Increase in intracellular Ca2+ concentration is not the only cause of lidocaine-induced cell damage in the cultured neurons of Lymnaea stagnalis.

PURPOSE: To determine whether the increase in intracellular Ca2+ concentration induced by lidocaine produces neurotoxicity, we compared morphological changes and Ca2+ concentrations, using fura-2 imaging, in the cultured neurons of Lymnaea stagnalis.

METHODS

We used BAPTA-AM, a Ca2+ chelator, to prevent the increase in the intracellular Ca2+ concentration, and Calcimycin A23187, a Ca2+ ionophore, to identify the relationship between increased intracellular Ca(2+) concentrations and neuronal damage without lidocaine. Morphological changes were confirmed using trypan blue to stain the cells.

RESULTS

Increasing the dose of lidocaine increased the intracellular Ca2+ concentration; however, there was no morphological damage to the cells in lidocaine at 3 x 10(-3) M. Lidocaine at 3 x 10(-2) M increased the intracellular Ca2+ concentration in both saline (from 238 +/- 63 to 1038 +/- 156 nM) and Ca2+-free medium (from 211 +/- 97 to 1046 +/- 169 nM) and produced morphological damage and shrinkage, with the formation of a rugged surface. With the addition of BAPTA-AM, lidocaine at 3 x 10(-2) M moderately increased the intracellular Ca2+ concentration (from 150 +/- 97 to 428 +/- 246 nM) and produced morphological damage. These morphologically changed cells were stained dark blue with trypan blue dye. The Ca2+ ionophore increased the intracellular Ca2+ concentration (from 277 +/- 191 to 1323 +/- 67 nM) and decreased it to 186 +/- 109 nM at 60 min. Morphological damage was not observed during the 60 min, but became apparent a few hours later.

CONCLUSION

These results indicated that the increase in intracellular Ca2+ concentration is not the only cause of lidocaine-induced cell damage.