Calcium regulates the mode of exocytosis induced by hypotonic shock in isolated neuronal presynaptic endings.

Abstract

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.

• Authors: Tatyana V Waseem, Anatoly A Rakovich, Tatyana V Lavrukevich, Sergei V Konev, Sergei V Fedorovich
• Journal: Neurochemistry international (Neurochem Int) Vol. 46 Issue 3 Pg. 235-42 (Feb 2005) ISSN: 0197-0186 [Print] England
• PMID: 15670640 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Chelating Agents
• FM2 10
• Fluorescent Dyes
• Neurotransmitter Agents
• Pyridinium Compounds
• Quaternary Ammonium Compounds
• Aspartic Acid
• Egtazic Acid
• gamma-Aminobutyric Acid
• Acridine Orange
• Calcium

Topics

• Acridine Orange
• Animals
• Aspartic Acid (metabolism)
• Brain Chemistry (drug effects)
• Calcium (physiology)
• Chelating Agents (pharmacology)
• Egtazic Acid (pharmacology)
• Exocytosis (physiology)
• Fluorescent Dyes
• In Vitro Techniques
• Male
• Neurons (metabolism, physiology)
• Neurotransmitter Agents (metabolism)
• Osmotic Pressure
• Presynaptic Terminals (metabolism, physiology)
• Pyridinium Compounds
• Quaternary Ammonium Compounds
• Rats
• Synaptosomes (drug effects, metabolism)
• Water-Electrolyte Imbalance (physiopathology)
• gamma-Aminobutyric Acid (metabolism)