Effect of extracellular K+ on the intracellular free Ca2+ concentration in leech glial cells and Retzius neurones.
The effects of extracellular K+ on the intracellular free Ca2+ concentration ([Ca2+]i) of neuropile glial cells and Retzius neurones in intact segmental ganglia of the leech Hirudo medicinalis were investigated by using iontophoretically injected fura-2. In both cell types, an elevation of the extracellular K+ concentration ([K+]o) caused an increase in [Ca2+]i, which was blocked by Co2+, Ni2+ and menthol, whereas nicardipine, flunarizine, omega-conotoxin GVIA and omega-agatoxin IVA were ineffective. In Ca(2+)-free solution, the K(+)-induced [Ca2+]i increase was largely suppressed in neuropile glial cells and completely abolished in Retzius neurones. The results indicate that the K(+)-induced [Ca2+]i increase was mainly due to Ca2+ influx through voltage-dependent Ca2+ channels. The Ca2+ channels of the two cell types were activated at different membrane potentials but at the same [K+]o. In both cell types, the recovery from a K(+)-induced [Ca2+]i increase was unaltered in Na(+)-free solution, indicating that active Ca2+ transport across the plasma membrane is mediated by Na(+)-independent mechanisms.
Hochstrate
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Institut für Neurobiologie, Heinrich-Heine-Universität Düsseldorf, Germany.
Piel
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Schlue
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D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D004594:Electrophysiology; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D016257:Fura-2; D017952:Ganglia, Invertebrate / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000502:physiology; D007865:Leeches / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D009457:Neuroglia / Q000187:drug effects / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D011188:Potassium / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology*; D012964:Sodium / Q000378:metabolism
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D012964:Sodium; D011188:Potassium; D002118:Calcium; D016257:Fura-2