Background Gabapentin has been widely and successfully used in the clinic for many neuropathic pain syndromes since last decade, however its analgesic mechanisms are still elusive. Our study was to investigate whether Ca^2＋/calmodulin-dependent protein kinase Ⅱ （CaMKⅡ） contributes to the analgesic effect of gabapentin on a chronic constriction injury （CCI） model. Methods Gabapentin （2%, 100 mg/kg） or saline （0.5 ml/100 g） was injected intraperitoneally 15 minutes prior to surgery and then every 12 hours from postoperative day 0-4 to all rats in control, sham and CCI groups. The analgesic effect of gabapentin was assessed by measuring mechanical allodynia and thermal hyperalgesia of rats. Expression and activation of CaMKⅡ were quantified by reverse-transcriptional polymerase chain reaction and Western blotting. Results The analgesic effect of gabapentin on mechanical allodynia and thermal hyperalgesia was significant in the CCI model, with maximal reduction reached on postoperative day 8. Gabapentin decreased the expression of the total CaMKⅡ and phosphorylated CaMKⅡ in CCI rats. Conclusion The analgesic effect of gabapentin on CCI rats may be related to the decreased expression and phosphorylation of CaMKⅡ in the spinal cord.
MA Lu-luLIU WeiHUANG Yu-guangYANG NanZUO Ping-ping
Objective To observe the effects of PSD95 gene specific siRNAs on neuropathic pain relief, neuron viability, and postsynaptic calcium/calmodulin-dependent protein kinase IIα (CaMKIIα) phosphorylation in vitro and in vivo. Methods Gene-specific siRNAs of rat PSD95 were synthesized chemically for transfection. Adult male Sprague-Dawley (SD) rats were randomly divided into 3 groups: nave group (n=6), sham group (n=6), and sciatic nerve chronic constriction injury (CCI) group (n=24). The CCI group was further divided into 4 groups (n=6 in each group), which were pretreated with normal saline, transfection vehicle, negative control siRNAs, and PSD95 gene specific siRNAs respectively. All the subgroups received corresponding agents intrathecally for 3 days, started one day before the CCI of sciatic nerve. Both mechanical allodynia and thermal hyperalgesia were measured on post-operative day 3 and 7. PSD95 gene silenced NG108-15 cells were further stimulated by glutamate, with the cell viability and the expression/phosphorylation of CaMKIIα measured by MTT cell proliferation assay and Western blot, respectively. Results The siRNAs decreased PSD95 mRNA level significantly both in vivo and in vitro. Neuropathic pain rats pretreated with PSD95 gene specific siRNAs exhibited significant elevation in the mechanical withdrawal threshold and paw withdrawal thermal latency, without affecting the baseline nociception. PSD95 gene silencing enhanced neuronal tolerance against the glutamate excitotoxicity, meanwhile the phosphorylation of CaMKIIα Thr286 was attenuated. Conclusion Pre-emptive administration of PSD95 gene specific siRNAs may attenuate the central sensitization CaMKIIα-related signaling cascades, leading to the relief of neuropathic pain.
Le Shen Xu Li Wen Chen Li Xu Wei Liu Xue-rong Yu Yu-guang Huang
