The Role Of Spinal NRSF In Remifentanil-induced Hyperalgesia In Acute Incisional Pain And SMIR-induced Postoperative Chronic Pain

Objective To observe the effect of NRSF antisense oligonucleotide on remifentanil-induced hyperalgesia in a mouse model of incisional pain.MethodsPart one:According to the different procedures, Fifty-xix male KunMing mice were randomly divided into seven groups (n=8):group C (cerebral ventricle injection of artificial cerebrospinal fluid+a sham procedure+subcutaneous infusion of saline); group I (cerebral ventricle injection of artificial cerebrospinal fluid+a surgical incision+subcutaneous infusion of saline); group IR (cerebral ventricle injection of artificial cerebrospinal fluid+a surgical+subcutaneous infusion of remifentanil); group NAS (cerebral ventricle injection of NRSF antisense oligonucleotide+a sham procedure+subcutaneous infusion of saline); group I+NAS (cerebral ventricle injection of NRSF antisense oligonucleotide+a surgical incision+subcutaneous infusion of saline); group IR+NAS (cerebral ventricle injection of NRSF antisense oligonucleotide+a surgical incision+subcutaneous infusion of remifentanil); group IR+NMS (cerebral ventricle injection of NRSF missense oligonucleotide+a surgical incision+subcutaneous infusion of remifentanil). Behavioral tests were performed at 24 h before the surgery (baseline),2 h,6 h,24 h, and 48 h after the surgery. Western blot were analyzed just after behavioral tests at 48 h after the surgery.Part two:56 SD rats were divided randomly into 2 groups:sham group (group S, n-20) and model group (group M, n=36); 12 rats were selected randomly from group S and group M, and Paw withdrawal mechanical threshold (PWMT) were measured 1 day before SMIR surgery and day 4,7,10,14, after SMIR surgery. Group M was randomly divided into 3 groups again:group Mi and group M2、M3 (n=8). On the 3 day before operation, group M1 received intrathecal injection of cerebral ventricle injection 10 μl, group M3 received intrathecal injection of NRSF antisense oligonucleotide 10 μg/10 μl, and 8 rats in each group were selected randomly for measurement of PWMT on 1 day before SMIR surgery and day 4,7,10,14, after SMIR surgery. The spinal cord L4-5 segments were removed immediately under deep anesthesia with 3 rats at each time point, then stored at -80℃ until further processing. The expression of NRSF and MOR were detected by Western-Blot.ResultsPart one:Compared with group C, the PWMT and PWTL of group NAS had no significant difference (P>0.05). At 2 h,6 h,24 h, and 48 h after the surgery compared with group I [(0.64±0.13)g, (0.69±0.06)g, (0.78±0.10)g, (0.90±0.18)g], the PWMT of group IR [(0.34±0.14)g, (0.40±0.09)g,(0.33±0.09)g, (0.43±0.15)g] were significantly longer (P<0.05); compared with group I [(6.26±1.42)s, (6.49±1.38)s, (6.78±1.29)s, (7.55±1.28)s], the PWTL of group IR [(4.76±1.07)s, (3.78±0.63)s, (3.65±0.49)s, (4.09±0.77)s] were significantly longer (P<0.05). Compared with group I, there was no significant difference in PWMT and PWTL of group I+NAS (P>0.05). Compared with group IR, there was no significant difference in PWMT and PWTL of group IR+NMS. Compared with group IR, the PWMT of group IR+NAS were significantly longer at 2 hours [(0.59±0.18)g],6 hours [(0.68±0.16)g],24 hours [(0.73±0.09)g],48 hours [(0.89±0.15)g] (P<0.05) and the PWTL of group IR+NAS were significantly longer at 2 hours [(4.28±0.96)s],6 hours [(3.81±1.01)s],24 hours [(4.04±0.85)s], 48hours [(4.62±0.91)s] after operation respectively (P<0.05). there was no significant difference of spinal dorsal horn NRSF and MOR protein expression in among four groups.Part two:Compared with group S, the PWMT of group M were significantly decreased onl day before SMIR surgery and day 4,7,10,14 (P<0.05). At spinal cord level, the expression of NRSF was significantly increased (P<0.05), the expression of MOR was significantly decreased (P<0.05). There is no effect on pain behavior when intrathecal injection of cerebral ventricle injection (P>0.05).Conclusion NRSF antisense oligonucleotide intrathecally injected can effectively attenuate the hyperalgesia induced by remifentanil in a mouse model of incisional pain and chronic pain in rats induced by SMIR.