Objective To investigate the role of microglial activation in spinal cord in a rat model of persistent postoperative pain evoked by skin/muscle incision and retraction (SMIR) .Methods Seventy-two male SD rats weighing 200-250 g in which intrathecal (IT) catheter was successfully inserted were randomly divided into 3 groups ( n = 24 each) : group sham operation; group SMIR and group SMIR + FT minocycline (a specific microglia inhibitor) . The rat model of persistent postoperative pain evoked by SMIR was established according to the method described by Flatters. Pain behavior was assessed by paw mechanical withdrawal threshold ( MWT) to von Frey filament stimulation at 1 day before (T0,baseline) and 3, 7, 12, 22 and 32 days after operation (T1-5,) . Four animals were sacrificed at each time point in each group for detection of the expression of Iba-1 (a specific marker of microglia) in the spinal dorsal horn by immunofluorescence and the microglia was counted. Results MWT was significantly decreasedat T1-4, while the expression of Iba-1 and microglia counts in the spinal dorsal horn were significantly increased at T1, 2 by SMIR in group Ⅱ. IT minocycline significantly attenuated the hyperalgesia induced by SMIR at T1-4 and decreased Iba-1 expression and microglia counts at T1,2 in group Ⅲ. Conclusion Microglial activation in the spinal cord plays an important role in the development and maintenance of SMIR-evoked persistent postoperative pain in rats.

Objective To investigate the changes in acetylation of histone in the spinal dorsal horn in a rat model of persistent postoperative pain.Methods Ninety-six malc Sprague-Dawley rats,weighing 200-250 g,aged 6-8 weeks,were randomly divided into 2 groups (n=48 each) using a random number table:sham operation group (group S) and persistent postoperative pain group (group PPP).The rat model of persistent postoperative pain evoked by skin/muscle incision and retraction was established according to the method described by Flatters.After the rats were anesthetized with intraperitoneal chloral hydrate,the skin and superficial muscle of the medial thigh were incised and retractors inserted.This tissue was retracted for 1 h.The mechanical paw withdrawal threshold (MWT) was measured at 1 day before operation and 1,3,7,14,and 21 days after operation.Four animals were sacrificed in each group after measurement of MWT at each time point for detection of acetylated histone H3 (Ac-H3) and acetylated histone H4 (Ac-H4) expression (by Western blot analysis) and the number of Ac-H3 and Ac-H4 positive cells in the spinal cord horn (by immunofluorescence histochemistry).Results Compared with group S,the MWT was significantly decreased at 3,7,14 and 21 days after operation,the expression of Ac-H3 and Ac-H4b was significantly down-regulated at 3,7 and 14 days after operation,and the number of Ac-H3 and Ac-H4 positive cells was significantly decreased at 7,14 and 21 days after operation in group PPP (P＜0.05 or 0.01).The MWT,expression of Ac-H3 and Ac-H4b,and the number of Ac-H3 and Ac-H4 positive cells were significantly higher at 21 days after operation than at 14 days after operation in group PPP (P＜0.05).Conclusion Acetylation of histone in the spinal dorsal horn is decreased after operation,which may be involved in the development and maintenance of persistent postoperative pain in rats.

Objective To investigate the glial activation in the spinal cord in a rat model of persistent postoperative pain. Methods Forty-eight adult male SD rats weighing 200-250 g were randomly divided into 2 groups ( n = 24 each): group Ⅰ sham operation (group S) and group Ⅱ persistent postoperative pain. Persistent postoperative pain was evoked by skin/muscle incision and retraction (SMIR) as described by Flatters. Pawwithdrawal threshold to yon Frey hair stimulation was measured before operation (baseline) and at 1, 3, 12, 22and 32 d after establishment of the model. Four animals were sacrificed at each time point and lumbar segment of the spinal cord was removed for determination of expression of glial fibrillary acidic protein (GFAP) in the astrocytes by immunofluorescence histo-chemistry assay. Results The mechanical threshold started to decrease at 1 d after establishment of the model, and peaked at 12 d after establishment of the mode. Immunofluorescence histochemistry assay demonstrated that GFAP expression in the dorsal horn was significantly increased at 3 d after estabhshment of the model and reached the peak at 12 d and was maintained at the high level until 22 d after establishment of the model. Conclusion Glial activation is involved in the mechanism of persistent postoperative pain evoked by SMIR.

Objective It has been shown that protein kinase C (PKC), especially PKCy is involved in the nociceptive processing at the spinal level. This study was designed to investigate the effects of intrathecal (IT) morphine on PKCy immuno-reactivity in the spinal dorsal horn in a rat model of incisional pain. Methods Twenty-four male SD rats weighing 250-300 g were anesthetized with intraperitoneal pentobarbital 40 mg?kg-1. PE-10 catheter was inserted intrathecally to the lumbar region according to Yaksh. Five days later an incision of 1cm long was made in the plantar region of left hindpaw, parallel to the muscle under isoflurane anesthesia according to Brennan. The animals were randomly divided into 4 groups with 6 animals in each group : group Ⅰ sham-operation group received IT artificial cerebro-spinal fluid (ACSF) 20 ?l and 30 min later inhaled 1.4% isoflurane for S min but no incision was made; group Ⅱ received ACSF 20 ?l IT 30 min before incision was made; group Ⅲ post-incisional morphine group received morphine 5 ?g IT 30 min after incision and group Ⅳ pre-incisional morphine group received morphine 5 ?g IT 30 min before incision. The animals were sacrificed under general anesthesia 2 h after incision. The L4-5 segment of spinal cord was removed for determination of the expression of PKC? in the spinal dorsal horn by immuno-histochemical method.Results In group Ⅱ the PKC?-IR gray density in the spinal dorsal horn of the operated side was significantly higher than that of contralateral side and that in group Ⅰ( P

Objective To investigate the effects of intrathecal (IT) neostigmine on the excitatory amino-acid content in the L4-5 segment of spinal cord in a rat model of incisional pain. Methods Thirty-two male SD rats weighing 250-270 g were anesthetized with intraperitoneal pentobarbital 40 mg ? kg-1 . Intrathecal catheter was placed with the tip reaching the lumbar region according to the method of Yaksh. Five days later an 1 cm long incision was made in the plantar region of the right hind paw under isoflurane anesthesia according to the method of Brennan. Pain behavior was assessed at 1h after incision by cumulative pain score. The animals were randomly divided into four groups with 8 animals in each group: Ⅰsham operation group received IT artificial cerebro-spinal fluid (ACSF) 20 ?l but no incision was made in the hind paw; Ⅱ control group received ACSF 20 ?1 30 min before incision was made; Ⅲ postoperative neostigmine group received IT neostigmine 10 ?g 30 min after incision; Ⅳ preoperative neostigmine group received IT neostigmine 10 ?g before incision. 2h after incision the animals were decapitated and lumbar segment of spinal cord was removed for determination of aspartate and glutamate contents by high performance liquid chromatography (HPLC) with fluorescence detection. Results The cumulative pain scores in group Ⅱ were significantly higher than those in group Ⅰ (P 0.05) . Conclusion The decline in the increased excitatory amino-acid contents in spinal cord induced by incisional pain is involved in the mechanisms of analgesia provided by IT neostigmine.

To investigate the effects of ketamine on nitric oxide synathase(NOS)activity, nitrc oxide (NO) output and cyclic guanosine 3', 5'-monophosphate(cGMP)content in the rat brain. Method: Thirty two SD rats were divided randomly into control group and ketamine group. The aminals were administred intraperitoneally(ip)normal saline 10mg?kg~(-1) or ketamine 100mg?kg~(-1), respectively. NOS activity and NO output were assassed with spectrophotometric analysis, cGMP content was measured with radioimmunoassay, Result: Ketamine 100mg?kg~(-1) ip significantly inhibited NOS activity(P

Tn investigate the effects of propofol on Ca~(2+) ATPase activity in rat cerebral synaptic membrane. Method: Thirty SD rats were divided randomly into three groups. The aminals were administtered introperi toneally(ip) propofol 50mg?kg~(-1), 100mg?kg~(-1) or normal saline 10mg?kg~(-1)(control group), respectively. These rats were immediately decapitated after having disappeared righting reflex. In oredr to prepare synaptosomes, brain tissues were dissected on ice, then homogenized and centrifuged. Ca~(2+)-ATPase activity was assaed with spcetrophotometric analysis. Result: Propofol 100mg?kg~(-1) ip significantly inhibited Ca~(2+)-ATPase activity of cerebrocortical, brain stems and hippocampal synaptic membrane as compared with that of normal saline group(P

Objective:To investigate effects of propofol on nitric oxide synthase (NOS) activity and nitric oxide (NO)output of rat brain. Method: Sixteen SD rats were divided randomly into two groups. The animals were administered introperitoneally(ip) normal saline 10 ml?kg~(-1)(control group)or propofol 100mg?kg~(-1)(propofolgroup),respectively. These rats were decapitated immediately after having disappeared righting reflex. After rapid removal of cerebellum, brain stem,hippocampus and cerebral cortex,tissues were homogenized and centrifuged. NOS activity and NO output were assayed with spectrophotometric analysis. Result: In propofol group,NOS activity was significantly inhibited, NO outpul was significantly reduced in cerebellum, brain stem,hippoeampus and cerebral cortex as compared with those of control group(P

Objective To investigate the effects of isoflurane on cyclic adenosine monophosphate (cAMP ) content of brain in the rats. Methods Fourty SD rats were allocated randomly to 5 groups: no administration(control group,n=8), inhalation of 1.4% isoflurane until losing of righting reflex(loss of righting reflex group,n=8), inhalation of 1.4% isoflurane lasting 30 min(anesthesia group,n=8) ,righting reflex recovery after cessation of 30-min inhalation of 1.4% isoflurane (recoveryⅠ group,n=8) and 30 min after cessation of 30-min inhalation of 1.4% isoflurane (recovery Ⅱ group,n=8). The rats of each group were decapitated at the end of procedures to measure the cAMP content of brain tissue with competitive protein binding assay.Results As compared with that in control group,the cerebrocortical cAMP content only in anesthesia group significantly increased by 49% (P

Objective To investigate the effects of intrathecal neostigmine on nitric oxide synthase (NOS) activity, nitric oxide (NO) production and cyclic guanosine 3',5' monophosphate (cGMP) content of the spinal cord in a rat model of incisional pain Methods Male SD rats weighing 250 300g were anesthetized with intraperitoneal pentobarbital sodium 40 mg?kg -1 Intrathecal(IT) catheter was implanted and the tip of the cathter reached the lumbar region, according to the method of Yaksh Incision was made in the plantar aspect of the left hindpaw under 1 4% isoflurane anesthesia, according to the method of Brennan 64 male SD rats were were divided randomly into four groups GroupⅠ received IT 0 9% NaCl 20 ?l and 30 min later inhaled 1 4% isoflurane for 5 min but no incision was made Group Ⅱ received IT 0 9% NaCl 20 ?l 30 min before incision Group Ⅲ received IT neostigmine 10?g(10?l) 30 min after incision GroupⅣreceived IT neostigmine 10?g(10?l) 30 min before incision In group Ⅲ and Ⅳ 0 9%NaCl 10 ?l was flushed through IT catheter after IT neostigmine administration A cumulative pain score was utilized to assess pain behavior The animals were decapitated 2h after incision and the spinal cord was immediately removed and lumbar enlargement of the spinal cord was dissected on ice NOS activity, NO production and cGMP content were measured by spectrophotometry and radioimmunoassy Results Cumulative pain score in group Ⅲ and group Ⅳ was significantly lower than that in groupⅡ(P