Objective:To evaluate the relationship between immunoglobulin heavy chain-binding protein (BIP) and Na v1.8 in peripheral nerve in a rat model of neuropathic pain. Methods:Forty-four SPF healthy male Sprague-Dawley rats, weighing 210-260 g, were used in this study.Neuropathic pain was induced by chronic constriction injury (CCI) in anesthetized rats.The experiment was performed in two parts.Experiment Ⅰ Twenty rats were divided into 2 groups ( n=10 each) using a random number table method: sham operation group (group Sham) and group CCI.Experiment Ⅱ Twenty-four rats were divided into 3 groups ( n=8 each) using a random number table method: sham operation group (group Sham), CCI plus normal saline group (group CCI+ NS) and CCI plus BIP inhibitor HA15 group (group CCI+ H). Starting from 4th day after surgery, 0.9% normal saline 1 ml was intraperitoneally injected in group CCI+ NS, and HA15 0.7 mg/kg was intraperitoneally injected in group H, once a day for 3 consecutive days.The mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were measured at 1 day before surgery and 3, 5 and 7 days after surgery (T 0-T 4), and the expression of BIP and Na v1.8 in dorsal root ganglion (DRG) and sciatic nerve was detected by Western blot on 7th day after completion of behavioral testing in two groups.The expression and colocalization of BIP and Na v1.8 in DRG and sciatic nerve were determined by immunofluorescence on 7th day after completion of behavioral testing in group Ⅰ, and the interaction between BIP and Na v1.8 was evaluated by co-immuno-precipitation. Results:Experiment Ⅰ Compared with group Sham, the MWT was significantly decreased, and TWL was shortened at T 1-T 4, the expression of Na v1.8 in DRG was down-regulated, the expression of BIP was up-regulated, and the expression of Na v1.8 and BIP in sciatic nerve was up-regulated in group CCI ( P<0.05), and BIP and Na v1.8 on the sciatic nerve were co-localized, BIP could co-precipitate Na v1.8 from DRG, and Na v1.8 could also coprecipitate BIP in group CCI.Experiment Ⅱ Compared with group Sham, the MWT was significantly decreased, and TWL was shortened at T 1-T 4, the expression of Na v1.8 in DRG was down-regulated, the expression of BIP was up-regulated, and the expression of Na v1.8 and BIP in sciatic nerve was up-regulated in group CCI+ NS ( P<0.05). Compared with group CCI+ NS, the MWT was significantly increased, and TWL was prolonged at T 3, 4, and the expression of Na v1.8 in DRG was down-regulated in group CCI+ H ( P<0.05). Conclusion:BIP can mediate the redistribution of Na v1.8 in peripheral nerve and is involved in the pathophysiological mechanism of neuropathic pain in rats.

Objective To evaluate the role of caspase-1 in the spinal cord in a rat model of incisional pain.Methods Eighteen adult male Sprague-Dawley rats,weighing 250-280 g,in which intrathecal catheters were successfully implanted,were divided into 3 groups (n =6 each) using a random number table:incision pain group (group Ⅰ),incision pain plus dimethyl sulfoxide group (group ID) and incision pain plus caspase-1 inhibitor (Ac-YVAD-CMK) group (group IA).At 10 min before establishment of the model,0.9％ normal saline 20 μl was intrathecally injected in group Ⅰ,dimethyl sulfoxide 20 μl was intrathecally injected and then the catheter was washed with 0.9％ normal saline 10 μl in group ID,and Ac-YVAD-CMK 1 nmol/μl (dissolved in 20 μl dimethyl sulfoxide) and then the catheter was washed with 0.9％ normal saline 10 μl in group IA.The mechanical paw withdrawal threshold (MWT) of the ipsilateral hind paw was measured at 2 h before intrathecal catheterization (T0),3 days after intrathecal catheterization (T1) and 2,6,24 and 48 h after establishment of model (T2-5).The rats were sacrificed after the last measurement of pain threshold at T5,and lumbar enlargement segments of the spinal cord were removed for detection of caspase-1 (p20) expression and interleukin-1beta (IL-1β) content by Western blot and enzyne-linked immunosorbent assay,respectively.Results Compared with the baseline at T0,the MWT was significantly decreased at T2-5 in Ⅰ and ID groups (P＜0.05),and no significant change was found in MWT at T1-5 in group IA (P＞0.05).Compared with Ⅰ and ID groups,the MWT at T2-5 was significantly increased at T2-5,and the caspase-1 (p20) protein expression and IL-1β content were decreased in group IA (P＜0.05).There was no significant difference in MWT,expression of caspase-1 (p20) protein or IL-1β content between group Ⅰ and group ID (P＞0.05).Conclusion The activation of caspase-1 in the spinal cord can promote the release of IL-1β and thus is involved in the incision pain in rats.