the Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Anna Francesconi
- From the Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461
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Abstract
Endocannabinoids are key modulators of synaptic function. By activating cannabinoid receptors expressed in the central nervous system, these lipid messengers can regulate several neural functions and behaviors. As experimental tools advance, the repertoire of known endocannabinoid-mediated effects at the synapse, and their underlying mechanism, continues to expand. Retrograde signaling is the principal mode by which endocannabinoids mediate short- and long-term forms of plasticity at both excitatory and inhibitory synapses. However, growing evidence suggests that endocannabinoids can also signal in a nonretrograde manner. In addition to mediating synaptic plasticity, the endocannabinoid system is itself subject to plastic changes. Multiple points of interaction with other neuromodulatory and signaling systems have now been identified. In this Review, we focus on new advances in synaptic endocannabinoid signaling in the mammalian brain. The emerging picture not only reinforces endocannabinoids as potent regulators of synaptic function but also reveals that endocannabinoid signaling is mechanistically more complex and diverse than originally thought.
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Affiliation(s)
- Pablo E Castillo
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
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Rodenas-Ruano A, Chávez AE, Cossio MJ, Castillo PE, Zukin RS. REST-dependent epigenetic remodeling promotes the developmental switch in synaptic NMDA receptors. Nat Neurosci 2012; 15:1382-90. [PMID: 22960932 PMCID: PMC3501125 DOI: 10.1038/nn.3214] [Citation(s) in RCA: 154] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Accepted: 08/13/2012] [Indexed: 11/20/2022]
Abstract
N-methyl-D-aspartate receptors (NMDARs) are critical to synaptogenesis, neural circuitry and higher cognitive functions such as learning and memory. A hallmark feature of NMDARs is an early postnatal developmental switch from primarily GluN2B- to GluN2A-containing. Although the switch in phenotype has been an area of intense interest for two decades, the mechanisms that trigger it, and the link between experience and the switch are unclear. Here we show a novel role for the transcriptional repressor REST in the developmental switch of synaptic NMDARs. REST is activated at a critical window of time and acts via epigenetic remodeling to repress grin2b expression and properties at rat hippocampal synapses. Knockdown of REST in vivo prevented the decline in GluN2B and developmental switch in NMDARs. Notably, maternal deprivation impaired REST activation and acquisition of the mature NMDAR phenotype. Thus, REST is essential for experience-dependent fine-tuning of genes involved in synaptic plasticity.
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Affiliation(s)
- Alma Rodenas-Ruano
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York, USA
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Kaeser PS, Deng L, Chávez AE, Liu X, Castillo PE, Südhof TC. ELKS2alpha/CAST deletion selectively increases neurotransmitter release at inhibitory synapses. Neuron 2009; 64:227-39. [PMID: 19874790 PMCID: PMC2785857 DOI: 10.1016/j.neuron.2009.09.019] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/24/2009] [Indexed: 11/26/2022]
Abstract
The presynaptic active zone is composed of a protein network that contains ELKS2alpha (a.k.a. CAST) as a central component. Here we demonstrate that in mice, deletion of ELKS2alpha caused a large increase in inhibitory, but not excitatory, neurotransmitter release, and potentiated the size, but not the properties, of the readily-releasable pool of vesicles at inhibitory synapses. Quantitative electron microscopy revealed that the ELKS2alpha deletion did not change the number of docked vesicles or other ultrastructural parameters of synapses, except for a small decrease in synaptic vesicle numbers. The ELKS2alpha deletion did, however, alter the excitatory/inhibitory balance and exploratory behaviors, possibly as a result of the increased synaptic inhibition. Thus, as opposed to previous studies indicating that ELKS2alpha is essential for mediating neurotransmitter release, our results suggest that ELKS2alpha normally restricts release and limits the size of the readily-releasable pool of synaptic vesicles at the active zone of inhibitory synapses.
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Affiliation(s)
- Pascal S Kaeser
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Palo Alto, CA 94304-5543, USA
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Chávez AE, Singer JH, Diamond JS. Fast neurotransmitter release triggered by Ca influx through AMPA-type glutamate receptors. Nature 2006; 443:705-8. [PMID: 17036006 DOI: 10.1038/nature05123] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2006] [Accepted: 07/31/2006] [Indexed: 11/08/2022]
Abstract
Feedback inhibition at reciprocal synapses between A17 amacrine cells and rod bipolar cells (RBCs) shapes light-evoked responses in the retina. Glutamate-mediated excitation of A17 cells elicits GABA (gamma-aminobutyric acid)-mediated inhibitory feedback onto RBCs, but the mechanisms that underlie GABA release from the dendrites of A17 cells are unknown. If, as observed at all other synapses studied, voltage-gated calcium channels (VGCCs) couple membrane depolarization to neurotransmitter release, feedforward excitatory postsynaptic potentials could spread through A17 dendrites to elicit 'surround' feedback inhibitory transmission at neighbouring synapses. Here we show, however, that GABA release from A17 cells in the rat retina does not depend on VGCCs or membrane depolarization. Instead, calcium-permeable AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptors (AMPARs), activated by glutamate released from RBCs, provide the calcium influx necessary to trigger GABA release from A17 cells. The AMPAR-mediated calcium signal is amplified by calcium-induced calcium release (CICR) from intracellular calcium stores. These results describe a fast synapse that operates independently of VGCCs and membrane depolarization and reveal a previously unknown form of feedback inhibition within a neural circuit.
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Affiliation(s)
- Andrés E Chávez
- Synaptic Physiology Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892-3701, USA
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Chávez AE, Pannicke T, Roncagliolo M, Reichenbach A, Palacios AG. Electrophysiological properties of retinal Müller glial cells from myelin mutant rat. Glia 2003; 45:338-45. [PMID: 14966865 DOI: 10.1002/glia.10330] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The structural and functional similarities between Müller cells and oligodendrocytes prompted the present study of the electrophysiological properties of Müller (glia) cells obtained from the retinae of control and myelin mutant taiep rats during the postnatal developmental period (P12-P180). The whole-cell configuration of the patch-clamp technique was used to characterize the general properties and the K+ currents from dissociated Müller cells. During the first 3 weeks of life, a decrease of the membrane resistance and an increase of the membrane potential were observed in Müller cells from both control and taiep rats. However, Müller cells from taiep rats never achieved the very negative membrane potential (-50 mV vs -80 mV) and the low membrane resistance characteristic for control cells. Furthermore, Müller cells displayed increased inward and outward K+ currents during postnatal development up to P30/60 in controls; however, in taiep rats, this increase ceased at P20/30, and low-amplitude currents persisted into adulthood. These results provide first evidence of physiological changes in retinal Müller cells as a consequence of a myelin mutation causing a progressive deterioration of the central nervous system (CNS) due to a disturbance of the microtubule network of oligodendrocytes. We hypothesize that the progressive dysmyelination process of the optic nerve, accompanied by functional deficits of retinal neurons (e.g., ganglion cells), induces physiological alterations of Müller cells.
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Affiliation(s)
- Andrés E Chávez
- Department of Physiology, Faculty of Science, Neuroscience Center of Valparaiso, University of Valparaíso, Valparaíso, Chile
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Chávez AE, Bozinovic F, Peichl L, Palacios AG. Retinal spectral sensitivity, fur coloration, and urine reflectance in the genus octodon (rodentia): implications for visual ecology. Invest Ophthalmol Vis Sci 2003; 44:2290-6. [PMID: 12714673 DOI: 10.1167/iovs.02-0670] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To determine the eye's spectral sensitivity in three species of the genus Octodon (order Rodentia; infraorder Caviomorpha), O. degus, O. bridgesi, and O. lunatus, as well as the spectral properties of the animals' fur and urine and of objects in their habitat. The genus is endemic in Chile and contains species with different habitats and circadian patterns (diurnal versus nocturnal). METHODS The electroretinogram (ERG) was used to record scotopic and photopic spectral sensitivity. The reflectance of ventral and dorsal body parts, urine, and other objects from the natural microhabitat were measured with a fiber-optic spectrometer. RESULTS In scotopic conditions, the maxima of sensitivity (lambda(max)) were at 505.7 +/- 7.7 nm in O. degus, 501 +/- 7.4 nm in O. bridgesi, and 510.1 +/- 7.4 nm in O. lunatus, representing the rod mechanism. In photopic conditions, only the diurnal species O. degus (common degu) was studied. The degu's photopic sensitivity had a lambda(max) at 500.6 +/- 1.2 nm and contained two cone mechanisms with lambda(max) at 500 nm (green, medium-wavelength-sensitive [M] cones) and approximately 360 nm (ultraviolet, short-wavelength-sensitive [S] cones). In all three Octodon species, dorsal body parts were more cryptically colored than ventral ones, and ventral body parts had a significant UV reflectance. The fresh urine of O. degus, used for scent marking in various behavioral patterns, was also high in UV reflectance. CONCLUSIONS It is suggested that territorial urine marks are visual as well as pheromone cues for UV-sensitive species and hence may have favored the evolution of UV-cones in rodents.
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Affiliation(s)
- Andrés E Chávez
- Department of Physiology, Faculty of Science and Center of Molecular and Cellular Neuroscience of Valparaíso, University of Valparaíso, Valparaíso, Chile
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Abstract
PURPOSE To study the histology and the physiological function of the retina in the neurological myelin mutant, taiep rats during the postnatal developmental period (P20-P360). METHODS Electroretinography (ERG) was applied to evaluate intensity dependence and spectral sensitivity of the responses to light. Retinal histology, morphometry, and immunocytochemistry were used to characterize the structure of the retina, with particular emphasis on the Müller (glial) cells. RESULTS In the taiep rats of all ages studied, the scotopic ERG showed normal a- and b-wave amplitudes and latencies; likewise, the scotopic spectral sensitivity function was the same for control and taiep animals, with a maximal sensitivity (lambda(max)) at 500 nm. However, in adult taiep rats (P90 to P360) a secondary cornea-positive wave ('b(2)') was observed in response to high stimulus intensities, which never occurred in controls. This correlated with the observation that in the photopic ERG responses of the taiep rats, the b-wave was reduced in amplitude, and was followed by a rapid cornea-negative after-potential. After 1 year of life, in taiep rats the outer plexiform layer (OPL) became slightly thinner and the inner plexiform/ganglion cell layers (IPL/GCL) appeared to be swollen, and increased in thickness; in addition, the number of retinal neurons (particularly, of photoreceptor cells) slightly decreased. Increased GFAP immunoreactivity revealed a hypertrophy and reactivity of the Müller cells in 1-year-old taiep rats. CONCLUSIONS The present results suggest the occurrence of a relatively mild and slowly progressing neural retinal alteration in taiep rats, which becomes histologically and functionally evident at the end of the first year of life, and mainly affects the circuit(s) of the photopic ON-response. It is speculated that this alteration is due to missing/altered signals from demyelinated optic nerve.
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Affiliation(s)
- Andrés E Chávez
- Molecular Cellular Center for Neuroscience of Valparaiso, Faculty of Science, University of Valparaíso, P.O. Box 5030, Valparaíso, Chile
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Abstract
Although plastic surgeons are increasingly incorporating computer imaging techniques into their practices, many fear the possibility of legally binding themselves to achieve surgical results identical to those reflected in computer images. Computer imaging allows surgeons to manipulate digital photographs of patients to project possible surgical outcomes. Some of the many benefits imaging techniques pose include improving doctor-patient communication, facilitating the education and training of residents, and reducing administrative and storage costs. Despite the many advantages computer imaging systems offer, however, surgeons understandably worry that imaging systems expose them to immense legal liability. The possible exploitation of computer imaging by novice surgeons as a marketing tool, coupled with the lack of consensus regarding the treatment of computer images, adds to the concern of surgeons. A careful analysis of the law, however, reveals that surgeons who use computer imaging carefully and conservatively, and adopt a few simple precautions, substantially reduce their vulnerability to legal claims. In particular, surgeons face possible claims of implied contract, failure to instruct, and malpractice from their use or failure to use computer imaging. Nevertheless, legal and practical obstacles frustrate each of those causes of actions. Moreover, surgeons who incorporate a few simple safeguards into their practice may further reduce their legal susceptibility.
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Affiliation(s)
- A E Chávez
- Stanford Law School, Stanford University, Calif., USA
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