Objective: To investigate the rebound depolarization of substantia gelatinosa (SG) neurons in rat spinal dorsal horn and explore its modulatory mechanisms to provide better insights into rebound depolarization-related diseases.
Methods: Parasagittal slices of the spinal cord were prepared from 3- to 5-week-old Sprague-Dawley rats. The electrophysiologic characteristics and responses to hyperpolarization stimulation were recorded using whole-cell patch-clamp technique. The effects of hyperpolarization-activated cyclic nucleotide gated cation (HCN) channel blockers and T-type calcium channel blockers on rebound depolarization of the neurons were studied.
Results: A total of 63 SG neurons were recorded. Among them, 23 neurons showed no rebound depolarization, 19 neurons showed rebound depolarization without spikes, and 21 neurons showed rebound depolarization with spikes. The action potential thresholds of the neurons without rebound depolarization were significantly higher than those of the neurons with rebound depolarization and spikes (-28.7∓1.6 mV vs -36.0∓2.0 mV, P<0.05). The two HCN channel blockers CsCl and ZD7288 significantly delayed the latency of rebound depolarization with spike from 45.9∓11.6 ms to 121.6∓51.3 ms (P<0.05) and from 36.2∓10.3 ms to 73.6∓13.6 ms (P<0.05), respectively. ZD7288 also significantly prolonged the latency of rebound depolarization without spike from 71.9∓35.1 ms to 267.0∓68.8 ms (P<0.05). The T-type calcium channel blockers NiCl2 and mibefradil strongly decreased the amplitude of rebound depolarization with spike from 19.9∓6.3 mV to 9.5∓4.5 mV (P<0.05) and from 26.1∓9.4 mV to 15.5∓5.0 mV (P<0.05), respectively. Mibefradil also significantly decreased the amplitude of rebound depolarization without spike from 14.3∓3.0 mV to 7.9∓2.0 mV (P<0.05).
Conclusion: Nearly two-thirds of the SG neurons have rebound depolarizations modulated by HCN channel and T-type calcium channel.
目的: 研究大鼠脊髓背角胶状质（SG）神经元的去极化反跳及调控机制，以期对去极化反跳相关疾病的临床治疗提供参考。
方法: 选取3~5周龄SD大鼠，制作离体脊髓纵切片，应用全细胞膜片钳技术记录SG神经元的电生理学特点及接受超极化刺激后的反应，并观察超极化激活环核苷酸门控阳离子（HCN）通道阻断剂和T型钙（Cav3）通道阻断剂对去极化反跳的作用。
结果: 共记录了63个SG神经元的电活动，其中23个无去极化反跳，19个为去极化反跳无放电，21个为去极化反跳伴放电。无去极化反跳组SG神经元的动作电位阈值（-28.7±1.6 mV）明显高于去极化反跳伴放电组（-36.0±2.0 mV）（P＜0.05）。HCN通道阻断剂氯化铯和ZD7288 可显著延长去极化反跳伴放电的潜伏期，分别从45.9±11.6 ms增加到121.6±51.3 ms（P＜0.05）和从36.2±10.3 ms 增加到73.6±13.6 ms（P＜0.05）；ZD7288 也能显著延长去极化反跳不伴放电的潜伏期，从71.9±35.1 ms 增加到267.0±68.8 ms（P＜0.05），而T型钙通道阻断剂氯化镍和米贝地尔可显著降低去极化反跳伴放电的振幅，分别从19.9±6.3 mV降到9.5±4.5 mV（P＜0.05）和从26.1±9.4 mV降到15.5±5.0 mV（P＜0.05），米贝地尔同样能显著降低去极化反跳不伴放电的振幅，从14.3±3.0 mV降低至7.9±2.0 mV（P＜0.05）。
结论: 近2/3的SG神经元有去极化反跳，其潜伏期和振幅分别受HCN通道和T型钙通道调控。