801
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Armstrong V, Reichel CM, Doti JF, Crawford CA, McDougall SA. Repeated amphetamine treatment causes a persistent elevation of glial fibrillary acidic protein in the caudate-putamen. Eur J Pharmacol 2004; 488:111-5. [PMID: 15044042 DOI: 10.1016/j.ejphar.2004.02.001] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2003] [Revised: 01/26/2004] [Accepted: 02/03/2004] [Indexed: 12/29/2022]
Abstract
The ability of repeated D-amphetamine (2 mg/kg) treatment to induce behavioral sensitization in rats and alter glial fibrillary acidic protein (GFAP), dopamine transporter (DAT) and glutamate transporter-1 (GLT-1) immunoreactivities was assessed after a 10-day drug abstinence period. Results showed that a sensitizing regimen of amphetamine caused a persistent increase in the number of GFAP-positive cells in the dorsal and ventral caudate-putamen. DAT and GLT-1 immunoreactivities were unaffected. Although the elevated GFAP expression may be due to a mild neurotoxicity, it is also possible that amphetamine-induced increases in GFAP reflect adaptive changes that may be associated with processes underlying behavioral sensitization.
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Affiliation(s)
- Victoria Armstrong
- Department of Psychology, California State University, San Bernardino, CA 92407, USA
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802
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Burbach GJ, Dehn D, Nagel B, Del Turco D, Deller T. Laser microdissection of immunolabeled astrocytes allows quantification of astrocytic gene expression. J Neurosci Methods 2004; 138:141-8. [PMID: 15325122 DOI: 10.1016/j.jneumeth.2004.03.022] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2004] [Revised: 03/29/2004] [Accepted: 03/30/2004] [Indexed: 10/26/2022]
Abstract
Astrocytes represent the major glial cell population within the central nervous system. In order to elucidate the function of astrocytes under physiological conditions and during the course of neurological disease, astrocytic gene expression profiling is necessary. However, since astrocytes form an intimately connected network with neurons and other cell types in the brain, gene expression analysis of astrocytes with a sufficient degree of cellular specificity is difficult. Here we are presenting a rapid and, thus, RNA preserving immunostaining protocol for the detection of astrocytes in rodent brain. This protocol can readily be combined with laser microdissection (Leica AS LMD platform) and quantitative RT-PCR (qPCR). Employing this method, we studied changes in glial fibrillary acidic protein (GFAP) expression in astrocytes of mouse entorhinal cortex following entorhinal cortex lesion. Using laser microdissection, astrocytes (n = 60) were collected in the tissue surrounding the lesion, the entorhinal cortex contralateral to the lesion, and in unlesioned control animals. Changes in GFAP mRNA were quantified using qPCR. GFAP mRNA levels were 82-fold higher in astrocytes of lesioned animals at the site of the lesion compared to GFAP mRNA levels in entorhinal cortex astrocytes of control mice. GFAP mRNA levels were only slightly elevated at the contralateral side (lesioned animals). This optimized protocol for immunolabeling and laser microdissection of astrocytes followed by qPCR allows quantification of astrocytic gene expression levels with a high degree of cellular specificity. It may similarly be employed in different settings where other cell types need to be identified and microdissected for gene expression profiling.
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Affiliation(s)
- Guido J Burbach
- Institute of Clinical Neuroanatomy, Johann Wolfgang Goethe-University, Theodor-Stern-Kai 7, D-60590 Frankfurt am Main, Germany
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803
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Wood H. Astrocytes grab a piece of the action. Nat Rev Neurosci 2004. [DOI: 10.1038/nrn1542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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804
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Ashour F, Deuchars J. Electron microscopic localisation of P2X4 receptor subunit immunoreactivity to pre- and post-synaptic neuronal elements and glial processes in the dorsal vagal complex of the rat. Brain Res 2004; 1026:44-55. [PMID: 15476696 DOI: 10.1016/j.brainres.2004.08.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/10/2004] [Indexed: 12/23/2022]
Abstract
P2X receptors are ligand gated ion channels activated by extracellular ATP. There are seven P2X subunits, P2X(1-7), and all are expressed in the CNS. The P2X(4) receptor subunit (P2X(4)R) is likely to be important in the CNS as it has been reported to be expressed throughout the brain and spinal cord. However, P2X(4)Rs have been identified as restricted to neurones, only in glia or expressed in both neurones and glia with no discernible relationship to CNS region or epitope target of antibodies used for staining. In addition, although there are particularly high levels of mRNA encoding P2X(4)R in the brainstem, previous immunohistochemical studies have revealed only indistinct staining. We therefore examined the distribution of P2X(4)R in the dorsal vagal complex (DVC) of the brainstem using immunohistochemistry in sections obtained from adult Wistar rats transcardially perfused with aldehyde fixatives. When this revealed staining identifiable only as small puncta at the light microscope level, we examined the area with electron microscopy. This ultrastructural study revealed that P2X(4)R immunoreactivity (IR) was present in neurones at both pre- and post-synaptic sites as well as in glial cell processes and somata. This P2X(4)R-IR was localised adjacent to plasma membranes, as well as internally in membrane bound structures resembling endosomes. Immunoreactivity in endosomes was more prominent following antigen retrieval protocols. Localisation of P2X(4)R-IR in astrocytes, identified by the presence of glial fibrillary acidic protein (GFAP), was confirmed using immunofluorescence. The presence of P2X(4)Rs in the dorsal vagal complex is consistent with expression studies, but some reasons for a lack of correlation with pharmacological studies are discussed. The P2X(4)R is therefore expressed by neurones and glia in the dorsal vagal complex and may play a role in mediating extracellular signalling by ATP in this region.
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Affiliation(s)
- Fathia Ashour
- School of Biomedical Sciences, University of Leeds, Leeds, LS2 9NQ, UK
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805
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Ostrow LW, Sachs F. Mechanosensation and endothelin in astrocytes--hypothetical roles in CNS pathophysiology. ACTA ACUST UNITED AC 2004; 48:488-508. [PMID: 15914254 DOI: 10.1016/j.brainresrev.2004.09.005] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2003] [Revised: 08/19/2004] [Accepted: 09/09/2004] [Indexed: 01/23/2023]
Abstract
Endothelin (ET) is a potent autocrine mitogen produced by reactive and neoplastic astrocytes. ET has been implicated in the induction of astrocyte proliferation and other transformations engendered by brain pathology, and in promoting the malignant behavior of astrocytomas. Reactive astrocytes containing ET are found in the periphery/penumbra of a wide array of CNS pathologies. Virtually all brain pathology deforms the surrounding parenchyma, either by direct mass effect or edema. Mechanical stress is a well established stimulus for ET production and release by other cell types, but has not been well studied in the brain. However, numerous studies have illustrated that astrocytes can sense mechanical stress and translate it into chemical messages. Furthermore, the ubiquitous reticular meshwork formed by interconnected astrocytes provides an ideal morphology for sensing and responding to mechanical disturbances. We have recently demonstrated stretch-induced ET production by astrocytes in vitro. Inspired by this finding, the purpose of this article is to review the literature on (1) astrocyte mechanosensation, and (2) the endothelin system in astrocytes, and to consider the hypothesis that mechanical induction of the ET system may influence astrocyte functioning in CNS pathophysiology. We conclude by discussing evidence supporting future investigations to determine whether specific inhibition of stretch-activated ion channels may represent a novel strategy for treating or preventing CNS disturbances, as well as the relevance to astrocyte-derived tumors.
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Affiliation(s)
- Lyle W Ostrow
- Department of Physiology and Biophysics, S.U.N.Y. at Buffalo, School of Medicine and Biomedical Sciences, Buffalo, NY 14214, USA
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806
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Fellin T, Pascual O, Gobbo S, Pozzan T, Haydon PG, Carmignoto G. Neuronal synchrony mediated by astrocytic glutamate through activation of extrasynaptic NMDA receptors. Neuron 2004; 43:729-43. [PMID: 15339653 DOI: 10.1016/j.neuron.2004.08.011] [Citation(s) in RCA: 713] [Impact Index Per Article: 35.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2004] [Revised: 07/26/2004] [Accepted: 08/06/2004] [Indexed: 11/17/2022]
Abstract
Fast excitatory neurotransmission is mediated by activation of synaptic ionotropic glutamate receptors. In hippocampal slices, we report that stimulation of Schaffer collaterals evokes in CA1 neurons delayed inward currents with slow kinetics, in addition to fast excitatory postsynaptic currents. Similar slow events also occur spontaneously, can still be observed when neuronal activity and synaptic glutamate release are blocked, and are found to be mediated by glutamate released from astrocytes acting preferentially on extrasynaptic NMDA receptors. The slow currents can be triggered by stimuli that evoke Ca2+ oscillations in astrocytes, including photolysis of caged Ca2+ in single astrocytes. As revealed by paired recording and Ca2+ imaging, a striking feature of this NMDA receptor response is that it occurs synchronously in multiple CA1 neurons. Our results reveal a distinct mechanism for neuronal excitation and synchrony and highlight a functional link between astrocytic glutamate and extrasynaptic NMDA receptors.
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Affiliation(s)
- Tommaso Fellin
- Istituto CNR di Neuroscienze, Università di Padova, viale G. Colombo 3, 35121, Italy
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807
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Abstract
Nearly one-half of the cells in a human brain are astrocytes, but the function of these little cells remains a great mystery. Astrocytes form an intimate association with synapses throughout the adult CNS, where they help regulate ion and neurotransmitter concentrations. Recent in vitro studies, however, have found that astrocytes also exert powerful control over the number of CNS synapses that form, are essential for postsynaptic function, and are required for synaptic stability and maintenance. Moreover, recent studies increasingly implicate astrocytes in vivo as participants in activity-dependent structural and functional synaptic changes throughout the nervous system. Taken together, these data force us to rethink the role of glia. We propose that astrocytes should not be viewed primarily as support cells, but rather as cells that actively control the structural and functional plasticity of synapses in developing and adult organisms.
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Affiliation(s)
- Erik M Ullian
- Department of Neurobiology, Stanford University School of Medicine, Stanford, California
| | - Karen S Christopherson
- Department of Neurobiology, Stanford University School of Medicine, Stanford, California
| | - Ben A Barres
- Department of Neurobiology, Stanford University School of Medicine, Stanford, California
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808
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Nimmerjahn A, Kirchhoff F, Kerr JND, Helmchen F. Sulforhodamine 101 as a specific marker of astroglia in the neocortex in vivo. Nat Methods 2004; 1:31-7. [PMID: 15782150 DOI: 10.1038/nmeth706] [Citation(s) in RCA: 614] [Impact Index Per Article: 30.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2004] [Accepted: 08/26/2004] [Indexed: 11/08/2022]
Abstract
Glial cells have been identified as key signaling components in the brain; however, methods to investigate their structure and function in vivo have been lacking. Here, we describe a new, highly selective approach for labeling astrocytes in intact rodent neocortex that allows in vivo imaging using two-photon microscopy. The red fluorescent dye sulforhodamine 101 (SR101) was specifically taken up by protoplasmic astrocytes after brief exposure to the brain surface. Specificity was confirmed by immunohistochemistry. In addition, SR101 labeled enhanced green fluorescent protein (EGFP)-expressing astrocytes but not microglial cells in transgenic mice. We used SR101 labeling to quantify morphological characteristics of astrocytes and to visualize their close association with the cortical microvasculature. Furthermore, by combining this method with calcium indicator loading of cell populations, we demonstrated distinct calcium dynamics in astroglial and neuronal networks. We expect SR101 staining to become a principal tool for investigating astroglia in vivo.
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Affiliation(s)
- Axel Nimmerjahn
- Abteilung Zellphysiologie, Max-Planck Institut für medizinische Forschung, Jahnstr. 29, 69120 Heidelberg, Germany
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809
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López-Toledano MA, Shelanski ML. Neurogenic effect of beta-amyloid peptide in the development of neural stem cells. J Neurosci 2004; 24:5439-44. [PMID: 15190117 PMCID: PMC6729298 DOI: 10.1523/jneurosci.0974-04.2004] [Citation(s) in RCA: 172] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The adult mammalian brain contains neural stem cells (NSCs) with self-renewal and multilineage potential in the hippocampus and subventricular zone. However, neurogenesis from these areas does not compensate for neuronal loss in age-related neurodegenerative disorders such as Alzheimer's disease (AD). To test whether an impairment of neurogenesis could contribute to the pathogenesis of AD, we examined the effects of amyloid-beta peptide (Abeta) on the survival and neuronal differentiation of cultured NSCs from striatum and hippocampus. We show that Abeta peptide does not impair the neurogenic rate in NSC progeny, but that it increases the total number of neurons in vitro in a dose-dependent manner. The neurogenic effect of Abeta peptide is not dependent on soluble factors released from the NSC progeny. Neurogenesis is induced by Abeta42 and not Abeta40 or Abeta 25-35, and the activity appears to be a property of Abeta oligomers and not fibrils. These results suggest that Abeta may have positive as well as deleterious actions, and that a knowledge of the mechanisms involved in the former could be valuable in exploiting the regenerative and plastic potential of the brain in preventing and treating Alzheimer's disease.
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Affiliation(s)
- Miguel A López-Toledano
- Taub Institute for Research on Alzheimer's Disease and the Aging Brain and Department of Pathology, Columbia University, New York, New York 10032, USA
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810
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ATP regulates anion channel-mediated organic osmolyte release from cultured rat astrocytes via multiple Ca2+-sensitive mechanisms. Am J Physiol Cell Physiol 2004; 288:C204-13. [PMID: 15371260 DOI: 10.1152/ajpcell.00330.2004] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ubiquitously expressed volume-regulated anion channels (VRACs) are activated in response to cell swelling but may also show limited activity in nonswollen cells. VRACs are permeable to inorganic anions and small organic osmolytes, including the amino acids aspartate, glutamate, and taurine. Several recent reports have demonstrated that neurotransmitters or hormones, such as ATP and vasopressin, induce or strongly potentiate astrocytic whole cell Cl(-) currents and amino acid release, which are inhibited by VRAC blockers. In the present study, we explored the intracellular signaling mechanisms mediating the effects of ATP on d-[(3)H]aspartate release via the putative VRAC pathway in rat primary astrocyte cultures. Cells were exposed to moderate (5%) or substantial (30%) reductions in medium osmolarity. ATP strongly potentiated d-[(3)H]aspartate release in both moderately swollen and substantially swollen cells. These ATP effects were blocked (>or=80% inhibition) by intracellular Ca(2+) chelation with BAPTA-AM, calmodulin inhibitors, or a combination of the inhibitors of protein kinase C (PKC) and calmodulin-dependent kinase II (CaMK II). In contrast, control d-[(3)H]aspartate release activated by the substantial hyposmotic swelling showed little (<or=25% inhibition) sensitivity to the same pharmacological agents. These data indicate that ATP regulates VRAC activity via two separate Ca(2+)-sensitive signaling cascades involving PKC and CaMK II and that cell swelling per se activates VRACs via a separate Ca(2+)/calmodulin-independent signaling mechanism. Ca(2+)-dependent organic osmolyte release via VRACs may contribute to the physiological functions of these channels in the brain, including astrocyte-to-neuron intercellular communication.
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811
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Spataro LE, Sloane EM, Milligan ED, Wieseler-Frank J, Schoeniger D, Jekich BM, Barrientos RM, Maier SF, Watkins LR. Spinal gap junctions: Potential involvement in pain facilitation. THE JOURNAL OF PAIN 2004; 5:392-405. [PMID: 15501197 DOI: 10.1016/j.jpain.2004.06.006] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2004] [Revised: 06/23/2004] [Accepted: 06/29/2004] [Indexed: 11/17/2022]
Abstract
UNLABELLED Glia are now recognized as important contributors in pathological pain creation and maintenance. Spinal cord glia exhibit extensive gap junctional connectivity, raising the possibility that glia are involved in the contralateral spread of excitation resulting in mirror image pain. In the present experiments, the gap junction decoupler carbenoxolone was administered intrathecally after induction of neuropathic pain in response to sciatic nerve inflammation (sciatic inflammatory neuropathy) or partial nerve injury (chronic constriction injury). In both neuropathic pain models, a low dose of carbenoxolone reversed mirror image mechanical allodynia, while leaving ipsilateral mechanical allodynia unaffected. Ipsilateral thermal hyperalgesia was briefly attenuated. Critically, blockade of mechanical allodynia and thermal hyperalgesia was not observed in response to intrathecal glycyrrhizic acid, a compound similar to carbenoxolone in all respects but it does not decouple gap junctions. Thus, blockade of mechanical allodynia and thermal hyperalgesia by carbenoxolone does appear to reflect an effect on gap junctions. Examination of carbenoxolone's effects on intrathecal human immunodeficiency virus type 1 gp120 showed that blockade of pain facilitation might result, at least in part, via suppression of interleukin-1 and, in turn, interleukin-6. These data provide the first suggestion that spread of excitation via gap junctions might contribute importantly to inflammatory and traumatic neuropathic pain. PERSPECTIVE The current studies provide evidence for involvement of gap junctions in spinal cord pain facilitation. Intrathecal carbenoxolone, a gap junction decoupler, reversed neuropathy-induced mirror image pain and intrathecal gp120-induced allodynia. In addition, it decreased gp120-induced proinflammatory cytokines. This suggests gap junction activation might lead to proinflammatory cytokine release by distantly activated glia.
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Affiliation(s)
- Leah E Spataro
- Department of Psychology & The Center for Neuroscience, University of Colorado at Boulder, Boulder, Colorado 90309-0345, USA
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812
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Weissman TA, Riquelme PA, Ivic L, Flint AC, Kriegstein AR. Calcium Waves Propagate through Radial Glial Cells and Modulate Proliferation in the Developing Neocortex. Neuron 2004; 43:647-61. [PMID: 15339647 DOI: 10.1016/j.neuron.2004.08.015] [Citation(s) in RCA: 408] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2002] [Revised: 04/12/2004] [Accepted: 08/05/2004] [Indexed: 12/31/2022]
Abstract
The majority of neurons in the adult neocortex are produced embryonically during a brief but intense period of neuronal proliferation. The radial glial cell, a transient embryonic cell type known for its crucial role in neuronal migration, has recently been shown to function as a neuronal progenitor cell and appears to produce most cortical pyramidal neurons. Radial glial cell modulation could thus affect neuron production, neuronal migration, and overall cortical architecture; however, signaling mechanisms among radial glia have not been studied directly. We demonstrate here that calcium waves propagate through radial glial cells in the proliferative cortical ventricular zone (VZ). Radial glial calcium waves occur spontaneously and require connexin hemichannels, P2Y1 ATP receptors, and intracellular IP3-mediated calcium release. Furthermore, we show that wave disruption decreases VZ proliferation during the peak of embryonic neurogenesis. Taken together, these results demonstrate a radial glial signaling mechanism that may regulate cortical neuronal production.
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Affiliation(s)
- Tamily A Weissman
- Center for Neurobiology and Behavior, Columbia University, New York, NY 10032, USA
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813
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Kimelberg HK. Increased release of excitatory amino acids by the actions of ATP and peroxynitrite on volume-regulated anion channels (VRACs) in astrocytes. Neurochem Int 2004; 45:511-9. [PMID: 15186917 DOI: 10.1016/j.neuint.2003.11.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/10/2003] [Indexed: 01/01/2023]
Abstract
Rapid swelling of astrocytes in primary culture by exposure to hyposmotic medium (or slower swelling by exposure to high K+ medium) leads to release of the excitatory amino acids (EAAs) glutamate and aspartate. One question that arises is whether these phenomena are only relevant to pathological states such as ischemia and trauma where marked astrocytic swelling occurs or whether much smaller astrocytic volume changes, that might be encountered under physiological states, will cause such release. We have recently found that extracellular ATP strongly potentiated volume-regulated anion channels (VRACs)-mediated-excitatory amino acid release in non-swollen and osmotically swollen primary astrocyte cultures. However, ATP does not seem to directly activate but instead positively modulates VRACs and we postulate that a minor fraction of these are active under isoosmotic conditions based on the finding that in hyperosmotic media the ATP-induced increase was inhibited. Agonist and inhibitor analysis suggests that the effect of ATP is mediated by several subtypes of metabotropic P2Y receptors. Thus, the concept of volume transmission may be extended to volume-mediated transmission, whereby moderate cell swelling causes release of neurotransmitter substances. The product of the superoxide oxygen radical and nitric oxide, peroxynitrite, formed under pathological conditions such as cerebral ischemia, also potentiated the release of D-[3H]aspartate from astrocyte cultures exposed to limited or marked swelling via intracellular signaling mechanisms involving tyrosine kinases (TKs). Thus, the enhancement of cell volume-dependent release of excitatory amino acids from astrocytes can be physiological or pathological and its magnitude depends on the degree of the cell volume increase.
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Affiliation(s)
- Harold K Kimelberg
- Neural and Vascular Biology Theme, Ordway Research Institute, Inc., 150 New Scotland Ave., Albany, NY 12208, USA.
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814
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Même W, Ezan P, Venance L, Glowinski J, Giaume C. ATP-induced inhibition of gap junctional communication is enhanced by interleukin-1 beta treatment in cultured astrocytes. Neuroscience 2004; 126:95-104. [PMID: 15145076 DOI: 10.1016/j.neuroscience.2004.03.031] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/23/2004] [Indexed: 11/23/2022]
Abstract
Nucleotides are signaling molecules involved in variety of interactions between neurons, between glial cells as well as between neurons and glial cells. In addition, ATP and other nucleotides are massively released following brain insults, including inflammation, and may thereby be involved in mechanisms of cerebral injury. Recent concepts have shown that in astrocytes intercellular communication through gap junctions may play an important role in neuroprotection. Therefore, we have studied the effects of nucleotides on gap junction communication in astrocytes. Based on measurement of intercellular dye coupling and recording of junctional currents, the present study shows that ATP (10-100 microM) induces a rapid and a concentration-dependent inhibition of gap junction communication in cultured cortical astrocytes from newborn mice. Effects of agonists and antagonists of purinergic receptors indicate that the inhibition of gap junctional communication by ATP mainly involves the stimulation of metabotropic purinergic 1 (P2Y(1)) receptors. Pretreatment with the pro-inflammatory cytokine interleukin-1beta (10 ng/ml, 24 h), which has no effect by itself on gap junctional communication, increases the inhibitory effect of ATP and astrocytes become sensitive to uridine 5'-triphosphate (UTP). As indicated by the enhanced expression of P2Y(2) receptor mRNA, P2Y(2) receptors are responsible for the increased responses evoked by ATP and UTP in interleukin-1beta-treated cells. In addition, the effect of endothelin-1, a well-known inhibitor of gap junctional communication in astrocytes was also exacerbated following interleukin-1beta treatment. We conclude that ATP decreases intercellular communication through gap junctions in astrocytes and that the increased sensitivity of gap junction channels to nucleotides and endothelin-1 is a characteristic feature of astrocytes exposed to pro-inflammatory treatments.
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Affiliation(s)
- W Même
- INSERM U114, Collège de France, 11 Place Marcelin Berthelot, 75231 Paris, Cedex 05, France
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815
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Dienel GA, Cruz NF. Nutrition during brain activation: does cell-to-cell lactate shuttling contribute significantly to sweet and sour food for thought? Neurochem Int 2004; 45:321-51. [PMID: 15145548 DOI: 10.1016/j.neuint.2003.10.011] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2003] [Revised: 10/24/2003] [Accepted: 10/27/2003] [Indexed: 10/26/2022]
Abstract
Functional activation of astrocytic metabolism is believed, according to one hypothesis, to be closely linked to excitatory neurotransmission and to provide lactate as fuel for oxidative metabolism in neighboring neurons. However, review of emerging evidence suggests that the energetic demands of activated astrocytes are higher and more complex than recognized and much of the lactate presumably produced by astrocytes is not locally oxidized during activation. In vivo activation studies in normal subjects reveal that the rise in consumption of blood-borne glucose usually exceeds that of oxygen, especially in retina compared to brain. When the contribution of glycogen, the brain's major energy reserve located in astrocytes, is taken into account the magnitude of the carbohydrate-oxygen utilization mismatch increases further because the magnitude of glycogenolysis greatly exceeds the incremental increase in utilization of blood-borne glucose. Failure of local oxygen consumption to equal that of glucose plus glycogen in vivo is strong evidence against stoichiometric transfer of lactate from astrocytes to neighboring neurons for oxidation. Thus, astrocytes, not nearby neurons, use the glycogen for energy during physiological activation in normal brain. These findings plus apparent compartmentation of metabolism of glycogen and blood-borne glucose during activation lead to our working hypothesis that activated astrocytes have high energy demands in their fine perisynaptic processes (filopodia) that might be met by glycogenolysis and glycolysis coupled to rapid lactate clearance. Tissue culture studies do not consistently support the lactate shuttle hypothesis because key elements of the model, glutamate-induced increases in glucose utilization and lactate release, are not observed in many astrocyte preparations, suggesting differences in their oxidative capacities that have not been included in the model. In vivo nutritional interactions between working neurons and astrocytes are not as simple as implied by "sweet (glucose-glycogen) and sour (lactate) food for thought."
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Affiliation(s)
- Gerald A Dienel
- Department of Neurology, Slot 830, University of Arkansas for Medical Sciences, Room 715, Shorey Building, 4301 W. Markham Street, Little Rock, AR 72205, USA.
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816
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Rouach N, Koulakoff A, Giaume C. Neurons set the tone of gap junctional communication in astrocytic networks. Neurochem Int 2004; 45:265-72. [PMID: 15145542 DOI: 10.1016/j.neuint.2003.07.004] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2003] [Accepted: 07/31/2003] [Indexed: 11/20/2022]
Abstract
A number of studies have contributed to demonstrate that neurons and astrocytes tightly and actively interact. Indeed, the presence of astrocytes in neuronal cultures increases the number of synapses and their efficiency, and thanks to enzymatic and uptake processes, astrocytes play a role in neuroprotection. A typical feature of astrocytes is that they establish cell-cell communication in vitro, as well as in situ, through intercellular channels forming specialized membrane areas defined as gap junctions. These channels are composed of junctional proteins termed connexins (Cxs): in astrocytes connexin 43 (Cx43) and 30 (Cx30) have been shown to prevail. Several recent works indicate that gap junctional communication (GJC) and/or connexin expression in astrocytes are controlled by neurons. Altogether, these observations lead to the concept that neuronal and astrocytic networks interact through mutual setting of their respective mode of communication and that astrocyte gap junctions represent a target in neuroglial interaction.
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Affiliation(s)
- Nathalie Rouach
- INSERM U114, Collège de France, 11 Place Marcelin Berthelot, 75005 Paris, France
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817
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Kielian T, Esen N. Effects of neuroinflammation on glia-glia gap junctional intercellular communication: a perspective. Neurochem Int 2004; 45:429-36. [PMID: 15145557 DOI: 10.1016/j.neuint.2003.09.010] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2003] [Revised: 09/15/2003] [Accepted: 09/15/2003] [Indexed: 11/23/2022]
Abstract
Gap junctions serve as intercellular conduits that allow for the direct transfer of small molecular weight molecules (up to 1 kDa) including ions involved in cellular excitability, metabolic precursors, and second messengers. The observation of extensive intercellular coupling and large numbers of gap junctions in the central nervous system (CNS) suggests a syncytium-like organization of glial compartments. Inflammation is a hallmark of various CNS diseases such as bacterial and viral infections, multiple sclerosis, Alzheimer's disease, and cerebral ischemia. A general consequence of brain inflammation is reactive gliosis typified by astrocyte hypertrophy and proliferation of astrocytes and microglia. Changes in gap junction intercellular communication as reflected by alterations in dye coupling and connexin expression have been associated with numerous CNS inflammatory diseases, which may have dramatic implications on the survival of neuronal and glial populations in the context of neuroinflammation. A review of the effects of inflammatory products on glia-glia gap junctional communication and glial glutamate release is presented. In addition, the hypothesis of a "syncytial switch" based upon differential regulation of gap junction expression in astrocytes and microglia during normal CNS homeostasis and neuroinflammation is proposed.
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Affiliation(s)
- Tammy Kielian
- Department of Neurobiology and Developmental Sciences, University of Arkansas for Medical Sciences, 4301 W. Markham Street, Slot 510, Little Rock, AR 72205, USA.
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818
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Abstract
Originally ascribed to having only passive roles in the CNS, astrocytes are now known to have an active role in the regulation of synaptic transmission. Neuronal activity can evoke Ca(2+) transients in astrocytes and Ca(2+) transients in astrocytes can evoke changes in neuronal activity. The excitatory neurotransmitter glutamate has been shown to mediate such bi-directional communication between astrocytes and neurons. We demonstrate here that ATP, a primary mediator of intercellular Ca(2+) signaling among astrocytes, also mediates intercellular signaling between astrocytes and neurons in hippocampal cultures. Mechanical stimulation of astrocytes evoked Ca(2+) waves mediated by the release of ATP and activation of P2 receptors. Mechanically evoked Ca(2+) waves led to decreased excitatory glutamatergic synaptic transmission in an ATP-dependent manner. Exogenous application of ATP does not affect post-synaptic glutamatergic responses but decreased pre-synaptic exocytotic events. Finally, we show that astrocytes exhibit spontaneous Ca(2+) oscillations mediated by extracellular ATP and that inhibition of these Ca(2+) responses enhanced excitatory glutamatergic transmission. We therefore conclude that ATP released from astrocytes exerts tonic and activity-dependent down-regulation of synaptic transmission via pre-synaptic mechanisms.
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Affiliation(s)
- Schuichi Koizumi
- Division of Pharmacology, National Institute of Health Sciences.
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819
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Wang X, Arcuino G, Takano T, Lin J, Peng WG, Wan P, Li P, Xu Q, Liu QS, Goldman SA, Nedergaard M. P2X7 receptor inhibition improves recovery after spinal cord injury. Nat Med 2004; 10:821-7. [PMID: 15258577 DOI: 10.1038/nm1082] [Citation(s) in RCA: 397] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2004] [Accepted: 06/25/2004] [Indexed: 01/29/2023]
Abstract
Secondary injury exacerbates the extent of spinal cord insults, yet the mechanistic basis of this phenomenon has largely been unexplored. Here we report that broad regions of the peritraumatic zone are characterized by a sustained process of pathologic, high ATP release. Spinal cord neurons expressed P2X7 purine receptors (P2X7R), and exposure to ATP led to high-frequency spiking, irreversible increases in cytosolic calcium and cell death. To assess the potential effect of P2X7R blockade in ameliorating acute spinal cord injury (SCI), we delivered P2X7R antagonists OxATP or PPADS to rats after acute impact injury. We found that both OxATP and PPADS significantly improved functional recovery and diminished cell death in the peritraumatic zone. These observations demonstrate that SCI is associated with prolonged purinergic receptor activation, which results in excitotoxicity-based neuronal degeneration. P2X7R antagonists inhibit this process, reducing both the histological extent and functional sequelae of acute SCI.
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Affiliation(s)
- Xiaohai Wang
- Department of Neurosurgery, Center for Aging and Developmental Biology, University of Rochester Medical Center, Rochester, New York 14642, USA
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820
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Abstract
For many years, astrocytes and oligodendrocytes were considered the inert partners of neurons in the central nervous system (CNS), but several recent studies have dramatically challenged this view. Glial cells express a large number of different voltage- and ligand-gated ion channels (Verkhratsky and Steinhäuser. Brain Res Rev 32:380-412, 2000) as well as G-protein-coupled receptors (Verkhratsky et al. Physiol Rev 78:99-141, 1998)-machinery necessary to sense and respond to neuronal activity. These findings raised the fundamental question as to whether glial receptors are stimulated under physiological conditions, and what sorts of events are triggered by such activation. During the early 1990s, P. Haydon and colleagues made the seminal observation that [Ca(2+)](i) rises in cultured astrocytes are associated with the release of glutamate, which suggested that astrocytes respond to activation and play active modulatory roles in intercellular communication (Parpura et al. Nature 369:744-747, 1994). Subsequent studies performed in situ confirmed and extended this initial observation. In this review, we will focus specifically on the hippocampus and sum up evidence of bidirectional communication between astrocytes and neurons emerging from recent studies using acute slice preparations.
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Affiliation(s)
- Andrea Volterra
- Department of Cell Biology and Morphology, University of Lausanne, Lausanne, Switzerland
- Department of Pharmacological Sciences, Center of Excellence on Neurodegenerative Diseases, University of Milan, Milan, Italy
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821
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Gittins R, Harrison PJ. A quantitative morphometric study of the human anterior cingulate cortex. Brain Res 2004; 1013:212-22. [PMID: 15193531 DOI: 10.1016/j.brainres.2004.03.064] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/31/2004] [Indexed: 12/30/2022]
Abstract
Morphometric alterations in the anterior cingulate cortex (ACC) have been reported in schizophrenia and mood disorders. Parameters affected include glial and neuronal density, neuronal size and cortical thickness. Some data, especially in mood disorders, suggest that the left subgenual ACC is preferentially involved. Qualitative studies show that the ACC cytoarchitecture is heterogeneous, but there are few quantitative data. We performed a quantitative morphometric study of five anatomical levels within the ACC (caudal and rostral subgenual [area 24b sg], rostral and intermediate supragenual [area 24b] and caudal supragenual [area 24b']) in both hemispheres of five normal brains. We measured cortical depth, layer depths, neuronal density, neuronal size, and glial density, using the optical disector and nucleator. Relative to the subgenual ACC, the supragenual ACC was thicker, with a deeper layer V. Supragenual neurons were substantially larger in all layers, and were less densely packed in layers V and VI, than subgenual neurons. Glial density, and the glia to neuron ratio, was higher in supragenual than subgenual ACC. Only minor differences were seen between left and right ACC, between caudal and rostral subgenual ACC, and between the three supragenual levels. These data complement the qualitative descriptions of the heterogeneity of human ACC cytoarchitecture, connections, and functions, especially between supragenual and subgenual regions. Our findings also indicate that care must be taken when selecting ACC tissue to be used for morphometric studies of psychiatric disorders, since the normal anatomical variation is of a similar magnitude as the reported disease-related alterations.
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Affiliation(s)
- Rebecca Gittins
- Department of Psychiatry, University of Oxford, Neurosciences Building, Warneford Hospital, OX3 7JX, Oxford, UK
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822
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Wood H. A new release from astrocytes. Nat Rev Neurosci 2004. [DOI: 10.1038/nrn1439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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823
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Mori T, Tateishi N, Kagamiishi Y, Shimoda T, Satoh S, Ono S, Katsube N, Asano T. Attenuation of a delayed increase in the extracellular glutamate level in the peri-infarct area following focal cerebral ischemia by a novel agent ONO-2506. Neurochem Int 2004; 45:381-7. [PMID: 15145552 DOI: 10.1016/j.neuint.2003.06.001] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2003] [Revised: 06/13/2003] [Accepted: 06/14/2003] [Indexed: 11/20/2022]
Abstract
A novel agent, ONO-2506 [(R)-(-)-2-propyloctanoic acid, ONO Pharmaceutical Co. Ltd.] was previously shown to mitigate delayed infarct expansion through inhibition of the enhanced production of S-100beta, while inducing a prompt symptomatic improvement that attained a significant level as early as 24h after drug administration. To elucidate the mechanism underlying the prompt symptomatic improvement, the present study aimed to examine whether ONO-2506 modulates the level of extracellular glutamate ([Glu]e) in the rat subjected to transient middle cerebral artery occlusion (tMCAO). In this model, it had been shown that ONO-2506 reduces the infarct volume, improves the neurological deficits, and enhances the mRNA expression of glial glutamate transporters (GLT-1 and GLAST). The [Glu]e levels in the ischemic cortices were continuously measured using intracerebral microdialysis. The alterations in the [Glu]e levels in the sham-operated and tMCAO-operated groups with or without drug administration were compared. In the tMCAO groups, the [Glu]e level increased during tMCAO to a similar extent, returned to normal on reperfusion, and increased again around 5h. In the saline-treated group, however, the [Glu]e level further increased from 15 h on to reach about 280% of the normal level at 24h. This secondary increase in the [Glu]e level in the late phase of reperfusion was prevented by ONO-2506. The intracerebral infusion of glutamate transporter inhibitor, l-trans-pyrrolidine-2,4-dicarboxylic acid, at 24h after tMCAO induced an increase in the [Glu]e level, which was marked in both the sham-operated and ONO-2506-treated groups, but much less pronounced in the saline-treated group. The above results suggest that functional modulation of activated astrocytes by pharmacological agents like ONO-2506 may inhibit the secondary rise of [Glu]e level in the late phase of reperfusion, leading to amelioration of delayed infarct expansion and neurological deficits.
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Affiliation(s)
- Takashi Mori
- Institute of Laboratory Animal Science, Saitama Medical Center/School, 1981 Kamoda, Kawagoe, Saitama 350-8550, Japan.
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824
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Sanjana NE, Fuller SB. A fast flexible ink-jet printing method for patterning dissociated neurons in culture. J Neurosci Methods 2004; 136:151-63. [PMID: 15183267 DOI: 10.1016/j.jneumeth.2004.01.011] [Citation(s) in RCA: 178] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2003] [Revised: 01/09/2004] [Accepted: 01/09/2004] [Indexed: 11/21/2022]
Abstract
We present a new technique that uses a custom-built ink-jet printer to fabricate precise micropatterns of cell adhesion materials for neural cell culture. Other work in neural cell patterning has employed photolithography or "soft lithographic" techniques such as micro-stamping, but such approaches are limited by their use of an un-alterable master pattern such as a mask or stamp master and can be resource-intensive. In contrast, ink-jet printing, used in low-cost desktop printers, patterns material by depositing microscopic droplets under robotic control in a programmable and inexpensive manner. We report the use of ink-jet printing to fabricate neuron-adhesive patterns such as islands and other shapes using poly(ethylene) glycol as the cell-repulsive material and a collagen/poly-D-lysine (PDL) mixture as the cell-adhesive material. We show that dissociated rat hippocampal neurons and glia grown at low densities on such patterns retain strong pattern adherence for over 25 days. The patterned neurons are comparable to control, un-patterned cells in electrophysiological properties and in immunocytochemical measurements of synaptic density and inhibitory cell distributions. We suggest that an inexpensive desktop printer may be an accessible tool for making micro-island cultures and other basic patterns. We also suggest that ink-jet printing may be extended to a range of developmental neuroscience studies, given its ability to more easily layer materials, build substrate-bound gradients, construct out-of-plane structure, and deposit sources of diffusible factors.
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Affiliation(s)
- Neville E Sanjana
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology (MIT), Cambridge, MA, USA
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825
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Fellin T, Carmignoto G. Neurone-to-astrocyte signalling in the brain represents a distinct multifunctional unit. J Physiol 2004; 559:3-15. [PMID: 15218071 PMCID: PMC1665073 DOI: 10.1113/jphysiol.2004.063214] [Citation(s) in RCA: 206] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Astrocytes can respond to neurotransmitters released at the synapse by generating elevations in intracellular Ca(2+) concentration ([Ca(2+)](i)) and releasing glutamate that signals back to neurones. This discovery opens new perspectives for the possible participation of these glial cells in actual information processing by the brain and raises the hypothesis that astrocyte activation by neuronal signals plays a key role in distinct, functional events. Depending on the level of neuronal activity, the [Ca(2+)](i) response that is activated by neurotransmitters can either remain restricted to an astrocytic process or it can propagate as an intracellular [Ca(2+)](i) wave to other astrocytic processes in contact with different neurones, astrocytes, microglia or endothelial cells of cerebral arterioles. Glutamate release triggered by the [Ca(2+)](i) rise at the astrocytic process represents a feedback, short-distance signal that affects synaptic transmission locally. The release of glutamate as well as of other compounds far away from the site of initial activation represents a feedforward, long-distance signal that can be involved in the regulation of distinct processes. For instance, through the release of vasoactive molecules from the astrocytic processes in contact with cerebral arterioles, the neurone-astrocyte-endothelial cell signalling pathway plays a pivotal role in the neuronal control of vascular tone. In this article we will review recent results that should persuade us to reshape our current thinking on the roles of astroglial cells in the brain. We propose that neurones and astrocytes represent an integral unit that has a distinctive role in different fundamental events in brain function. Furthermore, while recent findings provide important evidences for the vesicular hypothesis of glutamate release, we discuss also the proposals for a possible physiological role of hemichannels and purinergic P2X(7) receptors in glutamate release from astrocytes. A full clarification of the functional significance of the bidirectional communication that astrocytes establish with neurones as well as with other brain cells represents one of the most intriguing challenges in neurobiological research at the moment and should fuel stimulating debates in years to come.
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Affiliation(s)
- Tommaso Fellin
- Istituto CNR di Neuroscienze and Dipartimento di Scienze Biomediche Sperimentali, Università di Padova, Viale G. Colombo 3, 35121 Padova, Italy
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826
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Zhang Q, Fukuda M, Van Bockstaele E, Pascual O, Haydon PG. Synaptotagmin IV regulates glial glutamate release. Proc Natl Acad Sci U S A 2004; 101:9441-6. [PMID: 15197251 PMCID: PMC438995 DOI: 10.1073/pnas.0401960101] [Citation(s) in RCA: 176] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2004] [Accepted: 05/07/2004] [Indexed: 11/18/2022] Open
Abstract
Calcium-binding synaptotagmins (Syts) are membrane proteins that are conserved from nematode to human. Fifteen Syts (Syts I-XV) have been identified in mammalian species. Syt I has been well studied and is a candidate for the Ca(2+)-sensor that triggers evoked exocytosis underlying fast synaptic transmission. Whereas the functions of the other Syts are unclear, Syt IV is of particular interest because it is rapidly up-regulated after chronic depolarization or seizures, and because null mutations exhibit deficits in fine motor coordination and hippocampus-dependent memory. Screening Syts I-XIII, which are enriched in brain, we find that Syt IV is located in processes of astroglia in situ. Reduction of Syt IV in astrocytes by RNA interference decreases Ca(2+)-dependent glutamate release, a gliotransmission pathway that regulates synaptic transmission. Mutants of the C2B domain, the only putative Ca(2+)-binding domain in Syt IV, act in a dominant-negative fashion over Ca(2+)-regulated glial glutamate release, but not gliotransmission induced by changes in osmolarity. Because we find that Syt IV is expressed predominantly by astrocytes and is not in the presynaptic terminals of the hippocampus, and because Syt IV knockout mice exhibit hippocampal-based memory deficits, our data raise the intriguing possibility that Syt IV-mediated gliotransmission contributes to hippocampal-based memory.
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Affiliation(s)
- Qi Zhang
- Department of Neuroscience, Room 215, Stemmler Hall, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
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827
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Brockhaus J, Dressel D, Herold S, Deitmer JW. Purinergic modulation of synaptic input to Purkinje neurons in rat cerebellar brain slices. Eur J Neurosci 2004; 19:2221-30. [PMID: 15090048 DOI: 10.1111/j.0953-816x.2004.03325.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Adenosine triphosphate (ATP) is a cotransmitter and an extracellular neuromodulator in nervous systems, and it influences neural circuits and synaptic strength. We have studied a stimulating effect of ATP (100 micro m) on the synaptic input of Purkinje neurons in acute cerebellar brain slices of juvenile rats (p14-19). Bath application of ATP increased the frequency of spontaneous postsynaptic currents (sPSCs) almost twofold, and increased their amplitude. These effects were fully suppressed by the P2 receptor antagonist pyridoxalphosphate-6-azophenyl-2'4'-disulphonic acid (PPADS; 10 microm), or after blocking action potentials with tetrodotoxin (TTX; 0.5 microm), but were not impaired by inhibiting ionotropic, non-NMDA glutamate receptors with 2,3-dioxo-6-nitro-1,2,3,4,-tetrahydrobenzo[f]quinoxaline-7-sulphonamide (NBQX; 5 microm). The frequency of sPSCs was reduced by 35% by PPADS and increased by 50% after inhibiting ectonucleotidase with ARL67156 (50 microm), suggesting intrinsic, 'tonic', stimulation of synaptic activity via P2 receptors. The pharmacological profile indicated that the ATP effect was mediated by both P2X and P2Y receptors, most probably of the P2X5- and P2Y(2,4)-like subtypes. The action potential frequency in the inhibitory basket cells was increased by 65%, and decreased in Purkinje neurons by 25%, in the presence of ATP. Our results suggest that ATP continuously modulates the cerebellar circuit by increasing the activity of inhibitory input to Purkinje neurons, and thus decreasing the main cerebellar output activity, which contributes to locomotor coordination.
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Affiliation(s)
- Johannes Brockhaus
- Abteilung Allgemeine Zoologie, Fachbereich Biologie, Universität Kaiserslautern, Erwin-Schrödinger-Strasse 13, 67663 Kaiserslautern, Germany.
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828
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Ahmed T, Frey S, Frey JU. Regulation of the phosphodiesterase PDE4B3-isotype during long-term potentiation in the area dentata in vivo. Neuroscience 2004; 124:857-67. [PMID: 15026126 DOI: 10.1016/j.neuroscience.2004.01.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/07/2004] [Indexed: 11/28/2022]
Abstract
Hippocampal long-term potentiation (LTP) is the most prominent cellular model underlying learning and memory formation. However, which cellular processes are involved in maintaining LTP remains largely unknown. We have previously detailed temporal modulations of cyclic adenosine monophosphate (cAMP) and a cAMP-specific phosphodiesterase, PDE4B3, after LTP-induction and its maintenance in hippocampal area CA1 in vitro. To test whether other hippocampal sub-structures are characterised by similar mechanisms, tissue from the area dentata of freely moving rats was analysed at different LTP-time points. The tissue was fractionated into three components, where PDE4B-levels and cAMP-concentrations were measured. In contrast with data obtained in area CA1, we now detail an LTP-specific translational, but not transcriptional regulation of PDE4B3 within the first 8 h after tetanization and present spatio-temporal changes of PDE4B proteins and cAMP that is LTP-specific.
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Affiliation(s)
- T Ahmed
- Leibniz-Institute for Neurobiology, Department of Neurophysiology, Brenneckestrasse 6, D-39118 Magdeburg, Germany
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829
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Harrison PJ. The hippocampus in schizophrenia: a review of the neuropathological evidence and its pathophysiological implications. Psychopharmacology (Berl) 2004; 174:151-62. [PMID: 15205886 DOI: 10.1007/s00213-003-1761-y] [Citation(s) in RCA: 518] [Impact Index Per Article: 25.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2003] [Accepted: 11/25/2003] [Indexed: 01/17/2023]
Abstract
This paper puts the case for the hippocampus as being central to the neuropathology and pathophysiology of schizophrenia. The evidence comes from a range of approaches, both in vivo (neuropsychology, structural and functional imaging) and post mortem (histology, morphometry, gene expression, and neurochemistry). Neuropathologically, the main positive findings concern neuronal morphology, organisation, and presynaptic and dendritic parameters. The results are together suggestive of an altered synaptic circuitry or "wiring" within the hippocampus and its extrinsic connections, especially with the prefrontal cortex. These changes plausibly represent the anatomical component of the aberrant functional connectivity that underlies schizophrenia. Glutamatergic pathways are prominently but not exclusively affected. Changes appear somewhat greater in the left hippocampus than the right, and CA1 is relatively uninvolved compared to other subfields. Hippocampal pathology in schizophrenia may be due to genetic factors, aberrant neurodevelopment, and/or abnormal neural plasticity; it is not due to any recognised neurodegenerative process. Hippocampal involvement is likely to be associated with the neuropsychological impairments of schizophrenia rather than with its psychotic symptoms.
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Affiliation(s)
- Paul J Harrison
- Department of Psychiatry, Neurosciences Building, Warneford Hospital, University of Oxford, Oxford, OX3 7JX, UK.
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830
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Abstract
The Eph receptors are a large family of receptor tyrosine kinases with important roles in the establishment of neuronal and vascular networks during embryonic development. The functions of Eph receptors in the adult brain have only recently been investigated, and the results are forcing us to amend the conventional view that these molecules function predominantly in a developmental context. This review summarizes this rapidly expanding new area of research, which has shown that the Eph receptors regulate the structure and physiological function of excitatory synapses through multiple mechanisms, and might thus play a significant role in higher brain functions.
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Affiliation(s)
- Yu Yamaguchi
- Developmental Neurobiology Program, The Burnham Institute, 10901 North Torrey Pines Road, La Jolla, California 92037, USA.
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831
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Benz B, Grima G, Do KQ. Glutamate-induced homocysteic acid release from astrocytes: possible implication in glia-neuron signaling. Neuroscience 2004; 124:377-86. [PMID: 14980387 DOI: 10.1016/j.neuroscience.2003.08.067] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2002] [Revised: 08/13/2003] [Accepted: 08/22/2003] [Indexed: 11/30/2022]
Abstract
Glial cells synthesise neuroactive substances and release them upon neurotransmitter receptor activation. Homocysteic acid (HCA), an endogenous agonist for glutamatergic N-methyl-D-aspartate (NMDA) receptors, is predominantly localised in glial cells. We have previously demonstrated the release of HCA from mouse astrocytes in culture following activation of beta-adrenergic receptors. Moreover, a release of HCA has also been observed in vivo upon physiological stimulation of sensory afferents in the thalamus. Here we report the glutamate-induced release of HCA from astrocytes. The effect of glutamate was mediated by the activation of ionotropic (NMDA and non-NMDA) as well as by metabotropic receptors. In addition, the release of HCA was Ca(2+)- and Na(+)-dependent, and its mechanism involved the activation of the Na+/Ca(2+)-exchanger. Furthermore, we provide evidence for the presence of functional NMDA receptors on astrocytes, which are coupled to an intracellular Ca2+ increase via stimulation of the Na+/Ca(2+)-exchanger. Our data thus favour a participation of glial cells in excitatory neurotransmission and corroborate the role of HCA as a "gliotransmitter."
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Affiliation(s)
- B Benz
- Centre for Research in Psychiatric Neuroscience, Department of Psychiatry, University of Lausanne, Route de Cery, CH-1008 Prilly-Lausanne, Switzerland
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832
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Gale JE, Piazza V, Ciubotaru CD, Mammano F. A mechanism for sensing noise damage in the inner ear. Curr Biol 2004; 14:526-9. [PMID: 15043820 DOI: 10.1016/j.cub.2004.03.002] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2003] [Revised: 02/03/2004] [Accepted: 02/06/2004] [Indexed: 11/26/2022]
Abstract
Our sense of hearing requires functional sensory hair cells. Throughout life those hair cells are subjected to various traumas, the most common being loud sound. The primary effect of acoustic trauma is manifested as damage to the delicate mechanosensory apparatus of the hair cell stereocilia. This may eventually lead to hair cell death and irreversible deafness. Little is known about the way in which noxious sound stimuli affect individual cellular components of the auditory sensory epithelium. However, studies in different types of cell cultures have shown that damage and mechanical stimulation can activate changes in intracellular free calcium concentration ([Ca(2+)](i)) and elicit intercellular Ca(2+) waves. Thus an attractive hypothesis is that changes in [Ca(2+)](i), propagating as a wave through support cells in the organ of Corti, may constitute a fundamental mechanism to signal the occurrence of hair cell damage. The mechanism we describe here exhibits nanomolar sensitivity to extracellular ATP, involves regenerative propagation of intercellular calcium waves due to ATP originating from hair cells, and depends on functional IP(3)-sensitive intracellular stores in support cells.
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Affiliation(s)
- Jonathan E Gale
- Department of Physiology and Centre for Auditory Research, University College London, Gower Street, London, WC1E 6BT, United Kingdom.
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833
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Altevogt BM, Paul DL. Four classes of intercellular channels between glial cells in the CNS. J Neurosci 2004; 24:4313-23. [PMID: 15128845 PMCID: PMC6729442 DOI: 10.1523/jneurosci.3303-03.2004] [Citation(s) in RCA: 129] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2003] [Revised: 02/03/2004] [Accepted: 03/09/2004] [Indexed: 11/21/2022] Open
Abstract
Astrocytes form extensive gap junctions with other astrocytes and with oligodendrocytes. Junctional communication between CNS glia is likely of critical importance because loss of the gap junction channel-forming proteins, connexins Cx32 and Cx47, result in severe demyelination. However, CNS glia express at least six connexins, and the cellular origins and relationships of these proteins have not been determined. We produced a Cx29 reporter mouse in which the connexin coding sequence was replaced with a histological marker, which was used to demonstrate that Cx29, Cx32, and Cx47 are expressed specifically in oligodendrocytes. To determine the relationships between astrocyte and oligodendrocyte connexins, we used double- and triple-immunofluorescence microscopy using semithin sections (<1 microm) of adult mouse spinal cord. Astrocytes form two distinct classes of gap junctions with each other; those composed of Cx26 and those composed of Cx43 and Cx30. In addition, astrocytes establish two classes of intercellular channels with oligodendrocytes, heterotypic Cx26-Cx32 channels and heterotypic Cx30/Cx43-Cx47 channels that may also be heteromeric. In contrast, Cx29 does not colocalize with any of the other five connexins. The data provide the first in vivo demonstration of heterotypic intercellular channels and reveal an unexpected complexity in the composition of glial gap junctions.
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Affiliation(s)
- Bruce M Altevogt
- Program in Neuroscience and Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, USA
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834
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Tenschert S, Reinert A, Hoheisel U, Mense S. Effects of a chronic myositis on structural and functional features of spinal astrocytes in the rat. Neurosci Lett 2004; 361:196-9. [PMID: 15135927 DOI: 10.1016/j.neulet.2003.12.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The study aimed at the question if astrocytes react with morphological or functional changes when a skeletal muscle is pathologically altered. In rats, a myositis was induced in the gastrocnemius-soleus muscle. After 12 days, the immunoreactivity (IR) for glial fibrillary acidic protein (GFAP), morphometric parameters, and fibroblast growth factor-2 (FGF-2) expression of astrocytes were quantitatively evaluated in the dorsal horn of the spinal segment L4. Following inflammation, the area density of GFAP-IR as well as the proportion of astrocytes expressing FGF-2 increased significantly while the degree of astrocyte arborisation decreased as shown by a shape factor. The density of cell nuclei was unchanged suggesting that no myositis-induced cell divisions occurred. The data indicate that spinal astrocytes may influence pain processes particularly by increased FGF-2 synthesis.
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Affiliation(s)
- S Tenschert
- Institut für Anatomie und Zellbiologie, Universität Heidelberg, Im Neuenheimer Feld 307, D-69120 Heidelberg, Germany
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835
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Audette JF, Wang F, Smith H. Bilateral Activation of Motor Unit Potentials with Unilateral Needle Stimulation of Active Myofascial Trigger Points. Am J Phys Med Rehabil 2004; 83:368-74, quiz 375-7, 389. [PMID: 15100626 DOI: 10.1097/01.phm.0000118037.61143.7c] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE The objective of this study was to determine if there are electromyographic differences between active and latent myofascial trigger points (MTrPs) during trigger point needling. DESIGN A total of 21 subjects were recruited prospectively. The experimental group consisted of 13 subjects who had active myofascial pain in the neck for >6 mos. The age-matched, control group consisted of eight subjects without neck pain but with taut bands in the cervical musculature. The active MTrPs (or latent MTrPs in the control group) were identified in the trapezius or levator scapulae muscles, then needle electrodes were inserted ipsilaterally into the muscle with the MTrPs and into the same muscle on the contralateral side. Electromyographic activity was recorded bilaterally with a dual-channel electromyographic machine, and local twitch responses were obtainedusinganacupuncturedryneedlingtechniqueonlyonthesideoftheactiveMTrPs. RESULTS We demonstrated that in subjects with active MTrPs, bilateral motor unit activation could be obtained with unilateral needle stimulation of the trigger point. In contrast, in all the subjects with latent MTrPs, only unilateral motor unit activation could be obtained in the muscle on the same side of the needle stimulation. The motor unit potentials seen on the electromyograph were similar in morphology to a fasciculation potential but more complex. CONCLUSION We demonstrated bilateral or mirror-image electromyographic activity associated with unilateral needle stimulation of active MTrPs. We have found no previous mention of this phenomenon in the literature. Our study supports the concept that the perpetuation of pain and muscle dysfunction in active MTrPs may be related to abnormal central nervous system processing of sensory input at the level of the spinal cord.
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Affiliation(s)
- Joseph F Audette
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, Massachusetts, USA
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836
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Blomstrand F, Venance L, Sirén AL, Ezan P, Hanse E, Glowinski J, Ehrenreich H, Giaume C. Endothelins regulate astrocyte gap junctions in rat hippocampal slices. Eur J Neurosci 2004; 19:1005-15. [PMID: 15009148 DOI: 10.1111/j.0953-816x.2004.03197.x] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Gap junctional communication (GJC) is a typical feature of astrocytes proposed to contribute to the role played by these glial cells in brain physiology and pathology. In acutely isolated hippocampal slices from rat (P11-P19), intercellular diffusion of biocytin through gap junction channels was shown to occur between hundreds of cells immuno-positive for astrocytic markers studied in the CA1/CA2 region. Single-cell RT-PCR demonstrated astrocytic mRNA expression of several connexin (Cx) subtypes, the molecular constituent of gap junction channels, whereas immunoblotting confirmed that Cx43 and Cx30 are the main gap junction proteins in hippocampal astrocytes. In the brain, astrocytes represent a major target for endothelins (Ets), a vasoactive family of peptides. Our results demonstrate that Ets decrease the expression of phosphorylated Cx43 forms and are potent inhibitors of GJC. The Et-induced effects were investigated using specific Et receptor agonists and antagonists, including Bosentan (Tracleer trade mark ), an EtA/B receptor antagonist, and using hippocampal slices and cultures from EtB-receptor-deficient rats. Interestingly, the pharmacological profile of Ets effects did not follow the classical profile established in cardiovascular systems. The present study therefore identifies Ets as potent endogenous inhibitory regulators of astrocyte networks. As such, the action of these peptides on astrocyte GJC might be involved in the contribution of astrocytes to neuroprotective processes and have a therapeutic potential in neuropathological situations.
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Affiliation(s)
- F Blomstrand
- Neuropharmacologie, INSERM U114, Collège de France, Paris, France.
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837
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D'Ascenzo M, Vairano M, Andreassi C, Navarra P, Azzena GB, Grassi C. Electrophysiological and molecular evidence of L-(Cav1), N- (Cav2.2), and R- (Cav2.3) type Ca2+ channels in rat cortical astrocytes. Glia 2004; 45:354-63. [PMID: 14966867 DOI: 10.1002/glia.10336] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Changes in intracellular Ca2+ levels are an important signal underlying neuron-glia cross-talk, but little is known about the possible role of voltage-gated Ca2+ channels (VGCCs) in controlling glial cell Ca2+ influx. We investigated the pharmacological and biophysical features of VGCCs in cultured rat cortical astrocytes. In whole-cell patch-clamp experiments, L-channel blockade (5 microM nifedipine) reduced Ba2+ current amplitude by 28% of controls, and further decrease (32%) was produced by N-channel blockade (3 microM omega-conotoxin-GVIA). No significant additional changes were observed after P/Q channel blockade (3 microM omega-conotoxin-MVIIC). Residual current (36% of controls) amounted to roughly the same percentage (34%) that was abolished by R-channel blockade (100 nM SNX-482). Electrophysiological evidence of L-, N-, and R-channels was associated with RT-PCR detection of mRNA transcripts for VGCC subunits alpha1C (L-type), alpha1B (N-type), and alpha1E (R-type). In cell-attached recordings, single-channel properties (L-currents: amplitude, -1.21 +/- 0.02 pA at 10 mV; slope conductance, 22.0 +/- 1.1 pS; mean open time, 5.95 +/- 0.24 ms; N-currents: amplitude, -1.09 +/- 0.02 pA at 10 mV; slope conductance, 18.0 +/- 1.1 pS; mean open time, 1.14 +/- 0.02 ms; R-currents: amplitude, -0.81 +/- 0.01 pA at 20 mV; slope conductance, 10.5 +/- 0.3 pS; mean open time, 0.88 +/- 0.02 ms) resembled those of corresponding VGCCs in neurons. These novel findings indicate that VGCC expression by cortical astrocytes may be more varied than previously thought, suggesting that these channels may indeed play substantial roles in the regulation of astrocyte Ca2+ influx, which influences neuron-glia cross-talk and numerous other calcium-mediated glial-cell functions.
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MESH Headings
- Animals
- Astrocytes/drug effects
- Astrocytes/physiology
- Calcium Channel Blockers/pharmacology
- Calcium Channels, L-Type/biosynthesis
- Calcium Channels, L-Type/genetics
- Calcium Channels, L-Type/physiology
- Calcium Channels, N-Type/biosynthesis
- Calcium Channels, N-Type/genetics
- Calcium Channels, N-Type/physiology
- Calcium Channels, R-Type/biosynthesis
- Calcium Channels, R-Type/genetics
- Calcium Channels, R-Type/physiology
- Cells, Cultured
- Cerebral Cortex/drug effects
- Cerebral Cortex/physiology
- Electrophysiology
- Rats
- Rats, Wistar
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Affiliation(s)
- Marcello D'Ascenzo
- Institute of Human Physiology, Medical School, Catholic University S. Cuore, Rome, Italy
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838
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McCarthy MM, Todd BJ, Amateau SK. Estradiol modulation of astrocytes and the establishment of sex differences in the brain. Ann N Y Acad Sci 2004; 1007:283-97. [PMID: 14993061 DOI: 10.1196/annals.1286.027] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The role of steroid hormones as a conduit for reciprocal glial-neuronal communication is an emerging but relatively unexplored concept. Research in our laboratory has discovered that the relationship between astrocytic and neuronal morphology during development is distinct for different brain regions and provides a fundamental basis for region-specific sexual differentiation. The functional significance of estradiol-induced differentiation of astrocytes and the cross-talk of these cells with neurons includes permanent changes in synaptic patterning and control of adult reproductive behaviors. The cellular mechanisms as currently understood for each region are discussed and unanswered questions as well as other areas for future research are reviewed.
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Affiliation(s)
- M M McCarthy
- Department of Physiology and Program in Neuroscience, University of Maryland, Baltimore, School of Medicine, Baltimore, Maryland 21201, USA.
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839
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Lee J, Auyeung WW, Mattson MP. Interactive effects of excitotoxic injury and dietary restriction on microgliosis and neurogenesis in the hippocampus of adult mice. Neuromolecular Med 2004; 4:179-96. [PMID: 14716025 DOI: 10.1385/nmm:4:3:179] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2003] [Accepted: 07/03/2003] [Indexed: 01/17/2023]
Abstract
Responses to neuronal degeneration are complex, involving activation of microglia, astrocytes, and synaptic remodeling. It has also been suggested that neuronal injury stimulates neurogenesis, the production of new neurons from neural stem cells. Because dietary restriction (DR) can increase hippocampal neurogenesis and promotes the survival of neurons following injury, we determined the effects of DR on the responses of neural stem cells, microglia, and astrocytes in the hippocampus to seizure-induced hippocampal damage. Mice on ad libitum or DR diets were given an intrahippocampal injection of kainate, administered the DNA precursor bromodeoxyuridine (BrdU) during a 5-d period, and euthanized 1 d or 3 wk later. Although kainate greatly increased the numbers of BrdU-labeled cells, it did not enhance neurogenesis and damaged neurons were not replaced. Instead, most BrdU-labeled cells were either proliferating microglia or neural progenitor cells that subsequently died. Microgliosis was transient and was strongly correlated with the amount of damage to CA3 neurons, whereas astrocytosis was delayed and not correlated with neuronal loss. Surprisingly, neurogenesis was not increased in response to seizure-induced damage, and although DR increased basal neurogenesis, it did not promote neurogenesis following brain injury. DR significantly decreased seizure-induced microgliosis, but did not affect astrocytosis. Our findings show that DR suppresses injuryinduced microgliosis suggesting a contribution of a reduced microglial response to the neuroprotective effects of DR.
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Affiliation(s)
- Jaewon Lee
- Laboratory of Neurosciences, National Institute on Aging Gerontology Research Center, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA
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840
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Wilhelm A, Volknandt W, Langer D, Nolte C, Kettenmann H, Zimmermann H. Localization of SNARE proteins and secretory organelle proteins in astrocytes in vitro and in situ. Neurosci Res 2004; 48:249-57. [PMID: 15154671 DOI: 10.1016/j.neures.2003.11.002] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2003] [Accepted: 11/13/2003] [Indexed: 11/30/2022]
Abstract
Astrocytes are capable of regulated release of messenger molecules. Astrocytes cultured from new born rodent brain express a variety of classical presynaptic proteins. We investigated the question whether the capability to express synaptic proteins in culture was a feature only of immature astrocytes, and whether these proteins were also expressed by astrocytes in situ. Experiments were performed with transgenic mice expressing the enhanced green fluorescent protein under the control of the human glial fibrillary acidic protein promoter. Using double fluorescence and astrocytes cultured from 1 to 16 day-old animals we show that the astrocytic expression of synaptic proteins in culture is invariant of the age of donor animals. Culturing can induce the astrocytic expression of specific synaptic proteins such as SV2, synaptophysin and SNAP-25. Astrocytes in brain sections of 1-16 day-old animals revealed a punctuate immunofluorescence for secretory carrier membrane protein (SCAMP), SNAP-23, synaptobrevin II, and cellubrevin, to a minor extent for SNAP-25 and synaptophysin, and none for SV2. Our results demonstrate that cultured astrocytes express synaptic proteins not present in situ. Nevertheless, astrocytic organelles in situ are equipped with molecules that could be involved in regulated exocytosis of messenger substances.
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Affiliation(s)
- Alexander Wilhelm
- Biozentrum der J. W Goethe-Universität, AK Neurochemie, Zoologisches Institut, Marie-Curie-Str 9, D-60439 Frankfurt am Main, Germany
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841
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Kercel SW. THE ROLE OF VOLUME TRANSMISSION IN AN ENDOGENOUS BRAIN. J Integr Neurosci 2004; 3:7-18. [PMID: 15139075 DOI: 10.1142/s0219635204000348] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2003] [Accepted: 01/26/2004] [Indexed: 11/18/2022] Open
Abstract
Brain dynamics depends on synaptic, diffusive, and glial activities. Observations indicate that synaptic and diffusive activities modify each other's morphology, and glial activity modifies both. Synaptic activity modifies glial morphology. Whether diffusion modifies glial morphology has not been reported but it is reasonable to expect that it does. The relationship between these three transmission processes forms a closed-loop hierarchy of causation in brain dynamics, and the operation of that hierarchy may account for some of the seemingly bizarre properties of cognitive function.
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Affiliation(s)
- Stephen W Kercel
- University of New England, 2 Brian Drive, Brunswick, ME 04011, USA.
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842
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Zarate CA, Du J, Quiroz J, Gray NA, Denicoff KD, Singh J, Charney DS, Manji HK. Regulation of cellular plasticity cascades in the pathophysiology and treatment of mood disorders: role of the glutamatergic system. Ann N Y Acad Sci 2004; 1003:273-91. [PMID: 14684452 DOI: 10.1196/annals.1300.017] [Citation(s) in RCA: 139] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
There is increasing evidence from a variety of sources that mood disorders are associated with regional reductions in brain volume, as well as reductions in the number, size, and density of glia and neurons in discrete brain areas. Although the precise pathophysiology underlying these morphometric changes remains to be fully elucidated, the data suggest that severe mood disorders are associated with impairments of structural plasticity and cellular resilience. In this context, it is noteworthy that a growing body of data suggests that the glutamatergic system--which is known to play a major role in neuronal plasticity and cellular resilience--may be involved in the pathophysiology and treatment of mood disorders. Preclinical studies have shown that the glutamatergic system represents targets (often indirect) for the actions of antidepressants and mood stabilizers. There are a number of glutamatergic "plasticity enhancing" strategies that may be of considerable utility in the treatment of mood disorders. Among the most immediate ones are NMDA antagonists, inhibitors of glutamate-release agents, and AMPA potentiators; this research progress holds much promise for the development of novel therapeutics for the treatment of severe, refractory mood disorders.
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Affiliation(s)
- Carlos A Zarate
- Laboratory of Molecular Pathophysiology, Mood and Anxiety Disorders Program, National Institute of Mental Health, Bethesda, Maryland 20892, USA.
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843
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Pape HC, Munsch T, Budde T. Novel vistas of calcium-mediated signalling in the thalamus. Pflugers Arch 2004; 448:131-8. [PMID: 14770314 DOI: 10.1007/s00424-003-1234-5] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2003] [Accepted: 12/12/2003] [Indexed: 11/29/2022]
Abstract
Traditionally, the role of calcium ions (Ca(2+)) in thalamic neurons has been viewed as that of electrical charge carriers. Recent experimental findings in thalamic cells have only begun to unravel a highly complex Ca(2+) signalling network that exploits extra- and intracellular Ca(2+) sources. In thalamocortical relay neurons, interactions between T-type Ca(2+) channel activation, Ca(2+)-dependent regulation of adenylyl cyclase activity and the hyperpolarization-activated cation current ( I(h)) regulate oscillatory burst firing during periods of sleep and generalized epilepsy, while a functional triad between Ca(2+) influx through high-voltage-activated (most likely L-type) Ca(2+) channels, Ca(2+)-induced Ca(2+) release via ryanodine receptors (RyRs) and a repolarizing mechanism (possibly via K(+) channels of the BK(Ca) type) supports tonic spike firing as required during wakefulness. The mechanisms seem to be located mostly at dendritic and somatic sites, respectively. One functional compartment involving local GABAergic interneurons in certain thalamic relay nuclei is the glomerulus, in which the dendritic release of GABA is regulated by Ca(2+) influx via canonical transient receptor potential channels (TRPC), thereby presumably enabling transmitters of extrathalamic input systems that are coupled to phospholipase C (PLC)-activating receptors to control feed-forward inhibition in the thalamus. Functional interplay between T-type Ca(2+) channels in dendrites and the A-type K(+) current controls burst firing, contributing to the range of oscillatory activity observed in these interneurons. GABAergic neurons in the reticular thalamic (RT) nucleus recruit a specific set of Ca(2+)-dependent mechanisms for the generation of rhythmic burst firing, of which a particular T-type Ca(2+) channel in the dendritic membrane, the Ca(2+)-dependent activation of non-specific cation channels ( I(CAN)) and of K(+) channels (SK(Ca) type) are key players. Glial Ca(2+) signalling in the thalamus appears to be a basic mechanism of the dynamic and integrated exchange of information between glial cells and neurons. The conclusion from these observations is that a localized calcium signalling network exists in all neuronal and probably also glial cell types in the thalamus and that this network is dedicated to the precise regulation of the functional mode of the thalamus during various behavioural states.
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Affiliation(s)
- Hans-Christian Pape
- Institut für Physiologie, Medizinische Fakultät, Otto-von-Guericke-Universität Magdeburg, Leipziger Strasse 44, 39120, Magdeburg, Germany.
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844
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Hama H, Hara C, Yamaguchi K, Miyawaki A. PKC Signaling Mediates Global Enhancement of Excitatory Synaptogenesis in Neurons Triggered by Local Contact with Astrocytes. Neuron 2004; 41:405-15. [PMID: 14766179 DOI: 10.1016/s0896-6273(04)00007-8] [Citation(s) in RCA: 228] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2003] [Revised: 12/02/2003] [Accepted: 12/29/2003] [Indexed: 11/29/2022]
Abstract
Here we provide evidence that astrocytes affect neuronal synaptogenesis by the process of adhesion. Local contact with astrocytes via integrin receptors elicited protein kinase C (PKC) activation in individual dissociated neurons cultured in astrocyte-conditioned medium. This activation, initially focal, soon spread throughout the entire neuron. We then demonstrated pharmacologically that the arachidonic acid cascade, triggered by the integrin reception, is responsible for the global activation of PKC. Local astrocytic contact also facilitated excitatory synaptogenesis throughout the neuron, a process which could be blocked by inhibitors of both integrins and PKC. Thus, propagation of PKC signaling represents an underlying mechanism for global neuronal maturation following local astrocyte adhesion.
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Affiliation(s)
- Hiroshi Hama
- Laboratory for Cell Function Dynamics, Advanced Technology Development Group, Brain Science Institute, RIKEN, Wako-City, Saitama, Japan
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845
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Engelman HS, MacDermott AB. Presynaptic ionotropic receptors and control of transmitter release. Nat Rev Neurosci 2004; 5:135-45. [PMID: 14735116 DOI: 10.1038/nrn1297] [Citation(s) in RCA: 173] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Holly S Engelman
- Department of Physiology and Cellular Biophysics and the Center for Neurobiology and Behavior, Columbia University, New York, USA
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846
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Zhu Y, Kimelberg HK. Cellular expression of P2Y and beta-AR receptor mRNAs and proteins in freshly isolated astrocytes and tissue sections from the CA1 region of P8-12 rat hippocampus. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2004; 148:77-87. [PMID: 14757521 DOI: 10.1016/j.devbrainres.2003.10.014] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Although almost all GFAP(+) cells in primary astrocyte cultures show functional beta-adrenergic (beta-AR) and metabotropic purinergic (P2Y) receptors, the fewer studies on astrocytes in situ have shown that a much smaller proportion express these same receptor-mediated activities. Here we show, by multiplex single cell RT-PCR, that 44% of freshly isolated, GFAP(+) astrocytes (FIAs) from the CA1 of P8-12 rat hippocampus always co-express beta-adrenergic receptor mRNA subtypes with metabotropic ATP receptor mRNA subtypes (P2Y1, P2Y2 or P2Y4). We also found that beta2 mRNA was the dominant beta-AR subtype expressed. P2Y1 mRNA always co-expresses with either one or two subtypes of P2U-like receptor (P2Y2 or P2Y4) mRNAs. Immunocytochemical studies showed a similar percentage of all FIAs expressed beta-AR and P2Y1 protein (54% and 52%, respectively), as for the mRNAs (46% and 65%, respectively). The staining of hippocampal sections for beta-AR or P2Y1 receptor plus GFAP shows that there are quite numerous, scattered star-shaped GFAP(+) astrocytes in the CA1 region of P9-10 rat hippocampus that stained positive for either of these receptors. These data show that astrocytes in situ express, and to a large extent likely co-express, beta-AR and P2Y receptors.
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Affiliation(s)
- Yingzi Zhu
- Center for Neuropharmacology and Neuroscience, USA
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847
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Yonezawa T, Ohtsuka A, Yoshitaka T, Hirano S, Nomoto H, Yamamoto K, Ninomiya Y. Limitrin, a novel immunoglobulin superfamily protein localized to glia limitans formed by astrocyte endfeet. Glia 2004; 44:190-204. [PMID: 14603461 DOI: 10.1002/glia.10279] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
We report the molecular cloning of a new member of the transmembrane-type immunoglobulin superfamily and designate the encoded protein as limitrin, since it localized selectively to glia limitans in mouse brain. Limitrin cDNA was obtained using a subtractive hybridization procedure designed to identify molecules responsible for blood-brain barrier function. Western blots using a limitrin-specific antibody demonstrated that the gene product is expressed significantly in mouse brain and primary murine astrocytes and is distributed in the plasma membrane. Immunohistochemical studies using confocal and electron microscopy clearly demonstrated highly polarized localization in astroglial endfeet in the perivascular region and under the pia mater in vivo. Limitrin is expressed in the spinal cord and in many areas of the brain, but not in the median eminence or subfornical organ (the circumventricular organs), where the blood-brain barrier is lacking. Disruption of the blood-brain barrier by cold injury resulted in a drastic reduction in limitrin expression. Furthermore, during retrieval from cold injury, the increased expression of limitrin in perivascular endfeet correlated with the recovery of angiogenesis in capillaries within the lesion margins. Our results suggest that limitrin is physically and functionally associated with the blood-brain barrier, implying that this protein may be useful as a diagnostic tool of barrier integrity.
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Affiliation(s)
- Tomoko Yonezawa
- Department of Molecular Biology and Biochemistry, Neuroscience and Functional Physiology, Biophysiological Science, Okayama University Graduate School of Medicine and Dentistry, Okayama, Japan
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848
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Abstract
Hydrogen sulfide (H2S) modifies hippocampal long-term potentiation (LTP) and functions as a neuromodulator. Here, we show that H2S increases intracellular Ca2+ and induces Ca2+ waves in primary cultures of astrocytes as well as hippocampal slices. H2S increases the influx of Ca2+ and to a lesser extent causes the release from intracellular Ca2+ stores. Ca2+ waves induced by neuronal excitation as well as responses to exogenously applied H2S are potently blocked by La3+ and Gd3+, inhibitors of Ca2+ channels. These observations suggest that H2S induces Ca2+ waves that propagate to neighboring astrocytes.
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Affiliation(s)
- Yasuo Nagai
- National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo, Japan
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849
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Zhang Q, Pangrsic T, Kreft M, Krzan M, Li N, Sul JY, Halassa M, Van Bockstaele E, Zorec R, Haydon PG. Fusion-related release of glutamate from astrocytes. J Biol Chem 2004; 279:12724-33. [PMID: 14722063 DOI: 10.1074/jbc.m312845200] [Citation(s) in RCA: 192] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Although cell culture studies have implicated the presence of vesicle proteins in mediating the release of glutamate from astrocytes, definitive proof requires the identification of the glutamate release mechanism and the localization of this mechanism in astrocytes at synaptic locales. In cultured murine astrocytes we show an array of vesicle proteins, including SNARE proteins, and vesicular glutamate transporters that are required to fill vesicles with glutamate. Using immunocytochemistry and single-cell multiplex reverse transcription-PCR we demonstrate the presence of these proteins and their transcripts within astrocytes freshly isolated from the hippocampus. Moreover, immunoelectron microscopy demonstrates the presence of VGLUT1 in processes of astrocytes of the hippocampus. To determine whether calcium-dependent glutamate release is mediated by exocytosis, we expressed the SNARE motif of synaptobrevin II to prevent the formation of SNARE complexes, which reduces glutamate release from astrocytes. To further determine whether vesicular exocytosis mediates calcium-dependent glutamate release from astrocytes, we performed whole cell capacitance measurements from individual astrocytes and demonstrate an increase in whole cell capacitance, coincident with glutamate release. Together, these data allow us to conclude that astrocytes in situ express vesicle proteins necessary for filling vesicles with the chemical transmitter glutamate and that astrocytes release glutamate through a vesicle- or fusion-related mechanism.
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Affiliation(s)
- Qi Zhang
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
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850
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Zhang JM, Wang HK, Ye CQ, Ge W, Chen Y, Jiang ZL, Wu CP, Poo MM, Duan S. ATP released by astrocytes mediates glutamatergic activity-dependent heterosynaptic suppression. Neuron 2004; 40:971-82. [PMID: 14659095 DOI: 10.1016/s0896-6273(03)00717-7] [Citation(s) in RCA: 479] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Extracellular ATP released from axons is known to assist activity-dependent signaling between neurons and Schwann cells in the peripheral nervous system. Here we report that ATP released from astrocytes as a result of neuronal activity can also modulate central synaptic transmission. In cultures of hippocampal neurons, endogenously released ATP tonically suppresses glutamatergic synapses via presynaptic P2Y receptors, an effect that depends on the presence of cocultured astrocytes. Glutamate release accompanying neuronal activity also activates non-NMDA receptors of nearby astrocytes and triggers ATP release from these cells, which in turn causes homo- and heterosynaptic suppression. In CA1 pyramidal neurons of hippocampal slices, a similar synaptic suppression was also produced by adenosine, an immediate degradation product of ATP released by glial cells. Thus, neuron-glia crosstalk may participate in activity-dependent synaptic modulation.
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Affiliation(s)
- Jing-ming Zhang
- Institute of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200031 China
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