title: An excitatory loop with astrocytes contributes to drive neurons to seizure threshold.
abstract: Seizures in focal epilepsies are sustained by a highly synchronous neuronal discharge that arises at restricted brain sites and subsequently spreads to large portions of the brain. Despite intense experimental research in this field, the earlier cellular events that initiate and sustain a focal seizure are still not well defined. Their identification is central to understand the pathophysiology of focal epilepsies and to develop new pharmacological therapies for drug-resistant forms of epilepsy. The prominent involvement of astrocytes in ictogenesis was recently proposed. We test here whether a cooperation between astrocytes and neurons is a prerequisite to support ictal (seizure-like) and interictal epileptiform events. Simultaneous patch-clamp recording and Ca2+ imaging techniques were performed in a new in vitro model of focal seizures induced by local applications of N-methyl-D-aspartic acid (NMDA) in rat entorhinal cortex slices. We found that a Ca2+ elevation in astrocytes correlates with both the initial development and the maintenance of a focal, seizure-like discharge. A delayed astrocyte activation during ictal discharges was also observed in other models (including the whole in vitro isolated guinea pig brain) in which the site of generation of seizure activity cannot be precisely monitored. In contrast, interictal discharges were not associated with Ca2+ changes in astrocytes. Selective inhibition or stimulation of astrocyte Ca2+ signalling blocked or enhanced, respectively, ictal discharges, but did not affect interictal discharge generation. Our data reveal that neurons engage astrocytes in a recurrent excitatory loop (possibly involving gliotransmission) that promotes seizure ignition and sustains the ictal discharge. This neuron-astrocyte interaction may represent a novel target to develop effective therapeutic strategies to control seizures.
authors.affiliation: Institute of Neuroscience-Consiglio Nazionale delle Ricerche (CNR), University of Padova, Padova, Italy.
authors.forename: Marta
authors.initials: M
authors.lastname: Gómez-Gonzalo
authors.forename: Gabriele
authors.initials: G
authors.lastname: Losi
authors.forename: Angela
authors.initials: A
authors.lastname: Chiavegato
authors.forename: Micaela
authors.initials: M
authors.lastname: Zonta
authors.forename: Mario
authors.initials: M
authors.lastname: Cammarota
authors.forename: Marco
authors.initials: M
authors.lastname: Brondi
authors.forename: Francesco
authors.initials: F
authors.lastname: Vetri
authors.forename: Laura
authors.initials: L
authors.lastname: Uva
authors.forename: Tullio
authors.initials: T
authors.lastname: Pozzan
authors.forename: Marco
authors.initials: M
authors.lastname: de Curtis
authors.forename: Gian Michele
authors.initials: GM
authors.lastname: Ratto
authors.forename: Giorgio
authors.initials: G
authors.lastname: Carmignoto
mesh_terms: D015761:4-Aminopyridine / Q000378:metabolism; D000200:Action Potentials / Q000502:physiology*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001253:Astrocytes / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D002614:Chelating Agents / Q000378:metabolism; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D018728:Entorhinal Cortex / Q000166:cytology / Q000503:physiopathology; D018690:Excitatory Amino Acid Agonists / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D006168:Guinea Pigs; D051379:Mice; D008822:Mice, Transgenic; D016202:N-Methylaspartate / Q000378:metabolism; D009474:Neurons / Q000502:physiology; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012640:Seizures / Q000503:physiopathology*
chemical_list: D002614:Chelating Agents; D018690:Excitatory Amino Acid Agonists; D026902:Potassium Channel Blockers; D018698:Glutamic Acid; D004533:Egtazic Acid; D016202:N-Methylaspartate; D000255:Adenosine Triphosphate; D015761:4-Aminopyridine; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium
references.citation: Glia. 2000 Jun;30(4):352-61
references.pmid: 10797615
references.citation: Proc Natl Acad Sci U S A. 2005 Apr 12;102(15):5606-11
references.pmid: 15800046
references.citation: Eur J Neurosci. 2000 Jul;12(7):2333-44
references.pmid: 10947812
references.citation: J Neurosci. 1997 Oct 15;17(20):7817-30
references.pmid: 9315902
references.citation: J Neurosci. 2006 Mar 8;26(10):2673-83
references.pmid: 16525046
references.citation: Ann Neurol. 2008 Dec;64(6):674-86
references.pmid: 19107991
references.citation: J Neurosci. 1997 Dec 1;17(23):9308-14
references.pmid: 9364076
references.citation: Mol Neurobiol. 1997 Feb-Apr;14(1-2):1-18
references.pmid: 9170098
references.citation: J Neurosci. 1998 Jun 15;18(12):4637-45
references.pmid: 9614238
references.citation: Nat Methods. 2004 Oct;1(1):31-7
references.pmid: 15782150
references.citation: Proc Natl Acad Sci U S A. 2007 Feb 6;104(6):1995-2000
references.pmid: 17259307
references.citation: J Neurosci. 2006 May 17;26(20):5370-82
references.pmid: 16707789
references.citation: Glia. 2006 Oct;54(5):358-68
references.pmid: 16886201
references.citation: J Neurosci. 2007 Jun 6;27(23):6268-72
references.pmid: 17554000
references.citation: Epilepsy Curr. 2006 Sep-Oct;6(5):173-6
references.pmid: 17260050
references.citation: Brain Res Brain Res Protoc. 1998 Nov;3(2):221-8
references.pmid: 9813340
references.citation: PLoS Biol. 2004 Apr;2(4):E96
references.pmid: 15094801
references.citation: Nat Med. 2005 Sep;11(9):973-81
references.pmid: 16116433
references.citation: J Physiol. 2007 Jun 15;581(Pt 3):1057-81
references.pmid: 17412766
references.citation: Nat Rev Neurosci. 2006 Mar;7(3):194-206
references.pmid: 16495941
references.citation: Science. 2008 Jun 20;320(5883):1638-43
references.pmid: 18566287
references.citation: J Neurosci. 2008 Jun 25;28(26):6659-63
references.pmid: 18579739
references.citation: J Neurosci. 2005 Mar 2;25(9):2192-203
references.pmid: 15745945
references.citation: Epilepsy Res. 2009 Aug;85(2-3):142-9
references.pmid: 19362806
references.citation: Nat Neurosci. 2007 Mar;10(3):331-9
references.pmid: 17310248
references.citation: Nature. 2010 Jan 14;463(7278):232-6
references.pmid: 20075918
references.citation: Neuron. 2004 Sep 2;43(5):729-43
references.pmid: 15339653
references.citation: J Neurophysiol. 1998 Nov;80(5):2727-42
references.pmid: 9819277
references.citation: Sci STKE. 2006 Oct 10;2006(356):re12
references.pmid: 17033045
references.citation: Proc Natl Acad Sci U S A. 2006 Jun 27;103(26):10058-63
references.pmid: 16782808
references.citation: Nat Neurosci. 2006 Jun;9(6):816-23
references.pmid: 16699507
references.citation: Hippocampus. 1994 Feb;4(1):19-35
references.pmid: 7914797
references.citation: J Neurophysiol. 1998 Aug;80(2):978-82
references.pmid: 9705483
references.citation: J Neurosci. 2007 Mar 28;27(13):3383-7
references.pmid: 17392454
references.citation: Epilepsia. 2005 Dec;46(12):1914-25
references.pmid: 16393157
references.citation: Neuroscience. 1997 Nov;81(1):189-97
references.pmid: 9300411
references.citation: J Neurosci. 1996 Aug 15;16(16):5073-81
references.pmid: 8756437
references.citation: J Neurophysiol. 2001 Oct;86(4):1644-51
references.pmid: 11600627
references.citation: Science. 2007 Aug 24;317(5841):1083-6
references.pmid: 17717185
references.citation: Neuroscience. 2008 Jan 2;151(1):303-12
references.pmid: 18082973
references.citation: Prog Neurobiol. 2002 Oct;68(3):167-207
references.pmid: 12450487
references.citation: J Neurosci. 2001 Jan 15;21(2):477-84
references.pmid: 11160427
references.citation: Ann Neurol. 2003 Mar;53(3):382-9
references.pmid: 12601706
references.citation: J Neurosci. 2006 Sep 6;26(36):9312-22
references.pmid: 16957087
references.citation: J Neurosci. 2007 Oct 3;27(40):10674-84
references.pmid: 17913901
references.citation: J Neurosci. 2004 Aug 4;24(31):6920-7
references.pmid: 15295027
references.citation: Hippocampus. 1991 Oct;1(4):341-54
references.pmid: 1669314
references.citation: J Neurosci. 2006 Nov 29;26(48):12447-55
references.pmid: 17135406
references.citation: J Neurosci. 2002 Apr 1;22(7):2443-50
references.pmid: 11923408
references.citation: Glia. 2001 Jan;33(1):72-86
references.pmid: 11169793
references.citation: J Neurophysiol. 1993 Sep;70(3):961-75
references.pmid: 8229182
references.citation: Glia. 2006 Nov 15;54(7):747-57
references.pmid: 17006903
references.citation: Nature. 1994 Jun 30;369(6483):744-7
references.pmid: 7911978
references.citation: J Neurosci. 2004 Jan 21;24(3):722-32
references.pmid: 14736858
references.citation: J Neurophysiol. 1991 Apr;65(4):771-85
references.pmid: 1675671
references.citation: J Neurosci. 2005 Sep 7;25(36):8131-40
references.pmid: 16148221
references.citation: Nature. 1998 Jan 15;391(6664):281-5
references.pmid: 9440691
references.citation: Nat Cell Biol. 2007 Aug;9(8):945-53
references.pmid: 17618272
references.citation: Science. 1982 May 14;216(4547):745-7
references.pmid: 7079735
references.citation: Neuron. 2008 Apr 24;58(2):168-78
references.pmid: 18439402
references.citation: Exp Physiol. 1990 Mar;75(2):127-62
references.pmid: 2111151