ABSTRACT
Objective To evaluate the effect of intrathecal oxytocin on neuropathic pain in rats.Methods Thirty-six SPF male Sprague-Dawley rats,aged 4-6 weeks,weighing 100-150 g,were divided into 4 groups (n =9 each) using a random number table:control group (group C),neuropathic pain group (group NP),neuropathic pain plus normal saline group (group NPN) and neuropathic pain plus oxytocin group (group NPO).The neuropathic pain model was made by partial sciatic nerve injury in NP,NPN and NPO groups.In group NPO,oxytocin l0 μl (0.1 μg) was intrathecally injected on the day of establishing the model and 1 and 2 days after establishing the model,and then normal saline 10 μl was given for tube sealing at 9 a.m.and 4 p.m.every day.In group NPN,normal saline 20 μl was given for tube sealing at the corresponding time points.The mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were measured at 1 day before establishing the model and 1,2,3,4,5,6 and 7 days after establishing the model.The expression of the astrocyte marker glial fibrillary acidic protein (GFAP) and a specific marker of microglia ionized calcium-binding adaptor molecule 1 (IBa-1) was detected by Western blot at 1 day before establishing the model and 3 and 7 days after establishing the model.Results Compared with group C,the MWT was significantly decreased,TWL was shortened and the expression of GFAP and IBa-1 was up-regulated at each time point in NP and NPN groups (P＜0.05).There was no significant difference in MWT,TWL GFAP and IBa-1 at each time point between group NPN and group NP (P＞0.05).Compared with NP group,MWT was significantly increased at 2-4 days after establishing the model,TWL was prolonged at 1-4 days after establishing the model,the expression of IBa-1 was down-regulated on 3 days after establishing the model,and the expression of GFAP was downregulated on 3 and 7 days after establishing the model in group NPO (P＜0.05).Conclusion Oxytocin can reduce neuropathic pain,and the mechanism may be related to inhibiting activation of glial cells in the spinal cord of rats.
ABSTRACT
BACKGROUND: Schwann cells play an important role in axonal growth and myelin sheath formation of the peripheral nerve. Whether Schwann cells play the same role in the spinal cord had attracted considerable attention. Microencapsulation technology as an effective immune isolation technique can effectively keep Schwann cell activity to play the repair effect of Schwann cell in the spinal cord.OBJECTIVE: To observe the changes of myelin sheath in the injured transection of rats after transplantation of the alginic acid microencapsulated Schwann cells.DESIGN, TIME AND SETTING: The randomized controlled animal experiment was performed at the Basic Medical School of Nanchang University from March 2005 to February 2008.MATERIALS: Sciatic nerve trunk was obtained from adult rabbits to harvest Schwann cells in vitro using repeatedly differential velocity adherent technique, and to prepare Schwann cell suspension and microencapsulated Schwann cell suspension.METHODS: A total of 146 adult Sprague Dawley rats were used to establish models of right hemi-transection damage at T_(10) level and randomly assigned to four groups: simple injury group (n=44), cell transplantation group (n=44), microencapsulated cell transplantation group (n=44) and normal control group (n=14). At 1, 3, 7,14 and 28 days following surgery, 8 rats were selected from each group at each time point (2 from the normal control group) for perfusion and fixation. Spinal cord tissue was collected to make paraffin section, and then subjected to hematoxylin-eosin staining and Loyez myelin staining. In addition, 2 rats were selected from each group at 2 and 8 weeks. The spinal cord tissue was fixed, embedded in Epon816, stained using uranyl acetate and aluminum citrate, and then observed using an electron microscope.MAIN OUTCOME MEASURES: Neuron number and survival were observed surrounding the damaged region. Structural changes in the myelin sheath from spinal cord white substance at the damage site were measured.RESULTS: At 1 and 3 days following spinal cord injury, spinal neurons were degenerated and necrotic at damaged site, with reduced number of myelin sheath, loose structure, but above-mentioned was rare in the cell transplantation and microencapsulated cell transplantation groups. At 7 days, the reduced number of myelin sheath, with damaged structure was seen. The microencapsulated cell transplantation group was light. At 14 days, number of neurons was increased, with increased cell body, especially in the microencapsulated cell transplantation group. At 28 days, neurons gradually recovered, myelin sheath was gradually complete, with increased number in the microencapsulated cell transplantation group. There were significant differences compared with the simple injury and cell transplantation groups (P < 0.01). At 8 weeks, abundant myelin sheath was repaired, with new myelin sheath in the microencapsulated cell transplantation group.CONCLUSION: Microcapsule has immune isolation effects. Microencapsulated rabbit Schwann cells can promote the repair of rat spinal cord neurons and axonal myelinization.