title: Mitochondrial transport in processes of cortical neurons is independent of intracellular calcium.
abstract: Mitochondria show extensive movement along neuronal processes, but the mechanisms and function of this movement are not clearly understood. We have used high-resolution confocal microscopy to simultaneously monitor movement of mitochondria and changes in intracellular [Ca(2+)] ([Ca(2+)](i)) in rat cortical neurons. A significant percentage (27%) of the total mitochondria in cortical neuronal processes showed movement over distances of >2 microM. The average velocity was 0.52 microm/s. The velocity, direction, and pattern of mitochondrial movement were not affected by transient increases in [Ca(2+)](i) associated with spontaneous firing of action potentials. Stimulation of Ca(2+) transients with forskolin (10 microM) or bicuculline (10 microM), or sustained elevations of [Ca(2+)](i) evoked by glutamate (10 microM) also had no effect on mitochondrial transit. Neither removal of extracellular Ca(2+), depletion of intracellular Ca(2+) stores with thapsigargin, or inhibition of synaptic activity with TTX (1 microM) or a cocktail of CNQX (10 microM) and MK801 (10 microM) affected mitochondrial movement. These results indicate that movement of mitochondria along processes is a fundamental activity in neurons that occurs independently of physiological changes in [Ca(2+)](i) associated with action potential firing, synaptic activity, or release of Ca(2+) from intracellular stores.
authors.affiliation: Department of Neurology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California, USA.
authors.forename: Luis
authors.initials: L
authors.lastname: Beltran-Parrazal
authors.forename: Héctor E
authors.initials: HE
authors.lastname: López-Valdés
authors.forename: K C
authors.initials: KC
authors.lastname: Brennan
authors.forename: Mauricio
authors.initials: M
authors.lastname: Díaz-Muñoz
authors.forename: Jean
authors.initials: J
authors.lastname: de Vellis
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Charles
mesh_terms: D000447:Aldehydes / Q000378:metabolism; D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D001692:Biological Transport / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology*; D005576:Colforsin / Q000378:metabolism; D005260:Female; D018756:GABA Antagonists / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D007091:Image Processing, Computer-Assisted; D008928:Mitochondria / Q000378:metabolism* / Q000648:ultrastructure; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000447:Aldehydes; D018756:GABA Antagonists; C111472:mitotracker green FM; D005576:Colforsin; D018698:Glutamic Acid; D002118:Calcium; D001640:Bicuculline