Potassium-depolarization-induced cytoplasmic [Ca2+] transient in freshly dissociated pyramidal neurones of the rat dorsal cochlear nucleus.
The significance of voltage-activated Ca2+ currents in eliciting cytoplasmic Ca2+ transients was studied in pyramidal neurones isolated from the rat dorsal cochlear nucleus using combined enzyme treatment/mechanical trituration. Increases in cytoplasmic Ca2+ concentration ([Ca2+]i) were evoked by K+-induced depolarizations (10-50 mM) and monitored by the Fura-2 fluorimetric technique. The acutely dissociated neurones had a resting [Ca2+]i of 17.2+/-0.5 nM. They possessed caffeine-sensitive Ca2+ stores which were empty at rest; these stores could be filled with Ca2+ entering from the extracellular space and were re-emptied quickly. The effects of various specific high-voltage-activated (HVA) Ca2+ channel antagonists (nifedipine, omega-agatoxin IVA and omega-conotoxin GVIA) on [Ca2+]i transients were tested. Analysis of the blocking effects of these agents on the [Ca2+]i, transients indicates that, in the pyramidal neurones of the dorsal cochlear nucleus, N-type Ca2+ channels are primarily responsible for producing the depolarization-induced increases in [Ca2+]i.
Rusznák
Z
Z
Department of Physiology, University of Debrecen, Medical and Health Science Centre, Medical School, Hungary.
Harasztosi
C
C
Stanfield
P R
PR
Kovács
L
L
Szûcs
G
G
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020864:Calcium Channels, N-Type / Q000378:metabolism*; D017626:Cochlear Nucleus / Q000166:cytology*; D003593:Cytoplasm / Q000378:metabolism; D005456:Fluorescent Dyes; D016257:Fura-2; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009543:Nifedipine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology*; D017966:Pyramidal Cells / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D013268:Stimulation, Chemical; D013779:Tetrodotoxin / Q000494:pharmacology; D020867:omega-Agatoxin IVA / Q000494:pharmacology; D020866:omega-Conotoxin GVIA / Q000494:pharmacology
D002121:Calcium Channel Blockers; D020864:Calcium Channels, N-Type; D005456:Fluorescent Dyes; D020867:omega-Agatoxin IVA; D013779:Tetrodotoxin; D020866:omega-Conotoxin GVIA; D009543:Nifedipine; D011188:Potassium; D002118:Calcium; D016257:Fura-2