Na(+)-Ca2+ exchange in rat dorsal root ganglion neurons.
The role of the Na(+)-Ca2+ exchanger was examined in isolated rat dorsal root ganglion (DRG) neurons. Neurons were dialyzed with the Ca2+ indicator Indo-1. Ca2+ transients were elicited by depolarizing the cells from -80 to 0 mV for 100 ms under voltage clamp conditions. In most cells (45 of 67), the decay of intracellular Ca2+ concentration ([Ca2+]i) could be fitted with a single exponential with a time constant of 2.43 s. In the remaining 22 cells, the decay of [Ca2+]i could be described with a double exponential with time constants of 0.76 and 11.84 s. In cells that displayed a biphasic [Ca2+]i relaxation, Na(+)-free medium caused resting [Ca2+]i to increase from 116 to 186 nM; the slow component of recovery to basal [Ca2+]i was nearly abolished in Na(+)-free medium or by application of 5 mM Ni2+. In 35 of 45 cells displaying a monophasic [Ca2+]i decay, omitting external Na+ increased the time constant of [Ca2+]i decay from 2.02 to 3.63 s. In the remaining 10 cells, Na(+)-free solution did not affect Ca2+ handling. The time constant of [Ca2+]i relaxation was voltage dependent. These findings demonstrate the important role of the Na(+)-Ca2+ exchanger in DRG neurons. Its presence was further confirmed both at the mRNA and the protein level.
Verdru
P
P
Laboratorium voor Fysiologie, Katholieke Universiteit Leuven, Belgium.
De Greef
C
C
Mertens
L
L
Carmeliet
E
E
Callewaert
G
G
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004594:Electrophysiology; D005727:Ganglia, Spinal / Q000166:cytology / Q000378:metabolism*; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D009474:Neurons / Q000378:metabolism*; D009532:Nickel / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D051381:Rats; D012964:Sodium / Q000378:metabolism / Q000502:physiology; D019831:Sodium-Calcium Exchanger
D002352:Carrier Proteins; D019831:Sodium-Calcium Exchanger; D009532:Nickel; D012964:Sodium; D002118:Calcium