Role of the cAMP Pathway in a Chronic Muscle Pain Model

cAMP通路可被细胞外信号、激素和神经递质激活，在疼痛传递中起重要作用。cAMP通路激活蛋白激酶A （PKA）。然后PKA磷酸化NMDA受体，使其更有效，并磷酸化cAMP-response-element-element-binding protein (CREB)，导致基因转录。以往的研究都是针对短期痛觉过敏并伴有明显的组织损伤和炎症。cAMP在慢性肌肉疼痛中的作用尚不清楚。具体目的#1将确定阻断cAMP通路是否能逆转慢性肌肉疼痛模型中的机械性痛觉过敏。这将通过鞘内给予腺苷酸环化酶或PKA抑制剂阻断cAMP途径，然后测量对机械性痛觉过敏的影响来确定。具体目标#2将确定NMDA受体和CREB是否在慢性肌肉疼痛的脊髓中磷酸化。这将通过免疫组织化学染色和western blot检测1)NMDA受体（NR1）的PKA位点和2)CREB的磷酸化来确定。预计在慢性疼痛中磷酸化会增加，阻断PKA会减少机械性痛觉过敏以及CREB和NMDA受体的磷酸化。

The cAMP pathway, which can be activated by extracellular signals, hormones and neurotransmitters, plays a significant role in pain transmission. The cAMP pathway activates protein kinase A (PKA). PKA then phosphorylates the NMDA receptor, making it more effective, and the cAMP-response-element-element-binding protein (CREB), resulting in gene transcription. Previous studies all investigates short- term hyperalgesia with significant tissue damage and inflammation. The role of cAMP in chronic muscle pain is unknown. Specific aim #1 will determine if blockade of the cAMP pathway reverses mechanical hyperalgesia in a chronic muscle pain model. This will be determined by blocking the cAMP pathway by intrathecally administering inhibitors of 1) adenylate cyclase or 2) PKA and then measuring the effect on mechanical hyperalgesia. Specific aim #2 will determine if the NMDA receptor and CREB are phosphorylated in the spinal cord in chronic muscle pain. This will be determined by conducting immunohistochemical stains and western blots for phosphorylation of 1) the PKA site of the NMDA receptor (NR1) and 2) CREB. It is expected that phosphorylation will increase in the chronic pain and that blocking PKA will decrease mechanical hyperalgesia and the phosphorylation of CREB and the NMDA receptor.