Na+-Ca2+ Exchange in Rat Dorsal Root Ganglion Neurons. Verdru, P., C. De Greef, L. Mertens, E. Carmeliet and G. Callewaert. From.
APStracts 3:0177N, 1996.
SUMMARY AND CONCLUSIONS
1. 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. 2. In most cells (45 out 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. 3. 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 out 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. 4. The time constant of [Ca2+]i relaxation was voltage dependent. 5. 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.

Received 2 April 1996; accepted in final form 31 July 1996.
APS Manuscript Number J271-6.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 19 September 1996