The Journal of Neurophysiology Vol. 77 No. 1 January 1997, pp. 484-490
Copyright ©1997 The American Physiological Society

Na⁺-Ca²⁺ Exchange in Rat Dorsal Root Ganglion Neurons

P. Verdru, C. De Greef, L. Mertens, E. Carmeliet, and G. Callewaert

Laboratorium voor Fysiologie, Katholieke Universiteit Leuven, Campus Gasthuisberg, B-3000 Leuven, Belgium

Verdru, P., C. De Greef, L. Mertens, E. Carmeliet, and G. Callewaert. Na⁺-Ca²⁺ exchange in rat dorsal root ganglion neurons. J. Neurophysiol. 77: 484-490, 1997. 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.

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