Figure 4.

Interspike calcium current at three months postinjury. Interspike currents were measured in SCI-nociceptors and sham-nociceptors isolated at three months postinjury and postlaminectomy, respectively. A, Total interspike calcium current isolated as the current sensitive to replacement of 2 mm Ca²⁺ with 2 mm Co²⁺ in the external solution in SCI-nociceptors (black dots, n = 72) and sham-nociceptors (gray dots, n = 46). Two-way ANOVA followed by Sidak's post hoc comparison, *p < 0.05. B, Total interspike calcium charge measured by integrating the currents shown in A from the afterhyperpolarization of the first action potential (–80 mV) to the time where the voltage reached −50 mV before the second action potential in SCI-nociceptors (black bar, 121.3 ± 17.7 pC/pF, n = 72) and sham-nociceptors (gray bar, 33.7 ± 3.9 pC/pF, n = 46). Unpaired t test, *p < 0.05. C, Correlation between the total interspike calcium charge and the BBB score for the SCI rats (n = 19 rats) shown in panel B. Spearman correlation, p = 0.62, r = −0.123. D, Interspike TTX-sensitive (TTX-sen) sodium current isolated as the current sensitive to 1 μm TTX in SCI-nociceptors (white dots, n = 13). Interspike TTX-resistant (TTX-res) sodium current isolated as the current sensitive to 1 μm A803467 applied on top of 1 μm TTX in SCI-nociceptors (gray dots, n = 13). Interspike Ih current isolated as the current sensitive to 3 mm Cs⁺ in SCI-nociceptors (black dots, n = 12). One-way ANOVA followed by Tukey's post hoc comparison test. Data are reported as mean ± SEM.