ABSTRACT
Objective To explore the mechanism of N-methyl-D-aspartic acid ( NMDA) receptor/MAPK/cAMPresponse element binding protein ( CREB) pathway involved in pain-related aversion mediated by anterior cingulate cortex. Methods A total of 42 healtlry SD rats were randomly divided into control group (Ctrl) , normal saline(NS) injection group (NS) , complete freund adjuvant (CFA) model group ( CFA ) , injected CFA into the soles of the foot and injected NS into rostral part of anterior cingulate cortex (rACC)group (CFA+NS) , injected NS into the soles of the foot and injected NS into rACC group (NS+NS) , injected CFA into the soles of the foot and injected NMDA receptor antagonist ( APV ) into rACC group (CFA+APV) , injected NS into the soles of the foot and injected APV into rACC group ( NS + APV ) with 6 rats in each group. Rats avoidance score was analysised and rat thermal foot contraction latency ( PWL) ws alserved, the expression of NMDA receptor in rACC region was detected by immunohistochemical staining, the expression of NMDA receptor, phosphorylated ERK( p-ERK) and phosphorylated CREB ( p - CREB ) in rACC region was detected by immunofluorescent staining, the number of Nissl bodies in rACC region was observed by Nissl staining, and the expression of NMDA receptor, MAPK, CREB, ERK, p-ERK, p-CREB, synaptosomal-associated protein 25 interaction protein 30 (SIP30) protein in rACCregion was detected by Western blotting, and Real-time PCR was used to detect the mRNA expression of NMDA receptor, MAPK, CREB and ERK in the rACC region. Results Compared with the Ctrl group, the avoidance score and PWL decreased significantly and the expression of NMDA receptor, MAPK and CREB increased significantly in the CFA group (P<0. 05). Compared with the CFA+NS group, the number of Nissl bodies in CFA+APV and NS+APV groups increased significantly, while the expression of NMDA receptor, MAPK, CREB, p-ERK and p-CREB decreased significantly in NS+NS and NS+APV groups (P<0. 05). Conclusion NMDA receptor-MAPK-CREB signal pathway in rACC is involved in painrelated aversion, and inhibition of NMDA can reduce pain-related negative aversion.
ABSTRACT
Objective To investigate the effect of bone cancer pain on emotion and NMDA re-ceptor NR2B subunit expression level in anterior cingulate cortex (ACC)in rats.Methods One hun-dred and fifty healthy male Wistar rats weighing 200-250 g aged 3 months old were randomly divided into 3 groups (n = 50 in each group):sham operation group (group S),bone cancer pain group (group BCP),RO25-6981 group (group RO).The BCP model was established by inoculating Walker 256 breast cancer cells into right intra-tibial.Rats in group S were given the same dose of d-hanks. Group RO was injected intraperitoneally with RO25-6981 (5 mg/kg/d)on the day of inoculation, while rats in the group S and group BCP were given the same dose of normal saline.Mechanical with-drawal threshold (MWT)and thermal withdrawal latency (TWL)of right hind legs were measured on day 7,10,14 after inoculation respectively.Elevated plus-maze test was carried out to investigate the effect of bone cancer pain on emotion in rats after pain threshold detection,then the percentage of the times entering the open arms (OE)and the percentage of the time staying in the open arms (OT) duration the total period were evaluated.Then the anterior cingulate cortex tissue was removed to e-valuate the NR2B protein and mRNA expression levels by RT-PCR,Western blot and immunofluo-rescence methods on day 14 after elevated plus-maze test.Results All the parameters did not differ with significant difference between group S and group RO.MWT decreased and TWL shortened on day 7,10,14 after inoculation in group BCP compared with those before inoculation and those of group S and group RO.OE and OT in group BCP reduced remarkably than those before inoculation and those of group S and group RO.Relative absorbance of NR2B mRNA,the expression of NR2B pro-tein,average NR2B relative fluorescence intensity value is obviously higher than that of group S and group RO (P <0.05).Conclusion Bone cancer pain can induce pain-related aversion and anxiety-like behavior of rats,and the mechanism may be related to the high expression of NR2B in anterior cingu-late cortex.