Resting potential of rat cerebellar granule cells during early maturation in vitro.
The survival of rat cerebellar granule cells maintained in vitro is enhanced by a KCl-enriched medium. This effect is classically interpreted as resulting from a higher cytosolic calcium concentration. This implies the presence of voltage-dependent Ca2+ channels and a membrane potential that can respond to changes in external K+. Since previous studies cast a doubt on these two conditions, we reinvestigated the resting membrane potential and Ca2+ influxes in rat cerebellar granule neurones during the first week in vitro using a fluorescence imaging approach. Membrane potential was assessed with the fluorescent dye bis-oxonol, and intracellular free calcium with Fura-2. Resting potential was shown to progressively decrease from -40 mV at the first day in vitro to -60 mV at day 7. At all times in culture, as early as day 0, cells were depolarized when external KCl concentration was increased from 5 to 30 mM. This depolarization resulted in an increased cytosolic calcium concentration due to Ca2+ influx through L-type and N-type voltage-activated Ca2+ channels, functional at day 0. Gross estimations of the permeabilities of Na+ and Cl- were obtained at various times in culture by measuring the changes in resting potential brought about by a reduction of their external concentration. A progressive increase of the relative permeability to K+ ions seems to underlie the evolution of the resting potential with time.
Becherer
U
U
Laboratoire de Neurobiologie Cellulaire (UPR 9009 CNRS), Strasbourg, France.
Rodeau
J L
JL
Feltz
A
A
D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000502:physiology; D002478:Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D002531:Cerebellum / Q000166:cytology*; D002712:Chlorides / Q000378:metabolism; D005456:Fluorescent Dyes; D015640:Ion Channel Gating / Q000502:physiology; D008564:Membrane Potentials / Q000502:physiology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000378:metabolism; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D013858:Thiobarbiturates
D015220:Calcium Channels; D002712:Chlorides; D005456:Fluorescent Dyes; D013757:Tetraethylammonium Compounds; D013858:Thiobarbiturates; C025284:bis(1,3-diethylthiobarbiturate)trimethineoxonol; D019789:Tetraethylammonium; D011189:Potassium Chloride; D012964:Sodium; D011188:Potassium; D002118:Calcium