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

描述(由申请人提供)：我们的最终目标是开发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等人，2004年)，SC植入物、一次性向植入物上下的脊髓内注射cAMP和皮下注射Rolipram两周的三种组合可诱导5-羟色胺能纤维大量生长到植入物的脊髓尾部。在尾索5-羟色胺能轴突生长最好的组，运动测试成绩有明显改善。为了建立在这些结果的基础上，我们提出了使用相同损伤模型和SC移植的三个具体目标(Pearse等人，2004年)。在目标1中，我们将确定对cAMP升高最有效的投放部位(病变、中缝体节或两者)(通过测量纤维和评估活动)。众所周知，BDNF还可以促进5-羟色胺能轴突生长到脊髓尾侧的SC移植物中；因此，我们将使用相同的SCI范式来确定BDNF传递的最有效部位。在目标2中，我们建议测试cAMP升高和BDNF联合应用的可能性将比单独使用其中任何一种更有效。CAMP(最佳途径)和BDNF(最佳途径)的联合应用和5-羟色胺能轴突生长反应将与单独使用任何一种因素观察到的反应相比较。行为测试结果将与每只动物的轴突生长相关。在目标3中，我们建议在我们最有效的治疗后确定5-羟色胺能投射的功能。首先，将评估药物阻断5-羟色胺能受体引起的运动变化。其次，我们将确定电刺激神经通路后对躯体传入刺激的反射反应。第三，将验证最佳处理后下行纤维释放5-羟色胺的情况。探索联合治疗方法以改善损伤部位以外的5-羟色胺能纤维生长，并确定潜在改善的生长对运动的作用，将导致未来新的临床策略。

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.