Figure 3. Ca²⁺ transient parameters associated with evoked NCX activity.

A, high K⁺ (30 mm, 4 s) evoked Ca²⁺ transients from an IB4+ (continuous trace) and an IB4– (dashed trace) cutaneous DRG neuron, in which a concentration of 325 nm Ca²⁺ is indicated to provide a benchmark to evaluate the amplitude–duration relationship. B, pooled transient amplitude–duration (time elapsed at or above a level [Ca²⁺]_i) data for the 2 s-responders and 2 s-non-responders analysed in Fig.2E and F, where transient duration data before and after Li⁺ application are plotted. The evoked transient for each neuron was analysed as a function of the duration at which the transient was at or above concentrations ranging from 275 to 400 nm using increments of 25 nm Ca²⁺. C, data for the 2 s-non-responders in B (in response to the 2 s high K⁺ application) are replotted along with the average amplitude–duration data for these neurons in response to the 4 s high K⁺ application (4 s High K⁺), before (Na⁺) and after (Li⁺) NCX block. D, evoked NCX activity was detected in a third subset of neurons in which application if Li⁺ resulted in an increase in resting [Ca²⁺]_i (arrow). Inset: evoked Ca²⁺ transients before (dashed line) and after (continuous line) NCX block. E, pooled data demonstrating the significant shift increase in resting [Ca²⁺]_i with application of Li⁺ in a subset of neurons (Li⁺ Recruited, P < 0.01, n = 8) in which evoked NCX activity was subsequently detected. F, pooled amplitude–duration data for the subset of neurons in which the Li^+-induced increase in resting [Ca²⁺]_i resulted in the recruitment of evoked NCX activity.