RESUMEN
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.
RESUMEN
Objective To investigate the relationship between G protein-coupled receptor kinase 6 (GRK6) and N-methyl-D-aspartate (NMDA) receptor in the mechanism study underlying motor complications in Parkinson's disease (PD).Methods The rat models (n= 25) of Parkinsonism related motor complications were established and were randomly divided into levodopa-induced dyskinesia (LID) group (n= 10,intraperitoneal injection of levodopa for 23 d),MK-801 treatment group (n= 10,intraperitoneal injection of MK-801 at day23 after intraperitoneal injection with levodopa for 22 days) and PD group (n= 5,intraperitoneal injection of vitamin C).Another 5 rats were served as controls (sham-operation group).The behavior changes of rats in MK-801 treatment group were observed,and the expression of GRK6 in the striate of rats was detected by immunohistochemistry and Western blot.Results After the chronic treatment with levodopa methyl ester,PD rats displayed abnormal involuntary movements,which was similar to levodopainduced dyskinesia in PD patients.Immunohistochemistry showed that GRK6-positive cells of lesion side were decreased in LID rats as compared with PD rats [(3.23±0.41 ) × 103 vs.(4.81 ± 1.31 ) ×103,P＜0.01].Rats in MK-801 treatment group displayed the decreased AIM scores and increased peak rotation,and the increased GRK6-positive cells of lesion side as compared with LID rats (P＜0.05).Western blot showed that the levels of GRK6 was 83.7% ±2.1% in PD group (presented as lesion side/unlesion side),76.8% ± 2.2% in LID group and 91.1% ± 2.7% in MK-801 treatment group (intergroups comparison:all P＜0.05).These results were in accordance with the results of immunohistochemistry.Conclusions Antagonist of NMDA receptor can be used to reduce the motor complications in rats.It may be due to increased GRK6 which inhibits the overactivation of glutamic acid receptors.
RESUMEN
Objective To investigate the effects of NO synthesis inhibition on pain threshold and binding capacity of NMDA receptor of hippocampus in rats. Methods Sixty-six SD rats of both sexes weighing (210 ? 20)g were randomly divided into 11 groups of six. Group I was used for determination of baseline values of pain threshold and binding capacity of NMDA receptor. In the five L-NAME groups (group Ⅱ-Ⅵ) 1% L-NAME in normal saline 50mg?kg-1 was given intraperitoneally (IP) . In the acute experiment pain threshold was determined 15 min (group Ⅱ ) and 30 min (group Ⅲ) after L-NAME IP injection. In the chronic experiment L-NAME 50mg?kg-1 was given IP twice a day for 1 day (group Ⅳ), 4 d (group Ⅴ) and 7 d (group Ⅵ) and pain threshold was measured 12h after last L-NAME administration. Group Ⅶ-Ⅺ served as control groups in which normal saline was given IP instead of L-NAME. Pain threshold was measured by response latencies following CO2 laser stimulation which was delivered to the medial surface of the ear. After determination of pain threshold the animals were decapitated and hippocampus was removed. The binding capacity of NMDA receptor with [3H] MK-801 was determined. Bmax and KD were determined by Scatchard analysis. Results There was no significant difference in pain threshold and binding capacity of NMDA receptor between group Ⅱ ,Ⅲ (acute experiment) and their control groups ( Ⅻ,Ⅷ). In chronic experiment pain threshold significantly increased after 1 and 4 d of L-NAME administration (group Ⅳ and Ⅴ) but return to the baseline value on the 7th day. NMDA receptor binding capacity increased in all three groups of chronic experiment. Bmax was significantly higher than the baseline value on the 4th and 7th day (group Ⅴ and Ⅵ). KD was significantly higher than the baseline value on the 4th day (group Ⅴ) but returned to the baseline on the 7th day (group Ⅵ) . Conclusions In chronic experiment NO synthesis inhibition can increase pain threshold to laser thermal nociceptive stimulation and induce changes in the affinity and density of NMDA receptor.