Effects of tetracaine and lidocaine on intracellular Zn2+ levels in rat neurons : Preliminary analysis with FluoZin-3 fluorescence

There are some differences in cytotoxic actions between local anesthetics. In a study performed using rat thymocytes, lidocaine increased intracellular Zn2+ concentration whereas tetracaine decreased it. However, thymocytes are not subject to local anesthetics. This study was conducted to confirm the actions of tetracaine and lidocaine on neurons. Tetracaine and lidocaine changed intracellular Zn2+ levels in rat cerebellar granule neurons, as had been observed in rat thymocytes. The changes in intracellular Zn2+ levels by these local anesthetics were statistically significant, but small. The mechanism of lidocaine-induced increase in intracellular Zn2+ levels in neurons was similar to that in rat thymocytes. The mechanism of tetracaine-induced decrease in intracellular Zn2+ levels in neurons did not seem to be consistent with that in rat thymocytes. Further studies will be needed to see if the changes in intracellular Zn2+ levels by local anesthetics correspond to differences in cytotoxic activities since their actions on intracellular Zn2+ levels of neurons were weak.