title: Sodium-calcium exchanger and R-type Ca(2+) channels mediate spontaneous [Ca(2+)]i oscillations in magnocellular neurones of the rat supraoptic nucleus.
abstract: Isolated supraoptic neurones generate spontaneous [Ca(2+)]i oscillations in isolated conditions. Here we report in depth analysis of the contribution of plasmalemmal ion channels (Ca(2+), Na(+)), Na(+)/Ca(2+) exchanger (NCX), intracellular Ca(2+) release channels (InsP3Rs and RyRs), Ca(2+) storage organelles, plasma membrane Ca(2+) pump and intracellular signal transduction cascades into spontaneous Ca(2+) activity. While removal of extracellular Ca(2+) or incubation with non-specific voltage-gated Ca(2+) channel (VGCC) blocker Cd(2+) suppressed the oscillations, neither Ni(2+) nor TTA-P2, the T-type VGCC blockers, had an effect. Inhibitors of VGCC nicardipine, ω-conotoxin GVIA, ω-conotoxin MVIIC, ω-agatoxin IVA (for L-, N-, P and P/Q-type channels, respectively) did not affect [Ca(2+)]i oscillations. In contrast, a specific R-type VGCC blocker SNX-482 attenuated [Ca(2+)]i oscillations. Incubation with TTX had no effect, whereas removal of the extracellular Na(+) or application of an inhibitor of the reverse operation mode of Na(+)/Ca(2+) exchanger KB-R7943 blocked the oscillations. The mitochondrial uncoupler CCCP irreversibly blocked spontaneous [Ca(2+)]i activity. Exposure of neurones to Ca(2+) mobilisers (thapsigargin, cyclopiazonic acid, caffeine and ryanodine); 4-aminopyridine (A-type K(+) current blocker); phospholipase C and adenylyl cyclase pathways blockers U-73122, Rp-cAMP, SQ-22536 and H-89 had no effect. Oscillations were blocked by GABA, but not by glutamate, apamin or dynorphin. In conclusion, spontaneous oscillations in magnocellular neurones are mediated by a concerted action of R-type Ca(2+) channels and the NCX fluctuating between forward and reverse modes.
authors.affiliation: Department of Molecular Neurophysiology, Institute of Experimental Medicine, Czech Academy of Sciences, Videnska 1083, 14220 Prague, Czech Republic; Institute of Physiology, Czech Academy of Sciences, Videnska 1083, 14220 Prague, Czech Republic; Institute of Biophysics and Informatics, First Medical Faculty, Charles University in Prague, Salmovska 1, 12000 Prague, Czech Republic.
authors.forename: Stepan
authors.initials: S
authors.lastname: Kortus
authors.affiliation: Department of Molecular Neurophysiology, Institute of Experimental Medicine, Czech Academy of Sciences, Videnska 1083, 14220 Prague, Czech Republic.
authors.forename: Chinnapaiyan
authors.initials: C
authors.lastname: Srinivasan
authors.affiliation: Department of Molecular Neurophysiology, Institute of Experimental Medicine, Czech Academy of Sciences, Videnska 1083, 14220 Prague, Czech Republic; Department of Neuroscience, Charles University, Second Medical Faculty, V Uvalu 84, 15006 Prague, Czech Republic.
authors.forename: Oksana
authors.initials: O
authors.lastname: Forostyak
authors.affiliation: Institute of Physiology, Czech Academy of Sciences, Videnska 1083, 14220 Prague, Czech Republic; Institute of Biophysics and Informatics, First Medical Faculty, Charles University in Prague, Salmovska 1, 12000 Prague, Czech Republic.
authors.forename: Martin
authors.initials: M
authors.lastname: Zapotocky
authors.affiliation: Department of Physiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Ueta
authors.affiliation: Department of Neuroscience, Charles University, Second Medical Faculty, V Uvalu 84, 15006 Prague, Czech Republic; Department of Neuroscience, Institute of Experimental Medicine, Czech Academy of Sciences, Videnska 1083, 14220 Prague, Czech Republic.
authors.forename: Eva
authors.initials: E
authors.lastname: Sykova
authors.affiliation: Department of Neuroscience, Charles University, Second Medical Faculty, V Uvalu 84, 15006 Prague, Czech Republic; Department of Cellular Neurophysiology, Institute of Experimental Medicine, Czech Academy of Sciences, Videnska 1083, 14220 Prague, Czech Republic.
authors.forename: Alexandr
authors.initials: A
authors.lastname: Chvatal
authors.affiliation: University of Manchester, School of Biological Sciences, D.4417 Michael Smith Building, Oxford Road, M13 9PT Manchester, United Kingdom; Achucarro Center for Neuroscience, IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain; Department of Neurosciences, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain; University of Nizhny Novgorod, Nizhny Novgorod 603022, Russia. Electronic address: Alexej.Verkhratsky@manchester.ac.uk.
authors.forename: Alexei
authors.initials: A
authors.lastname: Verkhratsky
authors.affiliation: Department of Molecular Neurophysiology, Institute of Experimental Medicine, Czech Academy of Sciences, Videnska 1083, 14220 Prague, Czech Republic; Institut National de la Santé et de la Recherche Médicale, Unité de recherche U1198, Université Montpellier, 34095 Montpellier, France; Ecole Practique des Hautes Etudes, Sorbonne, 75014 Paris, France. Electronic address: gdaya@univ-montp2.fr.
authors.forename: Govindan
authors.initials: G
authors.lastname: Dayanithi
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D020908:Calcium Channels, R-Type / Q000378:metabolism*; D020013:Calcium Signaling; D042541:Intracellular Space / Q000378:metabolism; D015640:Ion Channel Gating; D008297:Male; D009474:Neurons / Q000378:metabolism*; D018377:Neurotransmitter Agents / Q000378:metabolism; D015221:Potassium Channels / Q000378:metabolism; D017208:Rats, Wistar; D015290:Second Messenger Systems; D012964:Sodium / Q000378:metabolism; D015222:Sodium Channels / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000378:metabolism*; D013495:Supraoptic Nucleus / Q000378:metabolism*; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D020908:Calcium Channels, R-Type; D018377:Neurotransmitter Agents; D015221:Potassium Channels; D015222:Sodium Channels; D019831:Sodium-Calcium Exchanger; D012964:Sodium; D010738:Type C Phospholipases; D000262:Adenylyl Cyclases; D002118:Calcium
keywords: 1,4,5-Trisphosphate; Ca(2+) channel toxins; Ca(2+) clearance; Ca(2+) homeostasis; Ca(2+) imaging; Ca(2+) oscillations; Ca(2+) signalling; GABA; Glutamate; Hypothalamus; Mitochondria; Na(+)/Ca(2+) exchanger; Oxytocin; Plasma membrane calcium pump; Sarcoendoplasmic reticulum Ca(2+)-ATPase; Supraoptic nucleus; Tetrodotoxin; Transgenic rats; Vasopressin; Voltage-gated Ca(2+) channels