Figure 7.

Interspike calcium current and spontaneous pain. SCI and sham rats were subjected to the CPP paradigm by using a CPP box with three chambers. The white chamber was paired with TTA-P2 (10 mg/kg, i.p.), while the black chamber was paired with vehicle. A, Of the 13 SCI rats tested, seven rats (identified as responders) showed an increase in the difference score of +112 ± 43 s for the drug paired chamber (D-paired, white bar) and a decrease of –142 ± 116 s in the vehicle paired chamber (V-paired, gray bar). Paired t test, *p < 0.05. B, Of the 13 SCI rats tested, six rats (identified as non-responders) showed a decrease of −30 ± 49 s in the D-paired chamber (white bar) and a decrease of −50 ± 108 s in the V-paired chamber (gray bar). C, Sham rats (n = 6) showed an increase of 3 ± 53 s in the D-paired chamber (white bar) and an increase of 9 ± 130 s in the V-paired chamber (gray bar). Data are reported as mean ± SD. D, Comparison of the total interspike Ca²⁺ charge (measured by integrating the total calcium current from −80 to −50 mV) in SCI-nociceptors from responders (165 ± 35 pC/pF, n = 21, res, white bar) versus non-responders (21 ± 3 pC/pF, n = 48, non-res, gray bar). Unpaired t test, *p < 0.05. E, Comparison of the interspike T-type calcium charge in SCI-nociceptors from responders (101 ± 25 pC/pF, n = 24, res, white bar) versus non-responders (17 ± 2 pC/pF, n = 46, non-res, gray bar). Unpaired t test, *p < 0.05.