Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, USA.
Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, USA.
Brain Res. 2014 Jan 16;1543:165-72. doi: 10.1016/j.brainres.2013.11.013. Epub 2013 Nov 16.
Early recovery from incomplete spinal cord contusion is improved by prolonged stimulation of the hindbrain's serotonergic nucleus raphe magnus (NRM). Here we examine whether increases in cyclic adenosine monophosphate (cAMP), an intracellular signaling molecule with several known restorative actions on damaged neural tissue, could play a role. Subsequent changes in cAMP-dependent phosphorylation of protein kinase A (PKA) and PKA-dependent phosphorylation of the transcription factor "cAMP response element-binding protein" (CREB) are also analyzed. Rats with moderate weight-drop injury at segment T8 received 2h of NRM stimulation beginning three days after injury, followed immediately by separate extraction of cervical, thoracic and lumbar spinal cord for immunochemical assay. Controls lacked injury, stimulation or both. Injury reduced cAMP levels to under half of normal in all three spinal regions. NRM stimulation completely restored these levels, while producing no significant change in non-injured rats. Pretreatment with the 5-HT7 receptor antagonist pimozide (1 mg/kg, intraperitoneal) lowered cAMP in non-injured rats to injury amounts, which were unchanged by NRM stimulation. The phosphorylated fraction of PKA (pPKA) and CREB (pCREB) was reduced significantly in all three regions after SCI and restored by NRM stimulation, except for pCREB in lumbar segments. In conclusion, SCI produces spreading deficits in cAMP, pPKA and pCREB that are reversible by Gs protein-coupled 5-HT receptors responding to raphe-spinal activity, although these signaling molecules are not reactive to NRM stimulation in normal tissue. These findings can partly explain the benefits of NRM stimulation after SCI.
不完全性脊髓挫伤后早期恢复通过延长后脑的 5-羟色胺能核 Raphe Magnus（NRM）刺激得以改善。在这里，我们研究细胞内信号分子环磷酸腺苷（cAMP）是否可能发挥作用，cAMP 对受损神经组织具有多种已知的修复作用。还分析了 cAMP 依赖性蛋白激酶 A（PKA）磷酸化和 PKA 依赖性转录因子“cAMP 反应元件结合蛋白”（CREB）磷酸化的后续变化。T8 节段接受中度重物坠落损伤的大鼠在损伤后 3 天开始接受 2 小时的 NRM 刺激，随后立即分别提取颈、胸和腰段脊髓进行免疫化学测定。对照鼠缺乏损伤、刺激或两者都没有。损伤使所有三个脊髓区域的 cAMP 水平降至正常水平的一半以下。NRM 刺激完全恢复了这些水平，而对未受伤的大鼠没有产生显著变化。5-HT7 受体拮抗剂匹莫齐德（1mg/kg，腹腔内）预处理使未受伤的大鼠的 cAMP 降低到与损伤量相同的水平，而 NRM 刺激对其没有影响。PKA（pPKA）和 CREB（pCREB）的磷酸化部分在 SCI 后所有三个区域均显著降低，NRM 刺激可恢复，除了腰段的 pCREB。总之，SCI 导致 cAMP、pPKA 和 pCREB 扩散不足，而对 Raphe-spinal 活性有反应的 Gs 蛋白偶联 5-HT 受体可逆转，尽管这些信号分子在正常组织中对 NRM 刺激没有反应。这些发现可以部分解释 NRM 刺激在 SCI 后的益处。
