A role of intracellular Na+ in the regulation of synaptic transmission and turnover of the vesicular pool in cultured hippocampal cells.
Propagation of action potentials in axons and dendrites increases intracellular Na+ ([Na+]i) and Ca2+ concentrations ([Ca2+]i). While the importance of [Ca2+]i in synaptic transmission is well established, a possible functional role of [Na+]i is unclear. In cultured hippocampal cells, [Na+]i was increased by veratridine. We have then measured spontaneous excitatory postsynaptic currents (sEPSCs) and, by means of fluorescent dyes, changes in [Na+]i, in [Ca2+]i, and in the turnover of the vesicular pool of individual boutons. An elevation of [Na+]i and a concomitant rise in [Ca2+]i, led to a large increase in sEPSC frequency and in the turnover of the presynaptic vesicular pool. Extracellular Ca2+ was essential for these effects of elevated [Na+]i on synaptic transmission. They probably occur via Na+/Ca2+ exchange.
Bouron
A
A
Department of Pharmacology, University of Bern, Switzerland.
Reuter
H
H
D000818:Animals; D001692:Biological Transport / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured / Q000187:drug effects / Q000502:physiology; D003712:Dendrites / Q000502:physiology; D004594:Electrophysiology; D005089:Exocytosis / Q000502:physiology; D005456:Fluorescent Dyes; D006624:Hippocampus / Q000166:cytology*; D008564:Membrane Potentials / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000502:physiology / Q000648:ultrastructure; D017729:Presynaptic Terminals / Q000502:physiology; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000378:metabolism*; D009435:Synaptic Transmission / Q000502:physiology*; D013572:Synaptic Vesicles / Q000502:physiology*; D014701:Veratridine / Q000494:pharmacology
C073804:FM1 43; D005456:Fluorescent Dyes; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D014701:Veratridine; D012964:Sodium; D002118:Calcium