Perturbation of Ca²⁺ stores and store-operated Ca²⁺ influx by lidocaine in neuronal N2A and NG108-15 cells

In this report we examined the effects of lidocaine on Ca²⁺ homeostasis of neuronal cells using microfluorimetric measurement of cytosolic Ca²⁺ with fura 2 as probe. In mouse neuroblastoma N2A cells, 10 mM lidocaine caused Ca²⁺ release from the cyclopiazonic acid (CPA)-dischargeable pool and abolished ATP-triggered Ca²⁺ release. Lidocaine-triggered Ca²⁺ release was not affected by xestospongin C (XeC), an inositol 1,4,5-trisphosphate receptor (IP3R) inhibitor. N2A cells did not have functional ryanodine receptors (RYR) (absence of caffeine response) and we used differentiated NG108-15 cells (presence of caffeine response) for further experiments. Caffeine-triggered Ca²⁺ release was unaffected by a brief lidocaine exposure, but was eliminated after a prolonged treatment of lidocaine, suggesting lidocaine abolished caffeine action possibly not by interfering caffeine binding but via Ca²⁺ store depletion. Lidocaine-elicited Ca²⁺ release was unaffected by XeC or a high concentration of ryanodine, suggesting Ca²⁺ release was not via IP3R or RYR. Lidocaine did not affect nigericin-dischargeable lysosomal Ca²⁺ stores. Lastly, we observed that lidocaine suppressed CPA-induced store-operated Ca²⁺ influx in both N2A cells and differentiated NG108-15 cells. Our results suggest two novel actions of lidocaine in neuronal cells, namely, depletion of Ca²⁺ store (via an IP3R- and RYR-independent manner) and suppression of store-operated Ca²⁺ influx.