Relationship between NR2B and CaMK Ⅱ α in spinal cord during remifentanil-induced hyperalgesia in a rat model of incisional pain / 中华麻醉学杂志

ABSTRACT

Objective To evaluate the relationship between NR2B subunit-containing N-methyl-D-aspartate (NMDA) receptors (NR2B receptors) and Ca2+/calmodulin-dependent protein kinase Ⅱ α (CaMK Ⅱ α) in the spinal cord during remifentanil-induced hyperalgesia in a rat model of incisional pain (IP).Methods Forty male Sprague-Dawley rats in which intrathecal and caudal catheters were successfully placed,weighing 260-280 g,aged 2-3 months,were divided into 4 groups (n=10 each) using a random number table method:control group (group C),remifentanil plus IP group (group RI),NR2B antagonist Ro 25-6981 group (group Ro) and remifentanil plus IP plus Ro 25-6981 group (group RI+Ro).In group C,normal saline 0.1 ml was intrathecally injected,and 10 min later normal saline was infused for 60 min via the tail vein at a rate of0.1 ml · kg-1 · min-1.In group RI,normal saline 0.1 ml was intrathecally injected,and 10 min later remifentanil was infused for 60 min via the tail vein at a rate of 1.0 μg · kg-1 · min-1,and IP was established immediately after onset of remifentanil infusion.In group Ro,Ro 25-6981 (0.1 ml) 10 μg was intrathecally injected,and 10 min later normal saline was infused for 60 min via the tail vein at a rate of 0.1 ml · kg-1 · min-1.In group RI+Ro,Ro 25-6981 (0.1 ml) 10 μg was intrathecally injected,and 10 min later remifentanil was infused for 60 min via the tail vein at a rate of 1.0 μg · kg-1 · min-1,and IP was established immediately after onset of remifentanil infusion.The mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were measured at 24 h before intravenously infusing normal saline or remifentanil and at 2,6,24 and 48 h after the end of infusion (T0-4).The rats were sacrificed after the last behavioral test,and the L4-6 segment of the spinal cord was removed for determination of the expression of NR2B in total and membrane protein (tNR2B and mNR2B) and expression of CaMK Ⅱ α in total protein (tCaMK Ⅱ α) and phosphorylated CaMK Ⅱ α (pCaMKⅡα).The ratios of mNR2B/tNR2B and pCaMKⅡα/tCaMK Ⅱα were calculated.Results Compared with group C,the MWT was significantly decreased,TWL was shortened,the expression of tNR2B,mNR2B,tCaMKⅡα and pCaMKⅡα was up-regulated,and the ratios of mNR2B/tNR2B and pCaMK Ⅱ α/tCaMK Ⅱ α were increased in group RI (P＜0.05 or 0.01).Compared with group RI,the MWT was significantly increased,TWL was prolonged,the expression of tNR2B,mNR2B,tCaMKⅡα and pCaMKⅡα was down-regulated,and the ratios of mNR2B/tNR2B and pCaMK Ⅱ α/tCaMK Ⅱ α were decreased in group RI+ Ro (P＜0.05 or 0.01).Conclusion Enhanced function of NR2B can activate CaMKⅡα during remifentanil-induced hyperalgesia,which may be involved in the mechanism of remifentanil-induced hyperalgesia in a rat model of IP.