Fig. 1. Effect of lidocaine on neuronal Ca2+cyt: Representative single neuron Ca2+cyttracings. The asterisk indicates plasma membrane lysis and necrotic cell death for the indicated neuron after exposure to 5% lidocaine, after which Ca2+cytvalues are not meaningful because the cytoplasm is in direct communication with extracellular buffer. Note: two-fold expansion of y-axis for each successive graph at lower lidocaine concentrations. Neurons selected for the 5 and 2.5% lidocaine plots represent the lower end of Ca2+cytvalues observed for these concentrations, to more clearly illustrate the initial small peak in Ca2+cyt(cf. figs. 3 and 4). The Tris control illustrated was equimolar to 5% lidocaine HCl (i.e. , 185 mm). Tris controls for less than 5% lidocaine are omitted for clarity; all were similar to the Tris control illustrated for 5% lidocaine;i.e. , flat with minimal increase. Tracings are representative of N = 5 to 6 experiments for 1.0–5.0% lidocaine; and of N = 3 to 4 experiments for 0.1–0.5% lidocaine and for all Tris controls; number of neurons per experiment = 17 ± 5 (SD).