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Huang X, Lin Z, Wang K, Liu X, Zhou W, Meng L, Huang J, Yuan K, Niu L, Zheng H. Transcranial Low-Intensity Pulsed Ultrasound Modulates Structural and Functional Synaptic Plasticity in Rat Hippocampus. IEEE Trans Ultrason Ferroelectr Freq Control 2019; 66:930-938. [PMID: 30869615 DOI: 10.1109/tuffc.2019.2903896] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Plasticity of synaptic structure and function play an essential role in neuronal development, cognitive functions, and degenerative diseases. Recently, low-intensity pulsed ultrasound (LIPUS) stimulation has been reported as a promising technology for neuromodulation. However, the effect of LIPUS stimulation on the structural and functional synaptic plasticity in rat hippocampus has not yet been addressed. The aim of this study was to investigate whether LIPUS stimulation could affect the dendritic structure, electrophysiological properties, and expression level of glutamate receptors GluN2A, GluN2B, and GluR1 subunits in rat hippocampus. Transcranial LIPUS was delivered to CA1 of the intact hippocampus of rats ( n = 40 ) for 10 days (10 min/day) with the following parameters: fundamental frequency of 0.5 MHz, pulse repetition frequency (PRF) of 500 Hz, peak negative pressure of 0.42 MPa, and Ispta of 360 mW/cm2. The effect of LIPUS on dendritic structure, electrophysiological properties, and the expression of neurotransmitter receptors was measured using Golgi staining, electrophysiological recording, and western blotting, respectively. Golgi staining and electrophysiological recordings showed that LIPUS stimulation significantly increased the density of dendritic spines (0.72 ± 0.17 versus 0.94 ± 0.19 spines/ [Formula: see text], ) and the frequency of spontaneous excitatory postsynaptic current (0.37 ± 0.14 versus 1.77 ± 0.37 Hz, ) of CA1 hippocampal neurons. Furthermore, the western blotting analysis demonstrated a significant increase in the expression level of GluN2A ( ). The results illustrated the effect of LIPUS on the dendritic structure, function, and neurotransmitter receptors, which may provide a powerful tool for treating neurodegenerative diseases.
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Carr H, Alexander TC, Groves T, Kiffer F, Wang J, Price E, Boerma M, Allen AR. Early effects of 16O radiation on neuronal morphology and cognition in a murine model. Life Sci Space Res (Amst) 2018; 17:63-73. [PMID: 29753415 DOI: 10.1016/j.lssr.2018.03.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 02/23/2018] [Accepted: 03/02/2018] [Indexed: 06/08/2023]
Abstract
Astronauts exposed to high linear energy transfer radiation may experience cognitive injury. The pathogenesis of this injury is unknown but may involve glutamate receptors or modifications to dendritic structure and/or dendritic spine density and morphology. Glutamate is the major excitatory neurotransmitter in the central nervous system, where it acts on ionotropic and metabotropic glutamate receptors located at the presynaptic terminal and in the postsynaptic membrane at synapses in the hippocampus. Dendritic spines are sites of excitatory synaptic transmission, and changes in spine structure and dendrite morphology are thought to be morphological correlates of altered brain function associated with hippocampal-dependent learning and memory. The aim of the current study is to assess whether behavior, glutamate receptor gene expression, and dendritic structure in the hippocampus are altered in mice after early exposure to 16O radiation in mice. Two weeks post-irradiation, animals were tested for hippocampus-dependent cognitive performance in the Y-maze. During Y-maze testing, mice exposed to 0.1 Gy and 0.25 Gy radiation failed to distinguish the novel arm, spending approximately the same amount of time in all 3 arms during the retention trial. Exposure to 16O significantly reduced the expression of Nr1 and GluR1 in the hippocampus and modulated spine morphology in the dentate gyrus and cornu Ammon 1 within the hippocampus. The present data provide evidence that 16O radiation has early deleterious effects on mature neurons that are associated with hippocampal learning and memory.
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Affiliation(s)
- Hannah Carr
- Division of Radiation Health, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States.
| | - Tyler C Alexander
- Division of Radiation Health, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States; Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States.
| | - Thomas Groves
- Division of Radiation Health, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States; Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States; Neurobiology & Developmental Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States.
| | - Frederico Kiffer
- Division of Radiation Health, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States; Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States.
| | - Jing Wang
- Division of Radiation Health, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States; Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States.
| | - Elvin Price
- Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States.
| | - Marjan Boerma
- Division of Radiation Health, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States; Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States.
| | - Antiño R Allen
- Division of Radiation Health, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States; Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States; Neurobiology & Developmental Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States.
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Soler JE, Robison AJ, Núñez AA, Yan L. Light modulates hippocampal function and spatial learning in a diurnal rodent species: A study using male nile grass rat (Arvicanthis niloticus). Hippocampus 2017; 28:189-200. [PMID: 29251803 DOI: 10.1002/hipo.22822] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [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: 09/21/2017] [Revised: 11/09/2017] [Accepted: 12/14/2017] [Indexed: 01/05/2023]
Abstract
The effects of light on cognitive function have been well-documented in human studies, with brighter illumination improving cognitive performance in school children, healthy adults, and patients in early stages of dementia. However, the underlying neural mechanisms are not well understood. The present study examined how ambient light affects hippocampal function using the diurnal Nile grass rats (Arvicanthis niloticus) as the animal model. Grass rats were housed in either a 12:12 h bright light-dark (brLD, 1,000 lux) or dim light-dark (dimLD, 50 lux) cycle. After 4 weeks, the dimLD group showed impaired spatial memory in the Morris Water Maze (MWM) task. The impairment in their MWM performance were reversed when the dimLD group were transferred to the brLD condition for another 4 weeks. The results suggest that lighting conditions influence cognitive function of grass rats in a way similar to that observed in humans, such that bright light is beneficial over dim light for cognitive performance. In addition to the behavioral changes, grass rats in the dimLD condition exhibited reduced expression of brain-derived neurotrophic factor (BDNF) in the hippocampus, most notably in the CA1 subregion. There was also a reduction in dendritic spine density in CA1 apical dendrites in dimLD as compared to the brLD group, and the reduction was mostly in the number of mushroom and stubby spines. When dimLD animals were transferred to the brLD condition for 4 weeks, the hippocampal BDNF and dendritic spine density significantly increased. The results illustrate that not only does light intensity affect cognitive performance, but that it also impacts hippocampal structural plasticity. These studies serve as a starting point to further understand how ambient light modulates neuronal and cognitive functions in diurnal species. A mechanistic understanding of the effects of light on cognition can help to identify risk factors for cognitive decline and contribute to the development of more effective prevention and treatment of cognitive impairment in clinical populations.
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Affiliation(s)
- Joel E Soler
- Department of Psychology, Michigan State University, East Lansing, Michigan
| | - Alfred J Robison
- Department of Physiology, Michigan State University, East Lansing, Michigan
- Neuroscience Program, Michigan State University, East Lansing, Michigan
| | - Antonio A Núñez
- Department of Psychology, Michigan State University, East Lansing, Michigan
- Neuroscience Program, Michigan State University, East Lansing, Michigan
| | - Lily Yan
- Department of Psychology, Michigan State University, East Lansing, Michigan
- Neuroscience Program, Michigan State University, East Lansing, Michigan
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Mendoza-Viveros L, Chiang CK, Ong JLK, Hegazi S, Cheng AH, Bouchard-Cannon P, Fana M, Lowden C, Zhang P, Bothorel B, Michniewicz MG, Magill ST, Holmes MM, Goodman RH, Simonneaux V, Figeys D, Cheng HYM. miR-132/212 Modulates Seasonal Adaptation and Dendritic Morphology of the Central Circadian Clock. Cell Rep 2017; 19:505-520. [PMID: 28423315 PMCID: PMC5864111 DOI: 10.1016/j.celrep.2017.03.057] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Revised: 01/11/2017] [Accepted: 03/17/2017] [Indexed: 02/04/2023] Open
Abstract
The central circadian pacemaker, the suprachiasmatic nucleus (SCN), encodes day length information by mechanisms that are not well understood. Here, we report that genetic ablation of miR-132/212 alters entrainment to different day lengths and non-24 hr day-night cycles, as well as photoperiodic regulation of Period2 expression in the SCN. SCN neurons from miR-132/212-deficient mice have significantly reduced dendritic spine density, along with altered methyl CpG-binding protein (MeCP2) rhythms. In Syrian hamsters, a model seasonal rodent, day length regulates spine density on SCN neurons in a melatonin-independent manner, as well as expression of miR-132, miR-212, and their direct target, MeCP2. Genetic disruption of Mecp2 fully restores the level of dendritic spines of miR-132/212-deficient SCN neurons. Our results reveal that, by regulating the dendritic structure of SCN neurons through a MeCP2-dependent mechanism, miR-132/212 affects the capacity of the SCN to encode seasonal time.
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Affiliation(s)
- Lucia Mendoza-Viveros
- Department of Biology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, ON L5L 1C6, Canada; Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, ON M5S 3G5, Canada
| | - Cheng-Kang Chiang
- Ottawa Institute of Systems Biology, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, 451 Smyth Road, Ottawa, ON K1H 8M5, Canada
| | - Jonathan L K Ong
- Department of Biology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, ON L5L 1C6, Canada
| | - Sara Hegazi
- Department of Biology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, ON L5L 1C6, Canada; Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, ON M5S 3G5, Canada
| | - Arthur H Cheng
- Department of Biology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, ON L5L 1C6, Canada; Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, ON M5S 3G5, Canada
| | - Pascale Bouchard-Cannon
- Department of Biology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, ON L5L 1C6, Canada; Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, ON M5S 3G5, Canada
| | - Michael Fana
- Department of Biology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, ON L5L 1C6, Canada; Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, ON M5S 3G5, Canada
| | - Christopher Lowden
- Department of Biology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, ON L5L 1C6, Canada; Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, ON M5S 3G5, Canada
| | - Peng Zhang
- Department of Biology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, ON L5L 1C6, Canada
| | - Béatrice Bothorel
- Institut des Neurosciences Cellulaires et Intégratives, UPR CNRS 3212, Université de Strasbourg, 5 rue Blaise Pascal, 67084 Strasbourg, France
| | - Matthew G Michniewicz
- Department of Biology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, ON L5L 1C6, Canada
| | - Stephen T Magill
- Vollum Institute, Oregon Health and Science University, Portland, OR 97239, USA
| | - Melissa M Holmes
- Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, ON M5S 3G5, Canada; Department of Psychology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, ON L5L 1C6, Canada
| | - Richard H Goodman
- Vollum Institute, Oregon Health and Science University, Portland, OR 97239, USA
| | - Valérie Simonneaux
- Institut des Neurosciences Cellulaires et Intégratives, UPR CNRS 3212, Université de Strasbourg, 5 rue Blaise Pascal, 67084 Strasbourg, France
| | - Daniel Figeys
- Ottawa Institute of Systems Biology, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, 451 Smyth Road, Ottawa, ON K1H 8M5, Canada; Canadian Institute for Advanced Research, 180 Dundas Street West, Toronto, ON M5G 1Z8, Canada
| | - Hai-Ying M Cheng
- Department of Biology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, ON L5L 1C6, Canada; Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, ON M5S 3G5, Canada.
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Smirnov MS, Evans PR, Garrett TR, Yan L, Yasuda R. Automated Remote Focusing, Drift Correction, and Photostimulation to Evaluate Structural Plasticity in Dendritic Spines. PLoS One 2017; 12:e0170586. [PMID: 28114380 PMCID: PMC5256890 DOI: 10.1371/journal.pone.0170586] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Accepted: 01/08/2017] [Indexed: 01/01/2023] Open
Abstract
Long-term structural plasticity of dendritic spines plays a key role in synaptic plasticity, the cellular basis for learning and memory. The biochemical step is mediated by a complex network of signaling proteins in spines. Two-photon imaging techniques combined with two-photon glutamate uncaging allows researchers to induce and quantify structural plasticity in single dendritic spines. However, this method is laborious and slow, making it unsuitable for high throughput screening of factors necessary for structural plasticity. Here we introduce a MATLAB-based module built for Scanimage to automatically track, image, and stimulate multiple dendritic spines. We implemented an electrically tunable lens in combination with a drift correction algorithm to rapidly and continuously track targeted spines and correct sample movements. With a straightforward user interface to design custom multi-position experiments, we were able to adequately image and produce targeted plasticity in multiple dendritic spines using glutamate uncaging. Our methods are inexpensive, open source, and provides up to a five-fold increase in throughput for quantifying structural plasticity of dendritic spines.
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Affiliation(s)
- Michael S. Smirnov
- Neuronal Signal Transduction, Max Planck Florida Institute for Neuroscience, Jupiter, Florida, United States of America
- * E-mail:
| | - Paul R. Evans
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Tavita R. Garrett
- Neuronal Signal Transduction, Max Planck Florida Institute for Neuroscience, Jupiter, Florida, United States of America
| | - Long Yan
- Light Microscopy Core, Max Planck Florida Institute for Neuroscience, Jupiter, Florida, United States of America
| | - Ryohei Yasuda
- Neuronal Signal Transduction, Max Planck Florida Institute for Neuroscience, Jupiter, Florida, United States of America
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Corniola R, Zou Y, Leu D, Fike JR, Huang TT. Paradoxical relationship between Mn superoxide dismutase deficiency and radiation-induced cognitive defects. PLoS One 2012; 7:e49367. [PMID: 23145165 PMCID: PMC3493523 DOI: 10.1371/journal.pone.0049367] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Accepted: 10/10/2012] [Indexed: 02/04/2023] Open
Abstract
Radiation therapy of the CNS, even at low doses, can lead to deficits in neurocognitive functions. Reduction in hippocampal neurogenesis is usually, but not always, associated with cognitive deficits resulting from radiation therapy. Generation of reactive oxygen species is considered the main cause of radiation-induced tissue injuries, and elevated levels of oxidative stress persist long after the initial cranial irradiation. Consequently, mutant mice with reduced levels of the mitochondrial antioxidant enzyme, Mn superoxide dismutase (MnSOD or Sod2), are expected to be more sensitive to radiation-induced changes in hippocampal neurogenesis and the related functions. In this study, we showed that MnSOD deficiency led to reduced generation of immature neurons in Sod2−/+ mice even though progenitor cell proliferation was not affected. Compared to irradiated Sod2+/+ mice, which showed cognitive defects and reduced differentiation of newborn cells towards the neuronal lineage, irradiated Sod2−/+ mice showed normal hippocampal-dependent cognitive functions and normal differentiation pattern for newborn neurons and astroglia. However, we also observed a disproportional decrease in newborn neurons in irradiated Sod2−/+ following behavioral studies, suggesting that MnSOD deficiency may render newborn neurons more sensitive to stress from behavioral trainings following cranial irradiation. A positive correlation between normal cognitive functions and normal dendritic spine densities in dentate granule cells was observed. The data suggest that maintenance of synaptic connections, via maintenance of dendritic spines, may be important for normal cognitive functions following cranial irradiation.
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Affiliation(s)
- Rikki Corniola
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, California, United States of America
| | - Yani Zou
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, California, United States of America
| | - David Leu
- Palo Alto Institute for Research and Education, Palo Alto, California, United States of America
- Geriatric Research, Education, and Clinical Center (GRECC), VA Palo Alto Health Care System, Palo Alto, California, United States of America
| | - John R. Fike
- Departments of Neurosurgery and Radiation Oncology, University of California San Francisco, San Francisco, California, United States of America
| | - Ting-Ting Huang
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, California, United States of America
- Geriatric Research, Education, and Clinical Center (GRECC), VA Palo Alto Health Care System, Palo Alto, California, United States of America
- * E-mail:
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Chakraborti A, Allen A, Allen B, Rosi S, Fike JR. Cranial irradiation alters dendritic spine density and morphology in the hippocampus. PLoS One 2012; 7:e40844. [PMID: 22815839 PMCID: PMC3397939 DOI: 10.1371/journal.pone.0040844] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2012] [Accepted: 06/14/2012] [Indexed: 01/17/2023] Open
Abstract
Therapeutic irradiation of the brain is a common treatment modality for brain tumors, but can lead to impairment of cognitive function. Dendritic spines are sites of excitatory synaptic transmission and changes in spine structure and number are thought to represent a morphological correlate of altered brain functions associated with hippocampal dependent learning and memory. To gain some insight into the temporal and sub region specific cellular changes in the hippocampus following brain irradiation, we investigated the effects of 10 Gy cranial irradiation on dendritic spines in young adult mice. One week or 1 month post irradiation, changes in spine density and morphology in dentate gyrus (DG) granule and CA1 pyramidal neurons were quantified using Golgi staining. Our results showed that in the DG, there were significant reductions in spine density at both 1 week (11.9%) and 1 month (26.9%) after irradiation. In contrast, in the basal dendrites of CA1 pyramidal neurons, irradiation resulted in a significant reduction (18.7%) in spine density only at 1 week post irradiation. Analysis of spine morphology showed that irradiation led to significant decreases in the proportion of mushroom spines at both time points in the DG as well as CA1 basal dendrites. The proportions of stubby spines were significantly increased in both the areas at 1 month post irradiation. Irradiation did not alter spine density in the CA1 apical dendrites, but there were significant changes in the proportion of thin and mushroom spines at both time points post irradiation. Although the mechanisms involved are not clear, these findings are the first to show that brain irradiation of young adult animals leads to alterations in dendritic spine density and morphology in the hippocampus in a time dependent and region specific manner.
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Affiliation(s)
- Ayanabha Chakraborti
- Department of Neurological Surgery, University of California San Francisco, San Francisco, California, United States of America
- Brain and Spinal Injury Center, University of California San Francisco, San Francisco, California, United States of America
| | - Antino Allen
- Department of Neurological Surgery, University of California San Francisco, San Francisco, California, United States of America
- Brain and Spinal Injury Center, University of California San Francisco, San Francisco, California, United States of America
| | - Barrett Allen
- Department of Neurological Surgery, University of California San Francisco, San Francisco, California, United States of America
- Brain and Spinal Injury Center, University of California San Francisco, San Francisco, California, United States of America
| | - Susanna Rosi
- Department of Neurological Surgery, University of California San Francisco, San Francisco, California, United States of America
- Department of Physical Therapy and Rehabilitation Science, University of California San Francisco, San Francisco, California, United States of America
- Brain and Spinal Injury Center, University of California San Francisco, San Francisco, California, United States of America
| | - John R. Fike
- Department of Neurological Surgery, University of California San Francisco, San Francisco, California, United States of America
- Department of Radiation Oncology, University of California San Francisco, San Francisco, California, United States of America
- Brain and Spinal Injury Center, University of California San Francisco, San Francisco, California, United States of America
- * E-mail:
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Abstract
Layer 2/3 (L2/3) pyramidal neurons are the most abundant cells of the neocortex. Despite their key position in the cortical microcircuit, synaptic integration in dendrites of L2/3 neurons is far less understood than in L5 pyramidal cell dendrites, mainly because of the difficulties in obtaining electrical recordings from thin dendrites. Here we directly measured passive and active properties of the apical dendrites of L2/3 neurons in rat brain slices using dual dendritic-somatic patch-clamp recordings and calcium imaging. Unlike L5 cells, L2/3 dendrites displayed little sag in response to long current pulses, which suggests a low density of I(h) in the dendrites and soma. This was also consistent with a slight increase in input resistance with distance from the soma. Brief current injections into the apical dendrite evoked relatively short (half-width 2-4 ms) dendritic spikes that were isolated from the soma for near-threshold currents at sites beyond the middle of the apical dendrite. Regenerative dendritic potentials and large concomitant calcium transients were also elicited by trains of somatic action potentials (APs) above a critical frequency (130 Hz), which was slightly higher than in L5 neurons. Initiation of dendritic spikes was facilitated by backpropagating somatic APs and could cause an additional AP at the soma. As in L5 neurons, we found that distal dendritic calcium transients are sensitive to a long-lasting block by GABAergic inhibition. We conclude that L2/3 pyramidal neurons can generate dendritic spikes, sharing with L5 pyramidal neurons fundamental properties of dendritic excitability and control by inhibition.
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Affiliation(s)
- Matthew Evan Larkum
- Abteilung Zellphysiologie, Max-Planck-Institut für Medizinische Forschung, D-69120 Heidelberg, Germany.
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Bourne JN, Sorra KE, Hurlburt J, Harris KM. Polyribosomes are increased in spines of CA1 dendrites 2 h after the induction of LTP in mature rat hippocampal slices. Hippocampus 2007; 17:1-4. [PMID: 17094086 DOI: 10.1002/hipo.20238] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [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] [Indexed: 12/26/2022]
Abstract
Enduring long-term potentiation (LTP) requires immediate protein synthesis, hence we assessed whether more polyribosomes are present in dendritic spines of mature hippocampal dendrites after the induction of LTP. Reconstructions from serial section transmission electron microscopy (sSTEM) revealed more dendritic polyribosomes 2 h posttetanus, relative to low-frequency stimulation (LFS). Polyribosomes were present in spines of all shapes with larger postsynaptic densities after 2 h, suggesting a coordinated local protein synthesis among many synapses to replenish proteins utilized during an earlier phase of LTP.
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Affiliation(s)
- Jennifer N Bourne
- Synapses and Cognitive Neuroscience Center, Medical College of Georgia, Augusta, Georgia, USA
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Bourne JN, Kirov SA, Sorra KE, Harris KM. Warmer preparation of hippocampal slices prevents synapse proliferation that might obscure LTP-related structural plasticity. Neuropharmacology 2006; 52:55-9. [PMID: 16895730 DOI: 10.1016/j.neuropharm.2006.06.020] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [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: 05/31/2006] [Revised: 06/23/2006] [Accepted: 06/27/2006] [Indexed: 10/24/2022]
Abstract
The hippocampal slice is a popular model system in which to study the cellular properties of long-term potentiation (LTP). Synaptogenesis induced by exposure to ice-cold artificial cerebrospinal fluid (ACSF), however, raises the concern that morphological correlates of LTP might be obscured, especially in mature slices. Here we demonstrate that preparation of mature hippocampal slices at room temperature (approximately 25 degrees C) maintains excellent ultrastructure and a synapse density comparable to perfusion-fixed hippocampus. These results suggest that slices prepared at room temperature might provide a better basis from which to detect LTP-related changes in synapse number and morphology.
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Affiliation(s)
- Jennifer N Bourne
- Synapses and Cognitive Neuroscience Center, Medical College of Georgia, Augusta, GA 30912-2630, USA
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