title: To Break or to Brake Neuronal Network Accelerated by Ammonium Ions?
abstract: OBJECTIVE
  The aim of present study was to investigate the effects of ammonium ions on in vitro neuronal network activity and to search alternative methods of acute ammonia neurotoxicity prevention.
  
  
  METHODS
  Rat hippocampal neuronal and astrocytes co-cultures in vitro, fluorescent microscopy and perforated patch clamp were used to monitor the changes in intracellular Ca2+- and membrane potential produced by ammonium ions and various modulators in the cells implicated in neural networks.
  
  
  RESULTS
  Low concentrations of NH4Cl (0.1-4 mM) produce short temporal effects on network activity. Application of 5-8 mM NH4Cl: invariably transforms diverse network firing regimen to identical burst patterns, characterized by substantial neuronal membrane depolarization at plateau phase of potential and high-amplitude Ca2+-oscillations; raises frequency and average for period of oscillations Ca2+-level in all cells implicated in network; results in the appearance of group of «run out» cells with high intracellular Ca2+ and steadily diminished amplitudes of oscillations; increases astrocyte Ca2+-signalling, characterized by the appearance of groups of cells with increased intracellular Ca2+-level and/or chaotic Ca2+-oscillations. Accelerated network activity may be suppressed by the blockade of NMDA or AMPA/kainate-receptors or by overactivation of AMPA/kainite-receptors. Ammonia still activate neuronal firing in the presence of GABA(A) receptors antagonist bicuculline, indicating that «disinhibition phenomenon» is not implicated in the mechanisms of networks acceleration. Network activity may also be slowed down by glycine, agonists of metabotropic inhibitory receptors, betaine, L-carnitine, L-arginine, etc.
  
  
  CONCLUSIONS
  Obtained results demonstrate that ammonium ions accelerate neuronal networks firing, implicating ionotropic glutamate receptors, having preserved the activities of group of inhibitory ionotropic and metabotropic receptors. This may mean, that ammonia neurotoxicity might be prevented by the activation of various inhibitory receptors (i.e. by the reinforcement of negative feedback control), instead of application of various enzyme inhibitors and receptor antagonists (breaking of neural, metabolic and signaling systems).
authors.affiliation: Laboratory of intracellular signaling, Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Russia; Laboratory of bioenergetics, Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Russia.
authors.forename: Vladimir V
authors.initials: VV
authors.lastname: Dynnik
authors.affiliation: Laboratory of intracellular signaling, Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Russia.
authors.forename: Alexey V
authors.initials: AV
authors.lastname: Kononov
authors.affiliation: Laboratory of intracellular signaling, Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Russia.
authors.forename: Alexander I
authors.initials: AI
authors.lastname: Sergeev
authors.affiliation: Laboratory of intracellular signaling, Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Russia.
authors.forename: Iliya Y
authors.initials: IY
authors.lastname: Teplov
authors.affiliation: Laboratory of intracellular signaling, Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Russia.
authors.forename: Arina V
authors.initials: AV
authors.lastname: Tankanag
authors.affiliation: Laboratory of intracellular signaling, Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Russia.
authors.forename: Valery P
authors.initials: VP
authors.lastname: Zinchenko
mesh_terms: D000643:Ammonium Chloride / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D009415:Nerve Net / Q000187:drug effects*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000378:metabolism; D018092:Kainic Acid Receptors / Q000378:metabolism
chemical_list: D000643:Ammonium Chloride; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors