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


CONCLUSIONS
These results indicated that the increase in intracellular Ca2+ concentration is not the only cause of lidocaine-induced cell damage.
Kasaba
Toshiharu
T
Department of Anesthesiology and Intensive Care, Faculty of Medicine, University of Miyazaki, Kiyotake-Cho, Miyazaki 889-1692, Japan.
Onizuka
Shin
S
Kashiwada
Masatoshi
M
Takasaki
Mayumi
M
D000779:Anesthetics, Local / Q000633:toxicity*; D000818:Animals; D000001:Calcimycin / Q000008:administration & dosage; D002118:Calcium / Q000378:metabolism*; D018929:Cell Culture Techniques / Q000379:methods; D002614:Chelating Agents / Q000008:administration & dosage; D004396:Coloring Agents; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000008:administration & dosage / Q000031:analogs & derivatives; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism; D017136:Ion Transport / Q000187:drug effects; D007476:Ionophores / Q000008:administration & dosage; D008012:Lidocaine / Q000633:toxicity*; D008195:Lymnaea; D009474:Neurons / Q000187:drug effects*; D020258:Neurotoxicity Syndromes / Q000209:etiology*; D013997:Time Factors; D014343:Trypan Blue
D000779:Anesthetics, Local; D002614:Chelating Agents; D004396:Coloring Agents; D007476:Ionophores; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D000001:Calcimycin; D004533:Egtazic Acid; D008012:Lidocaine; D014343:Trypan Blue; D002118:Calcium