CaMKⅡ抑制剂阻抑脊髓背角C纤维诱发电位LTP的诱导和早期维持

CaMK Ⅱ inhibitor blocked the induction and early maintenance of LTP of C-fiber-evoked field potentials in spinal dorsal horn of adult rat

目的 :探讨钙调蛋白依赖性蛋白激酶Ⅱ (calmodulin dependentproteinkinaseII,CaMKⅡ )的高特异性抑制剂 (autocamtide 2 relatedinhibitorypeptide,AIP)在脊髓背角C纤维诱发电位长时程增强 (long termpotentiation ,LTP)的诱导和维持中的作用。 方法 :用单方波 (10～ 2 0V ,0 .5ms,1min/次 )刺激左侧坐骨神经 ,细胞外记录脊髓背角诱发电位。强直刺激 (40V ,0 .5ms ,10 0Hz,持续 1s ,以 10s间隔重复 4次 ,)坐骨神经诱导背角C纤维诱发电位LTP。在LTP诱导前后 ,在暴露的脊髓表面局部给予AIP ,观察其对LTP的影响。结果 :(1) 2 0 0 μmol/L的AIP不影响脊髓背角C纤维诱发电位的幅度 (n =4 ) ,但在强直刺激前 30min给予同样浓度的AIP可完全阻断脊髓背角LTP的诱导 (n =5 )。 (2 ) 2 0 0 μmol/L的AIP呈时间依赖性翻转脊髓背角LTP。在LTP诱导后 30min给予AIP ,LTP逐渐降低 ,于 3h降至对照水平 (n =6 ) ;在LTP诱导后 1h脊髓局部给予AIP ,10例动物中有 7例LTP被抑制 ;但同样浓度的AIP ,在LTP诱导后 3h ,不能翻转业已建立的LTP(n =6 ) ,且增加AIP的浓度至 5 0 0μmol/L也不能抑制脊髓背角LTP。结论 :CaMKⅡ参与脊髓背角C纤维诱发电位LTP的诱导和早期维持 ,但AIP对晚期LTP无抑制作用。

Objective: To investigate the role of autocamtide-2-related inhibitory peptide(AIP),a highly specific inhibitor of calcium/calmodulin-dependent protein kinase II (CaMKⅡ), in the induction and maintenance of long-term potentiation (LTP) of C-fiber evoked field potentials. Methods: Single square pulses (10-20 V,0.5 ms,1 min once) delivered to the sciatic nerve were used to evoke spinal field potentials. A conditioning tetanic stimulation (40 V,0.5 ms pulses at 100 Hz for 1 s repeated four times at 10 s intervals) was used to induce the spinal LTP. AIP was applied directly onto the recording segments of the spinal cord before and after LTP induction. Results: (1) AIP (200 μmol/L) , when applied 30 min before tetani,completely blocked LTP induction in all 6 rats tested. (2) AIP (200 μmol/L) reversed spinal LTP in a time-dependent manner: applied 30 min after LTP induction AIP depressed LTP in 7 rats,while applied 60 min after LTP induction,it depressed spinal LTP in 7 of 10 rats tested. The same concentration of AIP,applied at 3 h after LTP induction,however,did not affect spinal LTP in 6 rats. Conclusion: Activation of CaMK Ⅱ may be critical for the induction and the early-phase but not the later-phase maintenance of LTP of C-fiber evoked field potentials in spinal dorsal horn.