Axon Regenration: Synergistic Actions of the MAPK and Cyclic AMP Pathways

描述（由申请人提供）：我们的最终目标是制定有效的策略来改善人类脊髓损伤（SCI）后的预后。我们已经证明（Pearse et al., 2004）， SC植入物，一次性向植入物上方和下方的脊髓注射cAMP，以及为期两周的罗利普兰皮下注射的三重组合，诱导了5 -羟色胺能纤维大量生长到植入物内部，并进入植入物尾部的脊髓。在尾索中血清素能轴突生长最好的组中观察到运动测试成绩的显著改善。在这些结果的基础上，我们提出了使用相同损伤模型和SC移植的三个特定目标（Pearse et al., 2004）。在Aim 1中，我们将确定cAMP升高的最有效递送部位（病变、中缝体或两者）（通过测量纤维和评估运动）。已知BDNF也促进5 -羟色胺能轴突生长到SC移植物的脊髓尾端；因此，我们将使用相同的SCI模式确定BDNF最有效的输送部位。在目的2中，我们建议测试cAMP升高和BDNF联合使用比单独使用更有效的可能性。将cAMP（最佳途径）和BDNF（最佳途径）联合使用，并将血清素能轴突生长反应与单独使用任一因素进行比较。行为测试结果将与每只动物的轴突生长相关联。在目标3中，我们建议在我们最有效的治疗后确定血清素能投射的功能。首先，药物阻断血清素能受体引起的运动变化将被评估。其次，我们将确定在电刺激raphespinal通路后对躯体传入刺激的反射反应。第三，验证最佳处理后下行纤维释放5-HT的情况。探索联合疗法以改善损伤部位以外的血清素能纤维生长，并确定潜在的改善生长对运动的作用，将在未来带来新的临床策略。

DESCRIPTION (provided by applicant): Our ultimate goal is to develop effective strategies to improve outcome after human spinal cord injury (SCI). We have demonstrated (Pearse et al., 2004) that a triple combination of a SC implant, a one-time injection of cAMP into the cord above and below the implant, and a two-week subcutaneous infusion of Rolipram induced substantial growth of serotonergic fibers into the implant and beyond into the cord caudal to the implant. A marked improvement in locomotor test scores was observed in groups with the best growth of serotonergic axons in the caudal cord. To build on these results, we propose three Specific Aims using the same injury model and SC grafting (Pearse et al., 2004). In Aim 1, we will determine the most effective delivery site (lesion, raphe somata, or both) for cAMP elevation (by measuring fibers and evaluating locomotion). BDNF is known also to promote growth of serotonergic axons into the cord caudal to a SC graft; therefore we will determine the most efficacious site for BDNF delivery using the same SCI paradigm. In Aim 2, we propose to test the possibility that the combination of cAMP elevation and BDNF administration will be more effective than either one alone. Administration of cAMP (best route) and BDNF (best route) will be combined and the serotonergic axon growth response compared to that observed with either factor alone. Behavioral test results will be correlated with axon growth in each animal. In Aim 3, we propose to determine the functionality of the serotonergic projections after our most effective treatment. First, changes in locomotion caused by pharmacologically blocking serotonergic receptors will be assessed. Second, we will determine reflex responses to somatic afferent stimulation following electrical stimulation of raphespinal pathways. Third, the release of 5-HT by descending fibers after the best treatment will be verified. Exploration of combined therapies to improve serotonergic fiber growth beyond the site of injury and determination of the role of the potentially improved growth on locomotion will lead to new clinical strategies in the future.