Calcium regulates the mode of exocytosis induced by hypotonic shock in isolated neuronal presynaptic endings.
A decrease in the osmolarity of incubation medium is accompanied by calcium influx in neuronal presynaptic endings. We studied the influence of Ca2+ on exocytosis induced by hypotonic shock using the hydrophilic fluorescent dye acridine orange and the hydrophobic fluorescent dye FM2-10. It was shown using acridine orange that lowering of osmolarity to 230 mOsm/l induces exocytosis both in calcium-containing and calcium-free medium. By contrast, we were able to demonstrate calcium-dependence of exocytosis using styryl dye FM2-10. Lowering of osmolarity leads to increase of [3H]D-aspartate and [3H]GABA release in calcium-free medium. Addition of calcium inhibits hypotonic-induced neurotransmitter release. Decreasing of NaCl concentration to 92 mM in isotonic medium is able to induce d-aspartate and GABA release. Thus, our data suggest that hypotonic swelling induces calcium-independent exocytosis possibly by a "kiss and run" mechanism. Calcium influx mediated by stretch channels is able to provoke full fusion between plasma membrane and synaptic vesicles. [3H]D-aspartate and [3H]GABA released by hypotonic shock is determined by sodium lowering rather than by osmolarity decreasing itself.
Waseem
Tatyana V
TV
Institute of Biophysics and Cell Engineering, Akademicheskaya St., 27, Minsk 220072, Belarus.
Rakovich
Anatoly A
AA
Lavrukevich
Tatyana V
TV
Konev
Sergei V
SV
Fedorovich
Sergei V
SV
D000165:Acridine Orange; D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism; D001923:Brain Chemistry / Q000187:drug effects; D002118:Calcium / Q000502:physiology*; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D005089:Exocytosis / Q000502:physiology*; D005456:Fluorescent Dyes; D066298:In Vitro Techniques; D008297:Male; D009474:Neurons / Q000378:metabolism / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000378:metabolism; D009997:Osmotic Pressure; D017729:Presynaptic Terminals / Q000378:metabolism / Q000502:physiology*; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D051381:Rats; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism; D014883:Water-Electrolyte Imbalance / Q000503:physiopathology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D002614:Chelating Agents; C086686:FM2 10; D005456:Fluorescent Dyes; D018377:Neurotransmitter Agents; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D001224:Aspartic Acid; D004533:Egtazic Acid; D005680:gamma-Aminobutyric Acid; D000165:Acridine Orange; D002118:Calcium