Fig. 5. Effect of thapsigargin pretreatment: representative single neuron Ca2+cyttracings. LA was added exactly at time 0. Thapsigargin 100 nm pretreatment is indicated approximately by the arrow, with slight variations in time relative to LA addition between experiments. Ca2+cytvalues as graphed are normalized to the baseline value in the 5 min preceding LA addition (i.e. , after thapsigargin addition). Note: two y-axes for different magnitudes of Ca2+cytresponse between (A ) and (B ), and two types of Ca2+cytresponse (rapid, high and slow, low) to 2.5% lidocaine. The rapid, high Ca2+cytresponse to 2.5% lidocaine (A ) occurred in 4 out of 65 neurons in three experiments. The slow, low Ca2+cytresponse to 2.5% lidocaine (B ) occurred in the other 61 neurons. The other tracings were selected from 3 to 4 experiments with greater than 50 neurons total for each LA concentration. Neuronal death occurred before 60 min for all neurons treated with 5% lidocaine, and for the neurons treated with 2.5% lidocaine which had a rapid, high calcium response. In the individual neuron tracings presented, the tracing stops at the time of neuronal death. Lidocaine 1% (59 neurons in 3 experiments) and bupivacaine 0.25% (61 neurons in 3 experiments) had the same pattern as shown for 0.625% bupivacaine and Tris control;i.e. , little change in Ca2+cytafter LA addition, and are omitted for clarity. LA concentrations equipotent to lidocaine less than 1% were not tested.
