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Abstract
In neurons, microtubules (MTs) provide routes for transport throughout the cell and structural support for dendrites and axons. Both stable and dynamic MTs are necessary for normal neuronal functions. Research in the last two decades has demonstrated that MTs play additional roles in synaptic structure and function in both pre- and postsynaptic elements. Here, we review current knowledge of the functions that MTs perform in excitatory and inhibitory synapses, as well as in the neuromuscular junction and other specialized synapses, and discuss the implications that this knowledge may have in neurological disease.
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Affiliation(s)
- Julie Parato
- Columbia University Medical Center, Department of Pathology & Cell Biology, 630 West 168(th)Street, P&S 15-421, NY, NY, 10032, United States; SUNY Empire State College, Department of Natural Sciences, 177 Livingston Street, Brooklyn, NY, 11201, United States
| | - Francesca Bartolini
- Columbia University Medical Center, Department of Pathology & Cell Biology, 630 West 168(th)Street, P&S 15-421, NY, NY, 10032, United States.
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Perez-Rando M, Castillo-Gomez E, Bueno-Fernandez C, Nacher J. The TrkB agonist 7,8-dihydroxyflavone changes the structural dynamics of neocortical pyramidal neurons and improves object recognition in mice. Brain Struct Funct 2018; 223:2393-2408. [PMID: 29500536 DOI: 10.1007/s00429-018-1637-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [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: 11/17/2017] [Accepted: 02/20/2018] [Indexed: 01/17/2023]
Abstract
BDNF and its receptor TrkB have important roles in neurodevelopment, neural plasticity, learning, and memory. Alterations in TrkB expression have been described in different CNS disorders. Therefore, drugs interacting with TrkB, specially agonists, are promising therapeutic tools. Among them, the recently described 7,8-dihydroxyflavone (DHF), an orally bioactive compound, has been successfully tested in animal models of these diseases. Recent studies have shown the influence of this drug on the structure of pyramidal neurons, specifically on dendritic spine density. However, there is no information yet on how DHF may alter the structural dynamics of these neurons (i.e., real-time study of the addition/elimination of dendritic spines and axonal boutons). To gain knowledge on these effects of DHF, we have performed a real-time analysis of spine and axonal dynamics in pyramidal neurons of barrel cortex, using cranial windows and 2-photon microscopy during a chronic oral treatment with this drug. After confirming TrkB expression in these neurons, we found that DHF increased the gain rates of spines and axonal boutons, as well as improved object recognition memory. These results help to understand how the activation of the BDNF-TrkB system can improve basic behavioral tasks through changes in the structural dynamics of pyramidal neurons. Moreover, they highlight DHF as a promising therapeutic vector for certain brain disorders in which this system is altered.
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Affiliation(s)
- Marta Perez-Rando
- Neurobiology Unit, Cell Biology Department, Program in Neurosciences and Interdisciplinary Research Structure for Biotechnology and Biomedicine (BIOTECMED), Universitat de València, Dr. Moliner, 50, Burjassot, 46100, Spain
| | - Esther Castillo-Gomez
- Neurobiology Unit, Cell Biology Department, Program in Neurosciences and Interdisciplinary Research Structure for Biotechnology and Biomedicine (BIOTECMED), Universitat de València, Dr. Moliner, 50, Burjassot, 46100, Spain. .,CIBERSAM: Spanish National Network for Research in Mental Health, Valencia, Spain. .,Department of Medicine, School of Medical Sciences, Universitat Jaume I, Vicente Sos Banyat s/n, 12071, Castellón de la Plana, Spain.
| | - Clara Bueno-Fernandez
- Neurobiology Unit, Cell Biology Department, Program in Neurosciences and Interdisciplinary Research Structure for Biotechnology and Biomedicine (BIOTECMED), Universitat de València, Dr. Moliner, 50, Burjassot, 46100, Spain
| | - Juan Nacher
- Neurobiology Unit, Cell Biology Department, Program in Neurosciences and Interdisciplinary Research Structure for Biotechnology and Biomedicine (BIOTECMED), Universitat de València, Dr. Moliner, 50, Burjassot, 46100, Spain. .,CIBERSAM: Spanish National Network for Research in Mental Health, Valencia, Spain. .,Fundación Investigación Hospital Clínico de Valencia, INCLIVA, Valencia, Spain.
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Tao J, Bulgari D, Deitcher DL, Levitan ES. Limited distal organelles and synaptic function in extensive monoaminergic innervation. J Cell Sci 2017; 130:2520-2529. [PMID: 28600320 DOI: 10.1242/jcs.201111] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [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: 12/28/2016] [Accepted: 06/05/2017] [Indexed: 12/20/2022] Open
Abstract
Organelles such as neuropeptide-containing dense-core vesicles (DCVs) and mitochondria travel down axons to supply synaptic boutons. DCV distribution among en passant boutons in small axonal arbors is mediated by circulation with bidirectional capture. However, it is not known how organelles are distributed in extensive arbors associated with mammalian dopamine neuron vulnerability, and with volume transmission and neuromodulation by monoamines and neuropeptides. Therefore, we studied presynaptic organelle distribution in Drosophila octopamine neurons that innervate ∼20 muscles with ∼1500 boutons. Unlike in smaller arbors, distal boutons in these arbors contain fewer DCVs and mitochondria, although active zones are present. Absence of vesicle circulation is evident by proximal nascent DCV delivery, limited impact of retrograde transport and older distal DCVs. Traffic studies show that DCV axonal transport and synaptic capture are not scaled for extensive innervation, thus limiting distal delivery. Activity-induced synaptic endocytosis and synaptic neuropeptide release are also reduced distally. We propose that limits in organelle transport and synaptic capture compromise distal synapse maintenance and function in extensive axonal arbors, thereby affecting development, plasticity and vulnerability to neurodegenerative disease.
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Affiliation(s)
- Juan Tao
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Dinara Bulgari
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - David L Deitcher
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA
| | - Edwin S Levitan
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA
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Curto Y, Garcia-Mompo C, Bueno-Fernandez C, Nacher J. Chronic benzodiazepine treatment decreases spine density in cortical pyramidal neurons. Neurosci Lett 2016; 613:41-6. [PMID: 26733301 DOI: 10.1016/j.neulet.2015.12.048] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Revised: 12/18/2015] [Accepted: 12/21/2015] [Indexed: 01/26/2023]
Abstract
The adult brain retains a substantial capacity for synaptic reorganization, which includes a wide range of modifications from molecular to structural plasticity. Previous reports have demonstrated that the structural remodeling of excitatory neurons seems to occur in parallel to changes in GABAergic neurotransmission. The function of neuronal inhibitory networks can be modified through GABAA receptors, which have a binding site for benzodiazepines (BZ). Although BZs are among the most prescribed drugs, is not known whether they modify the structure and connectivity of pyramidal neurons. In the present study we wish to elucidate the impact of a chronic treatment of 21 days with diazepam (2mg/kg, ip), a BZ that acts as an agonist of GABAA receptors, on the structural plasticity of pyramidal neurons in the prefrontal cortex of adult mice. We have examined the density of dendritic spines and the density of axonal en passant boutons in the cingulate cortex. Although no significant changes were observed in their anxiety levels, animals treated with diazepam showed a decrease in the density of spines in the apical dendrites of pyramidal neurons. Most GFP-expressing en passant boutons in the upper layers of the cingulate cortex had an extracortical origin and no changes in their density were detected after diazepam treatment. These results indicate that the chronic potentiation of GABAergic synapses can induce the structural remodeling of postsynaptic elements in pyramidal neurons.
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